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  • 1.
    Blom, Henning
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Jerve, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Qu, Qingming
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Chen, Donglei
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Märss, Tiiu
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
    Dupret, Vincent
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The affinity of Lophosteus and the evolution of osteichthyan characters2011Conference paper (Other academic)
  • 2.
    Blom, Henning
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Jerve, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Qu, Qinming
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Chen, Dong Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Märss, Tiiu
    Tallinn University of Technology.
    Dupret, Vincent
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The affinity of Lophosteus  and the evolution of osteichthyan characters2011Conference paper (Refereed)
  • 3.
    Chen, Dong Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Tafforeau, Paul
    Estonian Marine Institute, University of Tartu.
    Märss, Tiiu
    Estonian Marine Institute, University of Tartu.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Development of cyclic shedding teeth from semi-shedding teeth: the inner dental arcade of the stem osteichthyan Lophosteus 2017In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 4, no 5, article id 161084Article in journal (Refereed)
    Abstract [en]

    The numerous cushion-shaped tooth-bearing plates attributed to the stem-group osteichthyan Lophosteus superbus, which are argued here to represent the ancient form of inner dental arcade, display a unique and presumably primitive way of tooth shedding by basal hard tissue resorption. They carry regularly spaced, recumbent, gently recurved teeth arranged in transverse tooth files that diverge towards the lingual margin of the cushion. Three-dimensional (3D) reconstruction from propagation phase contrast synchrotron microtomography (PPC-SRμCT) reveals remnants of the first-generation teeth embedded in the basal plate that have never been discerned in any taxa. These teeth were shed by semi-basal resorption with the periphery of their bases retained as dentine rings. The rings are highly overlapped, which evidences tooth shedding prior to adding the next first-generation tooth. Later teeth at the same sites underwent cyclical replacing and shedding through basal resorption, producing stacks of buried resorption surfaces separated by bone of attachment. The number and spatial arrangement of resorption surfaces elucidates that basal resorption of replacement teeth had taken place at the older tooth sites before the addition of the youngest first-generation teeth at the lingual margin. Thus the replacement tooth buds cannot have been generated by a single permanent dental lamina, but must have arisen either from successional dental laminae associated with the predecessor teeth, or directly from the dental epithelium of these teeth. The virtual histological dissection of these Late Silurian microfossils broadens our understanding of the development of the gnathostome dental systems and the acquisition of the osteichthyan-type of tooth replacement. 

  • 4.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Dental Development of the Stem Osteichthyan Andreolepis hedei Revealed by Three-dimensional Synchrotron Virtual Paleohistology2013In: Program and Abstracts: Society of Vertebrate Paleontology 73rd Annual meeting, 2013, p. 103-103Conference paper (Other academic)
  • 5.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Dental Development of the Stem Osteichthyan Andreolepis hedei Revealed by Three-dimensional Synchrotron Virtual Paleohistology2013Conference paper (Other academic)
  • 6.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Three-dimensional histology of tooth cushions of Lophosteus from the Upper Silurian of Estonia2011In: Abstracts: The 2nd Wiman meeting: Carl Wiman's Legacy: 100 years of Swedish Palaeontology: Uppsala 17–18 November 2011 / [ed] Benjamin P. Kear and Michael Streng, 2011, p. 5-6Conference paper (Other academic)
    Abstract [en]

    Lophosteus superbus from the Late Silurian of Estonia is one of the oldest and most plesiomorphic osteichthyans described to date. Unfortunately at present it is known only from fragmented dermal microremains. The affinities of Lophosteus are therefore controversial with the taxon placed as either basal to both actinopterygians and sarcopterygians, or ambiguously linked to either placoderms or acanthodians. To confound matters further, the character states diagnosing actinopterygians and sarcopterygians have recently been brought into question, and even monophyly of the traditional placoderm and acanthodian clades has been challenged. As a possible stem osteichthyan, Lophosteus could thus be central to our understanding of early gnathostome evolution and the origin of the osteichthyan body plan. Often the best-preserved, although incompletely documented, elements of Lophosteus are tooth cushions. These tooth-bearing arched ossicles could arguably be homologous with the parasymphysial tooth whorls in chondrichthyans, acanthodians, and sarcopterygians, or even the parasymphysial tooth plates in tetrapodomorphs. High-resolution synchrotron scans of 6 isolated tooth cushions from the Upper Silurian of Estonia has permitted a detailed reconstruction of their three-dimensional architecture. The absence of an enamel layer and the presence of large hollows (bigger than normal osteocytes) in the deepest lamellar layer confirmed assignment of the specimens to Lophosteus. The external surface displays irregularly distributed denticles and there are large parallel vessels running horizontally on the basal bone that feed the denticle rows internally. The odontodes have two distinct generations (with successive odontodes accreted between those of the preceding buried generation) and are organised in a similar manner to those found on Lophosteus scales. This new histological data on vascularization provides insight into early gnathostome tooth patterning and could contribute to future phylogenetic assessments.

  • 7.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, 6 Rue Jules Horowitz, F-38043 Grenoble, France..
    Tafforeau, Paul
    European Synchrotron Radiat Facil, 6 Rue Jules Horowitz, F-38043 Grenoble, France..
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    The stem osteichthyan Andreolepis and the origin of tooth replacement2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 539, no 7628, p. 237-+Article in journal (Refereed)
    Abstract [en]

    The teeth of gnathostomes (jawed vertebrates) show rigidly patterned, unidirectional replacement that may or may not be associated with a shedding mechanism. These mechanisms, which are critical for the maintenance of the dentition, are incongruently distributed among extant gnathostomes. Although a permanent tooth-generating dental lamina is present in all chondrichthyans, many tetrapods and some teleosts, it is absent in the non-teleost actinopterygians. Tooth-shedding by basal hard tissue resorption occurs in most osteichthyans (including tetrapods) but not in chondrichthyans. Here we report a three-dimensional virtual dissection of the dentition of a 424-million-year-old stem osteichthyan, Andreolepis hedei, using propagation phase-contrast synchrotron microtomography, with a reconstruction of its growth history. Andreolepis, close to the common ancestor of all extant osteichthyans, shed its teeth by basal resorption but probably lacked a permanent dental lamina. This is the earliest documented instance of resorptive tooth shedding and may represent the primitive osteichthyan mode of tooth replacement.

  • 8.
    Clarac, Francois
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Scheyer, Torsten M.
    Univ Zurich, Paleontol Inst & Museum, Karl Schmid Str 4, CH-8006 Zurich, Switzerland.
    Desojo, Julia B.
    Consejo Nacl Invest Cient & Tecn, Div Paleontol Vertebrados, Museo La Plata, Paseo Bosque S-N,B1900FWA, La Plata, Buenos Aires, Argentina.
    Cerda, Ignacio A.
    Consejo Nacl Invest Cient & Tecn, La Plata, Buenos Aires, Argentina;Univ Nacl Rio Negro, Inst Invest Paleobiol & Geol, Museo Carlos Ameghino, Belgrano 1700, RA-8300 Cipolletti, Rio Negro, Argentina.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. European Synchrotron Radiat Facil, 71 Ave Martyrs,CS-40220, F-38043 Grenoble, France.
    The evolution of dermal shield vascularization in Testudinata and Pseudosuchia: phylogenetic constraints versus ecophysiological adaptations2020In: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 375, no 1793, article id 20190132Article in journal (Refereed)
    Abstract [en]

    Studies on living turtles have demonstrated that shells are involved in the resistance to hypoxia during apnea via bone acidosis buffering; a process which is complemented with cutaneous respiration, transpharyngeal and cloacal gas exchanges in the soft-shell turtles. Bone acidosis buffering during apnea has also been identified in crocodylian osteoderms, which are also known to employ heat transfer when basking. Although diverse, many of these functions rely on one common trait: the vascularization of the dermal shield. Here, we test whether the above ecophysiological functions played an adaptive role in the evolutionary transitions between land and aquatic environments in both Pseudosuchia and Testudinata. To do so, we measured the bone porosity as a proxy for vascular density in a set of dermal plates before performing phylogenetic comparative analyses. For both lineages, the dermal plate porosity obviously varies depending on the animal lifestyle, but these variations prove to be highly driven by phylogenetic relationships. We argue that the complexity of multi-functional roles of the post-cranial dermal skeleton in both Pseudosuchia and Testudinata probably is the reason for a lack of obvious physiological signal, and we discuss the role of the dermal shield vascularization in the evolution of these groups. This article is part of the theme issue 'Vertebrate palaeophysiology'.

  • 9.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. Australian Natl Univ, Dept Appl Math, Res Sch Phys & Engn, Canberra, ACT, Australia..
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, Grenoble, France..
    Goujet, Daniel
    UPMC Paris 6, CNRS, MNHN, CR2P UMR 7207,Sorbonne Univ,Museum Natl Hist Nat, Paris, France..
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    The internal cranial anatomy of Romundina stellina Orvig, 1975 (Vertebrata, Placodermi, Acanthothoraci) and the origin of jawed vertebrates: Anatomical atlas of a primitive gnathostome2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 2, article id e0171241Article in journal (Refereed)
    Abstract [en]

    Placoderms are considered as the first jawed vertebrates and constitute a paraphyletic group in the stem-gnathostome grade. The acanthothoracid placoderms are among the phylogenetically most basal and morphologically primitive gnathostomes, but their neurocranial anatomy is poorly understood. Here we present a near-complete three-dimensional skull of Romundina stellina, a small Early Devonian acanthothoracid from the Canadian Arctic Archipelago, scanned with propagation phase contrast microtomography at a 7.46 mu m isotropic voxel size at the European Synchrotron Radiation Facility, Grenoble, France. This is the first model of an early gnathostome skull produced using this technique, and as such represents a major advance in objectivity compared to past descriptions of placoderm neurocrania on the basis of grinding series. Despite some loss of material along an oblique crack, most of the internal structures are remarkably preserved, and most of the missing structures can be reconstructed by symmetry. This virtual approach offers the possibility to connect with certainty all the external foramina to the blood and nerve canals and the central structures, and thus identify accurate homologies without destroying the specimen. The high level of detail enables description of the main arterial, venous and nerve canals of the skull, and other perichondrally ossified endocranial structures such as the palatoquadrate articulations, the endocranial cavity and the inner ear cavities. The braincase morphology appears less extreme than that of Brindabellaspis, and is in some respects more reminiscent of a basal arthrodire such as Kujdanowiaspis.

  • 10.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Being Romundina stellina Ørvig, 1975 (Vertebrate, Placodermi, Acanthothoraci): itracranial anatomy of one of the deepest gnathostomes revealed by synchrotron tomograpy in phase contrast protocole2012In: / [ed] Malvesy, T., Gauthrot, M., Fuchs, C., Berthoz, A., Blieck, A., Becker, D., Buffetaut, E., Mazin, J. -M.,, Montbéliard, 2012, p. 19-19Conference paper (Refereed)
    Abstract [en]

    Dans la peau de Romundina stellina Ørvig, 1975 (Vertebrata, Placodermi, Acanthothoraci)

    Anatomie crânienne d'un des premiers gnathostomes révélée par tomographie synchrotron en contraste de phase

     Being Romundina stellina Ørvig, 1975  (Vertebrata, Placodermi, Acanthothoraci)

    Intracranial anatomy of one of the deepest gnathostomes revealed by synchrotron tomography in phase contrast protocole

     

     

    The acanthothoracid placoderms (armored fishes) are the most basal and primitive gnathostomes (jawed vertebrates; 1). However, their endocranial morphology is poorly understood, and only one genus (Brindabellaspis) has been described thoroughly (2).

    Here we present the 3D reconstruction of a subcomplete skull of Romundina stellina Ørvig, 3, from the Lochkovian of Prince of Wales Island, Canadian Arctic Archipelago. The specimen was imaged in 3D with propagation phase contrast microtomography (4) on the ID19 beamline of the ESRF, using a 7.45 µm isotropic voxel size.

    Most features are properly preserved and most of the missing structures can be virtually rebuilt by symmetry. Another advantage of this virtual approach is the possibility of connecting with certainty all the external foramina to the blood and nerve canals and the central/internal structures, and hence to identify accurate homologies without destroying the specimen. Ørvig’s original assumptions can now be checked with confidence.

    The vasculature of the dermal bones, rendered in detail, allowed a better understanding of plate growth. It permits the visualization of dermal bone establishment over perichondral bone (5).

    The high level of details of this model reveals that between the trigeminal and vagus nerve (and the inner ears), the perichondral bone wrapping the endocranial cavity shows a “lace” pattern, unknown so far in vertebrates (presumably because of the lack of data). The significance of this character is unclear, but it is definitely not an artifact of taphonomy or scanning.

     

    References

    1          Janvier, P. Early Vertebrates. Clarendon Press edn, Vol. 1 (Oxford Science Publications, 1996).

    2          Young, G. C. A new Early Devonian placoderm from New South Wales, Australia, with a discussion of placoderm phylogeny. Palaeontographica (A) 167, 10–76 (1980).

    3          Ørvig, T. Description, with special reference to the dermal skeleton, of a new Radotinid arthrodire from the Gedinnian of Arctic Canada. Extrait des Colloques internationaux du Centre National de la Recherche Scientifique - Problèmes actuels de Paléontologie - Evolution des Vertébrés 218, 41–71 (1975).

    4          Tafforeau, P. et al. Applications of X-ray synchrotron microtomography for non-destructive 3D studies of paleontological specimens. Applied Physics A - Materials Science & Processing 83, 195–202 (2006).

    5          Dupret, V., Sanchez, S., Goujet, D., Tafforeau, P. & Ahlberg, P. Bone vascularization and growth in placoderms (Vertebrata): the example of the premedian plate of Romundina stellina Ørvig, 1975 Comptes Rendus Palevol 9, 369–375 (2010).

     

     

  • 11.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Fossil early vertebrates shed lights on the origin of the gnathostome face2013In: Program and Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona, Spain, 2013, p. 245-245Conference paper (Refereed)
    Abstract [en]

    Jawless cyclostomes and jawed gnathostomes show very different face patterns. Cyclostomes have a single median nasohypophysial duct, an anterior hypophysis and a short telencephalon, while gnathostomes have a pair of nasal sacs opening externally, a more posterior separate hypophysis open in the palate and a longer telencephalon.

    Embryonic processes differ as well. In cyclostomes, premandibular crest cells migrate forwards either side of the nasohypophysial placode to form the upper lip; in gnathostomes they migrate between the hypophysial and nasal placodes to form the trabecular region. Supraoptic neural crest remains posterior to the nasohypophysial duct in cyclostomes; it moves forward to create the nasal capsules in gnathostomes.

    Some fossil forms illustrate a transition between these two patterns.

    The jawless galeaspid Shuyu (-430 Ma) has a nasohypophysial duct, short telencephalon, and anteriorly oriented hypophysis, but the paired nasal sacs and hypophysis are separated by a rudimentary trabecula.

    The jawed primitive placoderm Romundina (-415 Ma) shows a cranial cavity reminiscent of that of Shuyu (anteriorly directed hypophysis, very short telencephalon). The trabecular region is long and wide, the nasal capsule is small and located far behind the tip of the snout but just in front of the orbits. We interpret these features as uniquely primitive among gnathostomes. The premandibular crest of Romundina formed a trabecular region extending as anteriorly as the tip of the snout (like in extant cyclostome and the fossil Shuyu). The position of the nasal capsule suggests that the supraoptic crest had not migrated forwards.

    We suggest that the evolutionary sequence for the creation of the extant gnathostome face from a cyclostome pattern involved 1) separation of the nasal and hypophysial placodes (galeaspids), 2) loss of the nasohypophysial duct (placoderms), and 3) lengthening of the telencephalon and the migration of the nasal capsules to the snout tip.

  • 12.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Fossils of early vertebrates and the evolution of the gnathostome face revealed by Synchrotron imaging2013In: Programme and Abstracts / [ed] Stig Walsh, Nick Fraser, Stephen Brusatte, Jeff Liston, Vicen Carrió, Edinburgh, U.K., 2013, p. 21-21Conference paper (Refereed)
    Abstract [en]

    Cyclostomes and gnathostomes have distinct face patterns. Cyclostomes possess a median nasohypophysial duct, an anterior hypophysis and a short telencephalon, contra gnathostomes possessing a pair of nasal sacs opening externally, a separate posterior hypophysis opening onto the palate and a long telencephalon. Embryonic development also differs. In cyclostomes, premandibular crest cells migrate forwards either side of the nasohypophysial placode, forming an upper lip; in gnathostomes they migrate between the hypophysial and nasal placodes forming the trabecular region. Supraoptic neural crest remains posterior to the nasohypophysial duct in cyclostomes but moves forward to create the nasal capsules in gnathostomes. Fossil stem gnathostomes illustrate a transitional sequence between these two patterns: 1) The galeaspid Shuyu (jawless stem gnathostome): nasohypophysial duct, short telencephalon, and anteriorly oriented hypophysis as in a cyclostome, but paired nasal sacs and hypophysis separated by a rudimentary trabecula. 2) The primitive placoderm Romundina (jawed stem gnathostome): short telencephalon, anteriorly directed hypophysis, trabecular region long and wide, nasal capsule located far behind the tip of the snout but just in front of the orbits. These features are interpreted as uniquely primitive among gnathostomes. The trabeculae of Romundina form an extensive precerebral region resembling the upper lip of extant cyclostomes and Shuyu. The position of the nasal capsule suggests that the supraoptic crest had not migrated forwards. 3) The arthrodire Kujdanowiapsis (a more derived placoderm): short telencephalon and vertically oriented hypophysis. The trabecula has been shortened anteriorly, making the nasal capsule terminal. These positional relationships are maintained in crown gnathostomes.

  • 13.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Internal structures of the skull of Romundina stellina Ørvig 1975 (Vertebrata, Placodermi, Acanthothoraci) revealed by phase contrast synchrotron scanning2011In: CAVEPS Perth 2011: Conference on Australasian Vertebrate Evolution Palaeontology and Systematics, Perth, April 27th-30th : programme, abstracts / [ed] Geological Survey of Western Australia, East Perth, W.A: Geological Survey of Western Australia , 2011, p. 30-30Conference paper (Refereed)
  • 14.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Intracranial anatomy of Romundina stellina Ørvig 1975 (Vertebrata, Placodermi, Acanthothoraci) revealed by phase contrast synchrotron imaging2011In: Abstracts: The 2nd Wiman meeting Carl Wiman's Legacy: 100 years of Swedish Palaeontology: Uppsala 17–18 November 2011 / [ed] Benjamin P. Kear, Michael Streng, 2011, p. 6-6Conference paper (Other academic)
    Abstract [en]

    Acanthothoracid placoderms are considered amongst the most basal of primitive gnathostomes. However, their endocranial morphology is poorly understood, and only one genus (Brindabellaspis) has been described in detail. Here we present a synchrotrongenerated 3D reconstruction of a nearly complete skull of Romundina stellina, a taxon established in 1975 by the Norwegian-born Swedish palaeontologist Tor Ørvig based on remains from the Lochkovian (Lower Devonian) of Prince of Wales Island, Canadian Arctic Archipelago. The specimen was imaged with propagation phase contrast microtomography on the ID19 beamline of the ESRF, using a 7.45 µm isotropic voxel size. Most structural features of the fossil are very well preserved, allowing missing elements to be virtually rebuilt by symmetry. This permitted reconnection of the external foramina and blood vessel/nerve canals, and alignment of the central/internal structures. Expanding on Ørvig’s original interpretations, our virtual models show the vasculature of the skull bones, and indicate establishment of successive dermal over perichondral bone layers. The perichondral bone wrapping the endocranial cavity, in between the trigeminal and vagus nerve (and the inner ears), shows a “lace” pattern, which is otherwise unknown in vertebrates (presumably because of the lack of data). The significance of this trait is unclear but it is not an artifact of taphonomy or scanning.

  • 15.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Structures intra-crâniennes de Romundina stellina Ørvig 1975 (Vertebrata, Placodermi, Acanthothoraci) révélé par tomographie synchrotron en contraste de phase2012Conference paper (Refereed)
    Abstract [fr]

    Les placodermes acanthothoracides sont parmi les vertébrés gnathostomes les plus basaux phylogénetiquement et morphologiquement. Néanmoins, une bonne connaissance anatomie crânienne fait défaut, et à ce jour un seul genre (Brindabellaspis) a été décrit en détails. Nous présentons le modèle en 3 dimensions d’un crâne presque complet de Romundina stellina, un petit acanthothoracide du Dévonien inférieur de l’Archipel Arctique Canadien, décrit originellement par Ørvig (1975). Le spécimen a été microtomographié sur la ligne de faisceau ID 19 de l’ESRF de Grenoble (European Synchrotron Radiation Facility), en protocole de contraste de phase, avec un voxel isotrope de 7,45 micromètres.

    Malgré une cassure oblique, la plupart des structures peuvent être reconstruites par symétrie. Chaque nerf crânien peut être suivi entre la cavité encéphalique et les murs du neurocrâne composés d’os périchondral. Il en est de même pour les vaisseaux sanguins. La détermination des homologies en est donc facilitée, tout en assurant la non destruction du spécimen. Les hypothèses d’homologies formulées par Ørvig peuvent être traitées en toute confidence.

    La couche d’os périchondrale entourant la cavité encéphalique n’est pas homogène mais présente un aspect en dentelle entre les nerfs trijumeaux (V) et vague (X) ; il en est de même pour les oreilles internes, dont les canaux semi-circulaires ne sont pas ossifiés du tout latéralement et dorsalement. Cet aspect en dentelle n’est ni un artefact de fossilisation, de préservation ou de modélisation, et n’a jamais été retrouvé sur aucun autre vertébré (mais l’échantillonnage à cette résolution fait encore cruellement défaut).

    Les canalicules nerveux reliés aux neuromastes de la ligne latérale permettent de retracer leur origine à une branche du nerf facial (VII). Les deux oreilles internes ont été reconstruites avec précision et montrent une morphologie primitive.

    Le réseau vasculaire de l’os dermique a été reconstruit en détails, et permet de mettre en évidence les limites de plaques du toit crânien, invisibles autrement. Ce réseau vasculaire est relié à des veines drainant la bordure de la boîte crânienne ou à une branche de la veine jugulaire. La courbure de ces vaisseaux autour de l’oreille interne pourrait démarquer la limite entre la capsule otique et l’arc hyoïdien qui s’y attachait.

    D’un point de vue général, la morphologie de la boîte crânienne et de ses structures associées paraît moins primitive (et moins extrême) que celle de Brindabellaspis, mais rappelle au contraire plus les structures observées chez le placoderme arthrodire Kujdanowiaspis, plus dérivé.

    Ces différences mettent en lumière les premiers stades de l’évolution du crâne des placodermes, donc des gnathostomes. 

  • 16.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The cranial anatomy of Romundina stellina Ørvig, 1975 (Vertebrata, Placodermi, Acanthothoraci) revealed by phase contrast synchrotron scanning2010Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    The acanthothoracid placoderms are among the most phylogenetically basal and morphologically primitive gnathostomes. However, their endocranial anatomy is not well understood; only one genus, Brindabellaspis, has been described in detail. Here we present a near-complete three-dimensional skull of Romundina stellina, a small Early Devonian acanthothoracid from the Canadian Arctic Archipelago, scanned at the European Synchrotron Radiation Facility, Grenoble, France, at a 7.45 µm resolution using propagation phase contrast. Despite some loss of material along an oblique crack, most of the internal structures are remarkably preserved. Each postethmoid cranial and craniospinal nerve can be followed between the well-preserved endocranial cavity and the walls of the perichondrally ossified neurocranium. The minute nerve canals that supplied the neuromast organs of the sensory line system are preserved and can in the postorbital area be traced directly to a branch of the facial nerve. Both inner ears are present. The vascular mesh of the dermal bones has been reconstructed in detail, rendering visible the dermal plate boundaries of the skull roof, and is shown to connect to larger internal veins that drain to the edge of the braincase or into the jugular vein canal. The curvature of the latter vessels parallels the outer surface of the inner ear and may demarcate the boundary between otic capsule proper and applied hyoid arch material. Overall, the braincase morphology appears less extreme (and less primitive?) than that of Brindabellaspis, in some respects more reminiscent of a primitive arthrodire such as Kujdanowiaspis. These differences may illuminate the earliest stages of placoderm cranial evolution.

  • 17.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The origin of the jawed vertebrate face: new insights from a synchrotron scanned skull of the primituve placoderm Romundina2013In: Program and abstracts / [ed] Maxwell, E., Miller-Camp, J., Anemone, R.,, Los Angeles, U.S.A., 2013, p. 118-118Conference paper (Other academic)
    Abstract [en]

    Jawless cyclostomes and jawed gnathostomes show very different face patterns.Cyclostomes have a single median nasohypophysial duct, an anterior hypophysis and ashort telencephalon, while gnathostomes have a pair of nasal sacs opening externally, amore posterior separate hypophysis opening in the palate and a longer telencephalon.Embryonic processes differ as well. In cyclostomes, infraorbital premandibular crest cellsmigrate forwards either side of the nasohypophysial placode to form the upper lip; ingnathostomes they migrate between the hypophysial and nasal placodes to form thetrabecular-ethmoid region. Supraoptic neural crest remains posterior to thenasohypophysial duct in cyclostomes; it moves forward to create the nasal capsules ingnathostomes. Some fossil forms illustrate a sequenced transition between these twopatterns. The Silurian galeaspid (jawless stem gnathostome) Shuyu has a nasohypophysialduct, a short telencephalon, and an anteriorly oriented hypophysis, but the paired nasalsacs and hypophysis are separated by a rudimentary trabecula. A synchrotron scannedskull of the primitive Early Devonian placoderm (jawed stem gnathostome) Romundinashows a cranial cavity reminiscent of that of Shuyu (anteriorly directed hypophysis, veryshort telencephalon). The trabecular-ethmoid region is long and wide, extending anteriorto the small nasal capsule which is located just in front of the orbits. We interpret thesefeatures as uniquely primitive among gnathostomes. In size and position the trabecularethmoidregion of Romundina resembles the upper lip of cyclostomes and Shuyu,suggesting a cyclostome-like pattern of proliferation coupled with a gnathostome-likemigration path for the premandibular crest. The position of the nasal capsule suggests thatthe supraoptic crest had not migrated forwards. A new phylogenetic analysis suggeststhat the evolutionary sequence for the creation of the extant gnathostome face from acyclostome ancestral pattern involved 1) separation of the nasal and hypophysialplacodes (galeaspids: Shuyu), 2) loss of the nasohypophysial duct (basal placoderms:antiarchs, Brindabellaspis, Romundina), 3) shortening and narrowing of the trabecularethmoidregion, the nasal capsule becoming anterior (derived placoderms such asarthrodires); 4) lengthening of the telencephalon (crown gnathostomes). Galeaspid facialanatomy appears closer to gnathostomes than that of osteostracans, but it is unclearwhether osteostracans are primitive or autapomorphic in this respect.

  • 18.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The Placoderm Romundina and the Origin of the Gnathostome Face2013In: The Making of a Vertebrate / [ed] Toyama, Y., Ito, A., Kobe, Japan, 2013, p. 110-111Conference paper (Refereed)
    Abstract [en]

    Facial anatomy differs fundamentally between extant jawless and jawed vertebrates (cyclostomes and gnathostomes). Cyclostomes have a median nasohypophysial duct; gnathostomes have separate nasal sacs opening externally, and a palatal hypophysis. Premandibular crest cells migrate forwards either side of the nasohypophysial placode to form the upper lip in cyclostomes, but between the hypophysial and nasal placodes to form the trabecular region in gnathostomes1,2. Supraoptic neural crest remains posterior to the nasohypophysial duct in cyclostomes but moves forward to create the nasal capsules of gnathostomes1,2. In cyclostomes the telencephalon is much shorter than in gnathostomes and the hypophysis is relatively anterior. The galeaspid Shuyu, a 430 million year old jawless vertebrate, partly bridges the gap between these facial architectures3. Shuyu has a nasohypophysial duct, short telencephalon, and anteriorly oriented hypophysis, but the nasal sacs and hypophysis are separated by a rudimentary trabecula.

                          Here we present the placoderm Romundina, a 415 million year old jawed vertebrate that represents a further transitional step. Its cranial cavity is similar to that of Shuyu, with an anteriorly directed hypophysis and very short telencephalon. The trabecular region is exceptionally long and wide whereas the nasal capsule (demarcated by a fissure) is small and located far behind the tip of the snout. The upper jaw articulates with the side of the trabecular region to its anterior end, without contacting the nasal capsule. We interpret these features as uniquely primitive among gnathostomes. The premandibular crest of Romundina formed a trabecular region, but like the upper lip of cyclostomes and Shuyu it was a large structure reaching the tip of the snout. The position of the nasal capsule suggests that the supraoptic crest had not migrated forwards. We suggest that during the creation of the gnathostome face, separation of the nasal and hypophysial placodes was followed by loss of the nasohypophysial duct, with lengthening of the telencephalon and migration of the nasal capsules to the snout tip as the final step.

  • 19.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Muséum National D'Histoire Naturelle, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The Placoderm Romundina and the Origin of the Gnathostome Face2013Conference paper (Refereed)
    Abstract [en]

    Facial anatomy differs fundamentally between extant jawless and jawed vertebrates (cyclostomes and gnathostomes). Cyclostomes have a median nasohypophysial duct; gnathostomes have separate nasal sacs opening externally, and a palatal hypophysis. Premandibular crest cells migrate forwards either side of the nasohypophysial placode to form the upper lip in cyclostomes, but between the hypophysial and nasal placodes to form the trabecular region in gnathostomes1,2. Supraoptic neural crest remains posterior to the nasohypophysial duct in cyclostomes but moves forward to create the nasal capsules of gnathostomes1,2. In cyclostomes the telencephalon is much shorter than in gnathostomes and the hypophysis is relatively anterior. The galeaspid Shuyu, a 430 million year old jawless vertebrate, partly bridges the gap between these facial architectures3. Shuyu has a nasohypophysial duct, short telencephalon, and anteriorly oriented hypophysis, but the nasal sacs and hypophysis are separated by a rudimentary trabecul. Here we present the placoderm Romundina, a 415 million year old jawed vertebrate that represents a further transitional step. Its cranial cavity is similar to that of Shuyu, with an anteriorly directed hypophysis and very short telencephalon. The trabecular region is exceptionally long and wide whereas the nasal capsule (demarcated by a fissure) is small and located far behind the tip of the snout. The upper jaw articulates with the side of the trabecular region to its anterior end, without contacting the nasal capsule. We interpret these features as uniquely primitive among gnathostomes. The premandibular crest of Romundina formed a trabecular region, but like the upper lip of cyclostomes and Shuyu it was a large structure reaching the tip of the snout. The position of the nasal capsule suggests that the supraoptic crest had not migrated forwards. We suggest that during the creation of the gnathostome face, separation of the nasal and hypophysial placodes was followed by loss of the nasohypophysial duct, with lengthening of the telencephalon and migration of the nasal capsules to the snout tip as the final step.

     

    1. Kuratani, S. et al. Phil. Trans. R. Soc. Lond. B 356, 1615-1632 (2001).

    2. Kuratani, S. et al. Nature (in press, doi:10.1038/nature11794).

    3. Gai, Z. et al. Nature 476, 324-327 (2011).

  • 20.
    Dupret, Vincent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Goujet, Daniel
    Tafforeau, Paul
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    A primitive placoderm sheds light on the origin of the jawed vertebrate face2014In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 507, no 7493, p. 500-503Article in journal (Refereed)
    Abstract [en]

    Extant vertebrates form two clades, the jawless Cyclostomata (lampreys and hagfishes) and the jawed Gnathostomata (all other vertebrates), with contrasting facial architectures(1,2). These arise during development from just a few key differences in the growth patterns of the cranial primordia: notably, the nasal sacs and hypophysis originate from a single placode in cyclostomes but from separate placodes in gnathostomes, and infraoptic ectomesenchyme migrates forward either side of the single placode in cyclostomes but between the placodes in gnathostomes(3-8). Fossil stem gnathostomes preserve cranial anatomies rich in landmarks that provide proxies for developmental processes and allow the transition from jawless to jawed vertebrates to be broken down into evolutionary steps(7,9-12). Here we use propagation phase contrast synchrotron microtomography to image the cranial anatomy of the primitive placoderm (jawed stem gnathostome) Romundina(13), and show that itcombines jawed vertebrate architecture with cranial and cerebral proportions resembling those of cyclostomes and the galeaspid (jawless stem gnathostome) Shuyu(11). This combination seems to be primitive for jawed vertebrates, and suggests a decoupling between ectomesenchymal growth trajectory, ectomesenchymal proliferation, and cerebral shape change during the origin of gnathostomes.

  • 21. Gand, Georges
    et al.
    Tuysuz, Okan
    Steyer, J. Sebastien
    Allain, Ronan
    Sakinc, Mehmet
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sengor, A. M. Celal
    Sen, Sevket
    New Permian tetrapod footprints and macroflora from Turkey (Cakraz Formation, northwestern Anatolia): Biostratigraphic and palaeoenvironmental implications2011In: Comptes rendus. Palevol, ISSN 1631-0683, E-ISSN 1777-571X, Vol. 10, no 8, p. 617-625Article in journal (Refereed)
    Abstract [en]

    New tetrapod footprints belonging to the ichnogenus Hyloidichnus have been discovered in Turkey for the first time, in the lower part of the Cakraz Formation (Northwestern Anatolia) and together with macrofloral imprints of Annularia and Stigmaria. These discoveries confirm the Permian age of the fossiliferous red beds in which the coniferophyte Walchia was previously recorded. Based on the stratigraphic range of Annularia,Stigmaria and Hyloidichnus known elsewhere, a Cisuralian age is proposed for these beds. These new ichno- and macrofloral remains, together with the sedimentological data (mudcracks, rain drops) suggest the presence of captorhinid reptiles living in a palustrine floodplain environment, and under a warm, seasonal climate alternating between humid and relatively long dry seasons. These climatic conditions may have permitted the migration of these captorhinids through Laurasia during the Permian.

  • 22. Germain, Damien
    et al.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Janvier, Philippe
    Tafforeau, Paul
    The presumed hagfish Myxineidus gononorum from the Upper Carboniferous of Montceau-les-Mines (Saone-et-Loire, France): New data obtained by means of Propagation Phase Contrast X-ray Synchrotron Microtomography2014In: Annales de Paléontologie, ISSN 0753-3969, E-ISSN 1778-3666, Vol. 100, no 2, p. 131-135Article in journal (Refereed)
    Abstract [en]

    The re-examination of the presumed hagfish Myxineidus gononorum from the Carboniferous of Montceaules-Mines by means of propagation phase contrast X-ray synchrotron microtomography confirms the presence of two series of non-mineralized denticles arranged in chevrons in the oral region. It also indicates the presence of possible traces of post-mortem mineralized soft tissues. A peculiar zone of less X ray-absorbing matter around the animal suggests the presence of an enlarged, lamprey-like oral disc. Re-interpreting Myxineidus as a lamprey would be in better agreement with the reputedly fresh-water environment of the Montceau-les-Mines Lagerstatte. 

  • 23.
    Jerve, Anna
    et al.
    Imperial Coll London, Biol Dept, Silwood Pk Campus,Buckhurst Rd, Ascot SL5 7PY, Berks, England.
    Bremer, Oskar
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, 71 Ave Martyrs, F-38000 Grenoble, France.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Morphology and histology of acanthodian fin spines from the late Silurian Ramsåsa E locality, Skåne, Sweden2017In: Palaeontologia Electronica, ISSN 1935-3952, E-ISSN 1094-8074, Vol. 20, no 3, article id 56AArticle in journal (Refereed)
    Abstract [en]

    Comparisons of acanthodians to extant gnathostomes are often hampered by the paucity of mineralized structures in their endoskeleton, which limits the potential preservation of phylogenetically informative traits. Fin spines, mineralized dermal structures that sit anterior to fins, are found on both stem-and crown-group gnathostomes, and represent an additional potential source of comparative data for studying acanthodian relationships with the other groups of early gnathostomes. An assemblage of isolated acanthodian fin spines from the late Silurian Ramsasa site E locality (southern Sweden) has been reconstructed in 3D using propagation phase contrast synchrotron X-ray microtomography (PPC-SR mu CT). The aim is to provide morphological and taxo-nomical affinities for the spines by combining morphology and histology with the taxo-nomical framework previously established for the site mainly based on isolated scales. The high-resolution scans also enable investigations of the composition and growth of acanthodian fin spines when compared to similar studies of extinct and extant gnathostomes. In total, seven fin spine morphotypes that have affinities to both Climatiidae Berg 1940 and Ischnacanthiformes Berg 1940 are described. The majority are interpreted as median fin spines, but three possible paired spines are also identified. The spines display differences in their compositions, but generally agree with that presented for climatiids and ischnacanthiforms in previous studies. Their inferred growth modes appear to be more similar to those of fossil and extant chondrichthyan fin spines than to those described from placoderms and stem-osteichthyans, which is congruent with the emerging view of acanthodians as stem-chondrichthyans.

  • 24.
    Jerve, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Imperial Coll London, Dept Life Sci, Ascot, Berks, England.
    Qu, Qingming
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Univ Ottawa, Ctr Adv Res Environm Genom, Ottawa, ON, Canada.
    Sanchez, Sophie
    Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, Grenoble, France.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Three-dimensional paleohistology of the scale and median fin spine of Lophosteus superbus (Pander 1856)2016In: PeerJ, ISSN 2167-8359, E-ISSN 2167-8359, Vol. 4, article id e2521Article in journal (Refereed)
    Abstract [en]

    Lophosteus superbus is one of only a handful of probable stem-group osteichthyans known from the fossil record. First collected and described in the late 19th century from the upper Silurian Saaremaa Cliff locality in Estonia, it is known from a wealth of disarticulated scales, fin spines, and bone fragments. In this study we provide the first description of the morphology and paleohistology of a fin spine and scale from Lophosteus using virtual thin sections and 3D reconstructions that were segmented using phase-contrast synchrotron X-ray microtomography. These data reveal that both structures have fully or partially buried odontodes, which retain fine morphological details in older generations, including sharp nodes and serrated ridgelets. The vascular architecture of the fin spine tip, which is composed of several layers of longitudinally directed bone vascular canals, is much more complex compared to the bulbous horizontal canals within the scale, but they both have distinctive networks of ascending canals within each individual odontode. Other histological characteristics that can be observed from the data are cell spaces and Sharpey's fibers that, when combined with the vascularization, could help to provide insights into the growth of the structure. The 3D data of the scales from Lophosteus superbus is similar to comparable data from other fossil osteichthyans, and the morphology of the reconstructed buried odontodes from this species is identical to scale material of Lophosteus ohesaarensis, casting doubt on the validity of that species. The 3D data presented in this paper is the first for fossil fin spines and so comparable data is not yet available. However, the overall morphology and histology seems to be similar to the structure of placoderm dermal plates. The 3D datasets presented here provide show that microtomography is a powerful tool for investigating the three-dimensional microstructure of fossils, which is difficult to study using traditional histological methods. These results also increase the utility of fin spines and scales suggest that these data are a potentially rich source of morphological data that could be used for studying questions relating to early vertebrate growth and evolution.

  • 25.
    Jerve, Anna
    et al.
    Imperial Coll London, Biol Dept, Silwood Pk Campus, Ascot, Berks, England.
    Qu, Qinming
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Univ Ottawa, Ctr Adv Res Environm Genom, Ottawa, ON, Canada.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, Grenoble, France.
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Haitina, Tatjana
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Vascularization and odontode structure of a dorsal ridge spine of Romundina stellina Ørvig 19752017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 12, article id e0189833Article in journal (Refereed)
    Abstract [en]

    There are two types of dermal skeletons in jawed vertebrates: placoderms and osteichthyans carry large bony plates (macromery), whereas chondrichthyans and acanthodians are covered by small scales (micromery). Fin spines are one of the last large dermal structures found on micromeric taxa and offer a potential source of histology and morphology that can be compared to those found on macromeric groups. Dermal fin spines offer a variety of morphology but aspects of their growth modes and homology are unclear. Here, we provide detailed descriptions of the microstructure and growth of a dorsal ridge spine from the acanthothoracid placoderm, Romundina stellina, using virtual three-dimensional paleohistological datasets. From these data we identify several layers of dentine ornamentation covering the lateral surfaces of the spine and reconstructed their growth pattern. We show that this spine likely grew posteriorly and proximally from a narrow portion of bone located along the leading edge of the spine. The spine is similarly constructed to the scales with a few exceptions, including the absence of polarized fibers distributed throughout the bone and the presence of a thin layer of perichondral bone. The composition of the spine (semidentine odontodes, dermal bone, perichondral bone) is identical to that of the Romundina dermal plates. These results illustrate the similarities and differences between the dermal tissues in Romundina and indicate that the spine grew differently from the dentinous fin spines from extant and fossil chondrichthyans. The morphology and histology of Romundina is most similar to the fin spine of the probable stem osteichthyan Lophosteus, with a well-developed inner cellular bony base and star-shaped odontodes on the surface. Results from these studies will undoubtedly have impact on our understanding of fossil fin spine histology and evolution, contributing to the on-going revision of early gnathostome phylogeny.

  • 26.
    Johanson, Zerina
    et al.
    Nat Hist Museum, Dept Earth Sci, London, England..
    Smith, Moya
    Nat Hist Museum, Dept Earth Sci, London, England.;Kings Coll London, Dent Inst, Tissue Engn & Biophoton, London, England..
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. European Synchrotron Radiat Facil, Grenoble, France..
    Senden, Tim
    Australian Natl Univ, Res Sch Phys & Engn, Dept Appl Math, Canberra, ACT 2601, Australia..
    Trinajstic, Kate
    Curtin Univ, Environm & Agr, Kent St, Perth, WA, Australia..
    Pfaff, Cathrin
    Univ Vienna, Dept Palaeontol, Vienna, Austria..
    Questioning hagfish affinities of the enigmatic Devonian vertebrate Palaeospondylus2017In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 4, no 7, article id 170214Article in journal (Refereed)
    Abstract [en]

    Palaeospondylus gunni Traquair, 1890 is an enigmatic Devonian vertebrate whose taxonomic affinities have been debated since it was first described. Most recently, Palaeospondylus has been identified as a stem-group hagfish (Myxinoidea). However, one character questioning this assignment is the presence of three semicircular canals in the otic region of the cartilaginous skull, a feature of jawed vertebrates. Additionally, new tomographic data reveal that the following characters of crown-group gnathostomes (chondrichthyans + osteichthyans) are present in Palaeospondylus: a longer telencephalic region of the braincase, separation of otic and occipital regions by the otico-occipital fissure, and vertebral centra. As well, a precerebral fontanelle and postorbital articulation of the palatoquadrate are characteristic of certain chondrichthyans. Similarities in the structure of the postorbital process to taxa such as Pucapampella, and possible presence of the ventral cranial fissure, both support a resolution of Pa. gunni as a stem chondrichthyan. The internally mineralized cartilaginous skeleton in Palaeospondylus may represent a stage in the loss of bone characteristic of the Chondrichthyes.

  • 27.
    Kamska, Viktoriia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Daeschler, Edward B.
    Drexel Univ, Acad Nat Sci, 1900 Benjamin Franklin Pkwy, Philadelphia, PA 19103 USA.
    Downs, Jason P.
    Drexel Univ, Acad Nat Sci, 1900 Benjamin Franklin Pkwy, Philadelphia, PA 19103 USA;Delaware Valley Univ, Dept Biol, 700 East Butler Ave, Doylestown, PA 18901 USA.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Tafforeau, Paul
    European Synchrotron Radiat Facil, 71 Ave Martyrs, F-38000 Grenoble, France.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, 71 Ave Martyrs, F-38000 Grenoble, France;Univ Paris 06, Sorbonne Univ, Ctr Rech Paleobiodiversite & Paleoenvironm, Museum Natl Hist Nat,CNRS, 57 Rue Cuvier,CP38, F-75005 Paris, France.
    Long-bone development and life-history traits of the Devonian tristichopterid Hyneria lindae2019In: Earth and environmental science transactions of the Royal Society of Edinburgh, ISSN 1755-6910, E-ISSN 1755-6929, Vol. 109, no 1-2, p. 75-86Article in journal (Refereed)
    Abstract [en]

    Hyneria lindae is one of the largest Devonian sarcopterygians. It was found in the Catskill Formation (late Famennian) of Pennsylvania, USA. The current study focuses on the palaeohistology of the humerus of this tristichopterid and supports a low ossification rate and a late ossification onset in the appendicular skeleton. In addition to anatomical features, the large size of the cell lacunae in the cortical bone of the humerus mid-shaft may suggest a large genome size and associated neotenic condition for this species, which could, in turn, be a partial explanation for the large size of H. lindae. The low metabolism of H. lindae revealed here by bone histology supports the hypothesis of an ambush predatory behaviour. Finally, the lines-of-arrested-growth pattern and late ossification of specimen ANSP 21483 suggest that H. lindae probably had a long juvenile stage before reaching sexual maturity. Although very few studies address the life-history traits of stem tetrapods, they all propose a slow limb development for the studied taxa despite different ecological conditions and presumably distinct behaviours. The bone histology of H. lindae would favour the hypothesis that a slow long-bone development could be a general character for stem tetrapods.

  • 28.
    Knoll, Fabien
    et al.
    ARAID Fdn Conjunto Paleontol Teruel Dinopolis, Teruel 44002, Spain.;Univ Manchester, Sch Earth & Environm Sci, Manchester M13 9PL, Lancs, England..
    Chiappe, Luis M.
    Nat Hist Museum Los Angeles Cty, Dinosaur Inst, Los Angeles, CA 90007 USA. Uppsala Univ, Dept Organismal Biol, S-75236 Uppsala, Sweden..
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. European Synchrotron Radiat Facil, F-38000 Grenoble, France..
    Garwood, Russell J.
    Univ Manchester, Sch Earth & Environm Sci, Manchester M13 9PL, Lancs, England.;Nat Hist Museum, Dept Earth Sci, Cromwell Rd, London SW7 5BD, England..
    Edwards, Nicholas P.
    Univ Manchester, Sch Earth & Environm Sci, Manchester M13 9PL, Lancs, England.;SLAC Natl Accelerator Lab, Stanford Synchrotron Radiat Lightsource, Menlo Pk, CA 94025 USA..
    Wogelius, Roy A.
    Univ Manchester, Sch Earth & Environm Sci, Manchester M13 9PL, Lancs, England..
    Sellers, William I.
    Univ Manchester, Sch Earth & Environm Sci, Manchester M13 9PL, Lancs, England..
    Manning, Phillip L.
    Univ Manchester, Sch Earth & Environm Sci, Manchester M13 9PL, Lancs, England.;Coll Charleston, Dept Geol & Environm Geosci, Charleston, SC 29424 USA..
    Ortega, Francisco
    Univ Nacl Educ Distancia, Fac Ciencias, E-28040 Madrid, Spain..
    Serrano, Francisco J.
    Nat Hist Museum Los Angeles Cty, Dinosaur Inst, Los Angeles, CA 90007 USA. Uppsala Univ, Dept Organismal Biol, S-75236 Uppsala, Sweden.;Univ Malaga, Fac Ciencias, Malaga 29010, Spain..
    Marugan-Lobon, Jesus
    Nat Hist Museum Los Angeles Cty, Dinosaur Inst, Los Angeles, CA 90007 USA. Uppsala Univ, Dept Organismal Biol, S-75236 Uppsala, Sweden.;Univ Autonoma Madrid, Fac Ciencias, E-28049 Madrid, Spain..
    Cuesta, Elena
    Univ Autonoma Madrid, Fac Ciencias, E-28049 Madrid, Spain..
    Escaso, Fernando
    Univ Nacl Educ Distancia, Fac Ciencias, E-28040 Madrid, Spain..
    Luis Sanz, Jose
    Univ Autonoma Madrid, Fac Ciencias, E-28049 Madrid, Spain..
    A diminutive perinate European Enantiornithes reveals an asynchronous ossification pattern in early birds2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 937Article in journal (Refereed)
    Abstract [en]

    Fossils of juvenile Mesozoic birds provide insight into the early evolution of avian development, however such fossils are rare. The analysis of the ossification sequence in these early-branching birds has the potential to address important questions about their comparative developmental biology and to help understand their morphological evolution and ecological differentiation. Here we report on an early juvenile enantiornithine specimen from the Early Cretaceous of Europe, which sheds new light on the osteogenesis in this most species-rich clade of Mesozoic birds. Consisting of a nearly complete skeleton, it is amongst the smallest known Mesozoic avian fossils representing post-hatching stages of development. Comparisons between this new specimen and other known early juvenile enantiornithines support a clade-wide asynchronous pattern of osteogenesis in the sternum and the vertebral column, and strongly indicate that the hatchlings of these phylogenetically basal birds varied greatly in size and tempo of skeletal maturation.

  • 29.
    Looy, Cindy V.
    et al.
    Univ Calif Berkeley, Dept Integrat Biol, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Museum Paleontol, Berkeley, CA 94720 USA..
    Ranks, Stephanie L.
    Univ Calif Berkeley, Dept Integrat Biol, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Museum Paleontol, Berkeley, CA 94720 USA..
    Chaney, Dan S.
    Smithsonian Inst, NMNH, Dept Paleobiol, Washington, DC 20560 USA..
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Steyer, Jean-Sebastien
    UPMC, Ctr Rech Paleobiodivers & Paleoenvironnements, MNHN, UMR 7207,CNRS, CP 38,8 Rue Buffon, F-75005 Paris, France..
    Smith, Roger M. H.
    Iziko South African Museum, Karoo Palaeontol, ZA-8000 Cape Town, South Africa.;Univ Witwatersrand, Evolutionary Studies Inst, 1 Jan Smuts Ave, ZA-2000 Johannesburg, South Africa..
    Sidor, Christian A.
    Univ Washington, Burke Museum, Seattle, WA 98195 USA.;Univ Washington, Dept Biol, Seattle, WA 98195 USA..
    Myers, Timothy S.
    So Methodist Univ, Huffington Dept Earth Sci, Dallas, TX 75275 USA..
    Ide, Oumarou
    Inst Rech Sci Humaines, Niamey, Niger..
    Tabor, Neil J.
    So Methodist Univ, Huffington Dept Earth Sci, Dallas, TX 75275 USA..
    Biological and physical evidence for extreme seasonality in central Permian Pangea2016In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 451, p. 210-226Article in journal (Refereed)
    Abstract [en]

    Climate models indicate increased desertification in the continental interior of Pangea during the Permian, which would have affected the composition of the flora and fauna. We present a multi-proxy paleoenvironmental reconstruction of a terrestrial ecosystem in central Pangea of Lopingian age. The reconstruction is based on biological and physical data from the Moradi Formation, located in the Tim Mersoi sub-Basin, northern Niger. Paleosols and sedimentological evidence indicate that the prevailing climate was semi-arid to very arid with marked intervals of high water availability. Carbon stable isotope data from organic matter and paleosols suggest that both the soil productivity and actual evapotranspiration were very low, corresponding to arid conditions. Histological analysis of pareiasaur bones shows evidence of active metabolism and reveals distinct growth marks. These interruptions of bone formation are indicative of growth rhythms, and are considered as markers for contrasting seasonality orepisodic climate events. The macrofossil floras have low diversity and represent gymnosperm dominated woodlands. Most notable are ovuliferous dwarf shoots of voltzian conifers, and a 25-m long tree trunk with irregularly positioned branch scars. The combined biological and physical evidence suggests that the Moradi Formation was deposited under a generally arid climate with recurring periods of water abundance, allowing for a well-established ground water-dependent ecosystem. With respect to its environment, this system is comparable with modern ecosystems such as the southern African Namib Desert and the Lake Eyre Basin in Australia, which are discussed as modern analogues.

  • 30. Mondejar-Fernandez, Jorge
    et al.
    Clement, Gael
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    New insights into the scales of the Devonian tetrapod Tulerpeton curtum Lebedev, 19842014In: Journal of Vertebrate Paleontology, ISSN 0272-4634, E-ISSN 1937-2809, Vol. 34, no 6, p. 1454-1459Article in journal (Refereed)
  • 31.
    Murer, Fredrik K.
    et al.
    Norwegian Univ Sci & Technol, Dept Phys, Hgsk Ringen 5, N-7491 Trondheim, Norway.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. UPMC, CNRS, Sorbonne Univ, CR2P,MNHN, 57 Rue Cuvier,CP38, F-75005 Paris, France;ESRF, 71 Ave Martyrs, F-38000 Grenoble, France.
    Alvarez-Murga, Michelle
    ESRF, 71 Ave Martyrs, F-38000 Grenoble, France.
    Di Michiel, Marco
    ESRF, 71 Ave Martyrs, F-38000 Grenoble, France.
    Pfeiffer, Franz
    Tech Univ Munich, Lehrstuhl Biomed Phys, Dept Phys, D-85748 Garching, Germany;Tech Univ Munich, Inst Med Tech, D-85748 Garching, Germany;Tech Univ Munich, Klinikum Rechts Isar, Dept Diagnost & Intervent Radiol, D-81675 Munich, Germany.
    Bech, Martin
    Lund Univ, Dept Med Radiat Phys, Clin Sci, S-22185 Lund, Sweden.
    Breiby, Dag W.
    Univ South Eastern Norway, Dept Microsyst, N-3184 Borre, Norway;Norwegian Univ Sci & Technol, Dept Phys, Hgsk Ringen 5, N-7491 Trondheim, Norway.
    3D Maps of Mineral Composition and Hydroxyapatite Orientation in Fossil Bone Samples Obtained by X-ray Diffraction Computed Tomography2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 10052Article in journal (Refereed)
    Abstract [en]

    Whether hydroxyapatite (HA) orientation in fossilised bone samples can be non-destructively retrieved and used to determine the arrangement of the bone matrix and the location of muscle attachments (entheses), is a question of high relevance to palaeontology, as it facilitates a detailed understanding of the (micro-)anatomy of extinct species with no damage to the precious fossil specimens. Here, we report studies of two fossil bone samples, specifically the tibia of a 300-million-year-old tetrapod, Discosauriscus austriacus, and the humerus of a 370-million-year-old lobe-finned fish, Eusthenopteron foordi, using XRD-CT - a combination of X-ray diffraction (XRD) and computed tomography (CT). Reconstructed 3D images showing the spatial mineral distributions and the local orientation of HA were obtained. For Discosauriscus austriacus, details of the muscle attachments could be discerned. For Eusthenopteron foordi, the gross details of the preferred orientation of HA were deduced using three tomographic datasets obtained with orthogonally oriented rotation axes. For both samples, the HA in the bone matrix exhibited preferred orientation, with the unit cell c-axis of the HA crystallites tending to be parallel with the bone surface. In summary, we have demonstrated that XRD-CT combined with an intuitive reconstruction procedure is becoming a powerful tool for studying palaeontological samples.

  • 32. Pierce, Stephanie E.
    et al.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Hutchinson, John R.
    Molnar, Julia L.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Tafforeau, Paul
    Clack, Jennifer A.
    Vertebral architecture in the earliest stem tetrapods2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 494, no 7436, p. 226-229Article in journal (Refereed)
    Abstract [en]

    The construction of the vertebral column has been used as a key anatomical character in defining and diagnosing early tetrapod groups(1). Rhachitomous vertebrae(2)-in which there is a dorsally placed neural arch and spine, an anteroventially placed intercentrum and paired, posterodorsally placed pleurocentra have long been considered the ancestral morphology for tetrapods(1,3-6). Nonetheless, very little is known about vertebral anatomy in the earliest stem tetrapods, because most specimens remain trapped in surrounding matrix, obscuring Important anatomical features(7-9). Here we describe the three-dimensional vertebral architecture of the Late Devonian stem tetrapod Ichthyostega using propagation phase-contrast X-ray synchrotron. microtomography. Our scans reveal a diverse array of new morphological, and associated developmental and functional, characteristics, including a possible posterior-to-anterior vertebral ossification sequence and the first evolutionary appearance of ossified sternal elements. One of the most intriguing features relates to the positional relationships between the vertebral elements, with the pleurocentra being unexpectedly sutured or fused to the intercentra that directly succeed them, indicating a 'reverse' rhachitomous design(10). Comparison of Ichthyostega with two other stem tetrapods, Acanthostegi and Pederpess, shows that reverse rhachitomous vertebrae may be the ancestral condition for limbed vertebrates. This study fundamentally revises our current understanding' of vertebral column evolution in the earliest tetrapods and raises questions about the presumed vertebral architecture of tetrapodomorph fish(12,13) and later, more crownward, tetrapods.

  • 33.
    Qu, Qingming
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Tafforeau, Paul
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Scales and Tooth Whorls of Ancient Fishes Challenge Distinction between External and Oral 'Teeth'2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 8, p. e71890-Article in journal (Refereed)
    Abstract [en]

    The debate about the origin of the vertebrate dentition has been given fresh fuel by new fossil discoveries and developmental studies of extant animals. Odontodes (teeth or tooth-like structures) can be found in two distinct regions, the 'internal' oropharyngeal cavity and the 'external' skin. A recent hypothesis argues that regularly patterned odontodes is a specific oropharyngeal feature, whereas odontodes in the external skeleton lack this organization. However, this argument relies on the skeletal system of modern chondrichthyans (sharks and their relatives), which differ from other gnathostome (jawed vertebrate) groups in not having dermal bones associated with the odontodes. Their external skeleton is also composed of monoodontode 'placoid scales', whereas the scales of most early fossil gnathostomes are polyodontode, i.e. constructed from several odontodes on a shared bony base. Propagation phase contrast X-ray Synchrotron microtomography (PPC-SRmCT) is used to study the polyodontode scales of the early bony fish Andreolepis hedei. The odontodes constructing a single scale are reconstructed in 3D, and a linear and regular growth mechanism similar to that in a gnathostome dentition is confirmed, together with a second, gap-filling growth mechanism. Acanthodian tooth whorls are described, which show that ossification of the whorl base preceded and probably patterned the development of the dental lamina, in contrast to the condition in sharks where the dental lamina develops early and patterns the dentition. The new findings reveal, for the first time, how polyodontode scales grow in 3D in an extinct bony fish. They show that dentition-like odontode patterning occurs on scales and that the primary patterning unit of a tooth whorl may be the bony base rather than the odontodes it carries. These results contradict the hypothesis that oropharyngeal and external odontode skeletons are fundamentally separate and suggest that the importance of dermal bone interactions to odontode patterning has been underestimated.

  • 34.
    Qu, Qingming
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, 71 Ave Martyrs, F-38043 Grenoble 09, France.
    Zhu, Min
    Chinese Acad Sci, Inst Vertebrate Paleontol & Paleoanthropol, Key Lab Vertebrate Evolut & Human Origins, Xiwaidajie 142, Beijing 100044, Peoples R China.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per E
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    The origin of novel features by changes in developmental mechanisms: ontogeny and three-dimensional microanatomy of polyodontode scales of two early osteichthyans2017In: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 92, no 2, p. 1189-1212Article in journal (Refereed)
    Abstract [en]

    Recent advances in synchrotron imaging allow us to study the three-dimensional (3D) histology of vertebrate fossils, including microfossils (e.g. teeth and scales) of early jawed vertebrates. These microfossils can often be scanned at submicron resolution (<1 µm) because of their small size. The resulting voxel (3D pixel) stacks can be processed into virtual thin sections revealing almost every internal detail of the samples, comparable to traditional thin sections. In addition, 3D models of the internal microanatomical structures, such as embedded odontodes and vasculature, can be assembled and examined in situ. Scales of two early osteichthyans, Psarolepis romeri from the Early Devonian of China and Andreolepis hedei from the Late Silurian of Sweden, were scanned using propagation phase-contrast synchrotron X-ray microtomography (PPC-SRµCT), and 3D models of internal canal systems and buried odontodes were created from the scans. Based on these new data, we review the evolutionary origin of cosmine and its associated pore-canal system, which has been long recognized as a synapomorphy of sarcopterygians. The first odontode that appeared during growth shows almost identical morphology in the two scales, but the second odontode of the Psarolepis scale shows a distinctive morphology with several pores on the surface. It is suggested that a shift from ridge-like odontode to pore-bearing odontode was the key step in the origin of cosmine, which was then elaborated further in more-derived sarcopterygians. We perform a detailed comparison between the two scales and propose a primary homology framework to generate microanatomical characters, which can be used in the phylogenetic analysis of early osteichthyans when more 3D data become available. Our results highlight the importance of 3D data for the study of histology and ontogeny of the dermal skeleton of early jawed vertebrates, especially scales of the polyodontode type. The traditional microvertebrate collection is not only useful for biostratigraphic studies, but also preserves invaluable biological information about the growth of vertebrate hard tissues. Today, we are only beginning to understand the biological meaning of the new 3D data. The increasing availability of such data will enable, and indeed require, a complete revision of traditional palaeohistological studies on early vertebrates.

  • 35.
    Qu, Qingming
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Zhu, Min
    Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Tafforeau, Paul
    European Synchrotron Radiation Facility.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The origin of novel features by changes in developmental mechanisms: a 3D virtual paleohistology study on polyodontode scales of primitive osteichthyans2015Manuscript (preprint) (Other academic)
  • 36.
    Ryll, Bettina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Haitina, Tatjana
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Tafforeau, Paul
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The genome of Callorhinchus and the fossil record: a new perspective on SCPP gene evolution in gnathostomes2014In: Evolution & Development, ISSN 1520-541X, E-ISSN 1525-142X, Vol. 16, no 3, p. 123-124Article in journal (Other academic)
  • 37.
    Sanchez, Sophie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Trinajstic, Katherine M.
    Mirone, Alessandro
    Tafforeau, Paul
    Three-Dimensional Synchrotron Virtual Paleohistology: A New Insight into the World of Fossil Bone Microstructures2012In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 18, no 5, p. 1095-1105Article in journal (Refereed)
    Abstract [en]

    The recent developments of phase-contrast synchrotron imaging techniques have been of great interest for paleontologists, providing three-dimensional (3D) tomographic images of anatomical structures, thereby leading to new paleobiological insights and the discovery of new species. However, until now, it has not been used on features smaller than 57 mu m voxel size in fossil bones. Because much information is contained within the 3D histological architecture of bone, including an ontogenetic record, crucial for understanding the paleobiology of fossil species, the application of phase-contrast synchrotron tomography to bone at higher resolutions is potentially of great interest. Here we use this technique to provide new 3D insights into the submicron-scale histology of fossil and recent bones, based on the development of new pink-beam configurations, data acquisition strategies, and improved processing tools. Not only do the scans reveal by nondestructive means all of the major features of the histology at a resolution comparable to that of optical microscopy, they provide 3D information that cannot be obtained by any other method.

  • 38.
    Sanchez, Sophie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    de Ploeg, Gael
    Clément, Gael
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    A new tool for determining degrees of mineralization in fossil amphibian skeletons: The example of the Late Palaeozoic branchiosaurid Apateon from the Autun Basin, France2010In: Comptes rendus. Palevol, ISSN 1631-0683, E-ISSN 1777-571X, Vol. 9, no 6-7, p. 311-317Article in journal (Refereed)
    Abstract [en]

    Studying ontogenetic features of fossil tetrapods is of major interest for investigating the adaptive strategies of early tetrapods to their palaeoenvironments. To determine the degree of calcification of skeletal elements, biologists have until now relied on X-ray radiographs of organisms or isolated bones, or on thin sections. An X-ray tomographic scan of Apateon, a Carboniferous - Permian branchiosaurid from the Autun Basin, France, reveals distinct density properties related to different mineralized tissues (calcified cartilage versus bone). The rendering of Apateon as a "test individual" provides a 3D map of the degrees of ossification of the axial and cranial elements. The combination of these anatomical observations with histological information from classical thin sections made in limb bones of several other specimens of the same locality allows the detailed determination of their ontogenetic stage. A comparison with the well-known specimens of the Saar-Nahe Basin, Germany, makes it possible to investigate the influence of different palaeoenvironments on ontogenetic features.

  • 39.
    Sanchez, Sophie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Dupret, Vincent
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ryll, Bettina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Trinajstic, Kate
    Curtin University, Western Australia.
    Wretman, Lovisa
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Zylberberg, Louise
    Université Pierre et Marie Curie, UPMC, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Fossil bone histology revealed in 3D thanks to the synchrotron light: palaeobiological implications2011Conference paper (Refereed)
  • 40.
    Sanchez, Sophie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Dupret, Vincent
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ryll, Bettina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Trinajstic, Kate
    Curti University, Western Australia.
    Wretman, Lovisa
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Zylberberg, Louise
    Université Pierre et Marie Curie, UPMC, Paris, France.
    Tafforeau, Paul
    European Synchrotron Radiation Facility, Grenoble, France.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Synchrotron virtual palaeohistology: a new tool for studying the evolution of bone microstructures in 3D2011Conference paper (Refereed)
  • 41.
    Sanchez, Sophie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Dupret, Vincent
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
    Tafforeau, Paul
    Trinajstic, Katherine M.
    Ryll, Bettina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Gouttenoire, Pierre-Jean
    Wretman, Lovisa
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Zylberberg, Louise
    Peyrin, Francoise
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    3D Microstructural Architecture of Muscle Attachments in Extant and Fossil Vertebrates Revealed by Synchrotron Microtomography2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 2, p. e56992-Article in journal (Refereed)
    Abstract [en]

    Background: Firm attachments binding muscles to skeleton are crucial mechanical components of the vertebrate body. These attachments (entheses) are complex three-dimensional structures, containing distinctive arrangements of cells and fibre systems embedded in the bone, which can be modified during ontogeny. Until recently it has only been possible to obtain 2D surface and thin section images of entheses, leaving their 3D histology largely unstudied except by extrapolation from 2D data. Entheses are frequently preserved in fossil bones, but sectioning is inappropriate for rare or unique fossil material.

    Methodology/Principal Findings: Here we present the first non-destructive 3D investigation, by propagation phase contrast synchrotron microtomography (PPC-SR mu CT), of enthesis histology in extant and fossil vertebrates. We are able to identify entheses in the humerus of the salamander Desmognathus from the organization of bone-cell lacunae and extrinsic fibres. Statistical analysis of the lacunae differentiates types of attachments, and the orientation of the fibres, reflect the approximate alignment of the muscle. Similar histological structures, including ontogenetically related pattern changes, are perfectly preserved in two 380 million year old fossil vertebrates, the placoderm Compagopiscis croucheri and the sarcopterygian fish Eusthenopteron foordi.

    Conclusions/Significance: We are able to determine the position of entheses in fossil vertebrates, the approximate orientation of the attached muscles, and aspects of their ontogenetic histories, from PPC-SRmCT data. Sub-micron microtomography thus provides a powerful tool for studying the structure, development, evolution and palaeobiology of muscle attachments.

  • 42.
    Sanchez, Sophie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Fernandez, Vincent
    Pierce, Stephanie E.
    Tafforeau, Paul
    Homogenization of sample absorption for the imaging of large and dense fossils with synchrotron microtomography2013In: Nature Protocols, ISSN 1754-2189, E-ISSN 1750-2799, Vol. 8, no 9, p. 1708-1717Article in journal (Refereed)
    Abstract [en]

    Propagation phase-contrast synchrotron radiation microtomography (PPC-SR mu CT) has proved to be very successful for examining fossils. Because fossils range widely in taphonomic preservation, size, shape and density, X-ray computed tomography protocols are constantly being developed and refined. Here we present a 1-h procedure that combines a filtered high-energy polychromatic beam with long-distance PPC-SR mu CT (sample to detector: 4-16 m) and an attenuation protocol normalizing the absorption profile (tested on 13-cm-thick and 5.242 g cm(-3) locally dense samples but applicable to 20-cm-thick samples). This approach provides high-quality imaging results, which show marked improvement relative to results from images obtained without the attenuation protocol in apparent transmission, contrast and signal-to-noise ratio. The attenuation protocol involves immersing samples in a tube filled with aluminum or glass balls in association with a U-shaped aluminum profiler. This technique therefore provides access to a larger dynamic range of the detector used for tomographic reconstruction. This protocol homogenizes beam-hardening artifacts, thereby rendering it effective for use with conventional mu CT scanners.

  • 43.
    Sanchez, Sophie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Schoch, R. R.
    Bone Histology Reveals a High Environmental and Metabolic Plasticity as a Successful Evolutionary Strategy in a Long-Lived Homeostatic Triassic Temnospondyl2013In: Evolutionary biology, ISSN 0071-3260, E-ISSN 1934-2845, Vol. 40, no 4, p. 627-647Article in journal (Refereed)
    Abstract [en]

    Evolutionary stasis (long-term stability of morphology in an evolving lineage) is a pattern for which explanations are usually elusive. The Triassic tetrapod Gerrothorax pulcherrimus, a gill-bearing temnospondyl, survived for 35 million years in the Germanic Basin of Central Europe persisting throughout the dinosaur-dominated Late Triassic period. This evolutionary stasis coincides with the occurrence of this species in a wide range of habitats and environmental conditions. By the combination of palaeoecological and palaeohistological analyses, we found great ecological flexibility in G. pulcherrimus and present substantial evidence of developmental and metabolic plasticity despite the morphological stasis. We conclude that G. pulcherrimus could show the capacity to settle in water bodies too harsh or unpredictable for most other tetrapods. This would have been made possible by a unique life history strategy that involved a wide reaction norm, permitting adjustment to fluctuating conditions such as salinity and level of nutrients. Growth rate, duration of juvenile period, age at maturity, and life span were all subject to broad variation within specimens of G. pulcherrimus in one single lake and in between different lakes. In addition to providing a better understanding of fossil ecosystems, this study shows the potential of such a methodology to encourage palaeobiologists and evolutionary biologists to consider the mechanisms of variation in extant and fossil organisms by using a similar time-scope reference.

  • 44.
    Sanchez, Sophie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Tafforeau, P.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The humerus of Eusthenopteron: a puzzling organization presaging the establishment of tetrapod limb bone marrow2014In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 281, no 1782, p. 20140299-Article in journal (Refereed)
    Abstract [en]

    Because of its close relationship to tetrapods, Eusthenopteron is an important taxon for understanding the establishment of the tetrapod body plan. Notably, it is one of the earliest sarcopterygians in which the humerus of the pectoral fin skeleton is preserved. The microanatomical and histological organization of this humerus provides important data for understanding the evolutionary steps that built up the distinctive architecture of tetrapod limb bones. Previous histological studies showed that Eusthenopteron's long-bone organization was established through typical tetrapod ossification modalities. Based on a threedimensional reconstruction of the inner microstructure of Eusthenopteron's humerus, obtained from propagation phase-contrast X-ray synchrotron microtomography, we are now able to show that, despite ossification mechanisms and growth patterns similar to those of tetrapods, it also retains plesiomorphic characters such as a large medullary cavity, partly resulting from the perichondral ossification around a large cartilaginous bud as in actinopterygians. It also exhibits a distinctive tubular organization of bone-marrow processes. The connection between these processes and epiphyseal structures highlights their close functional relationship, suggesting that either bone marrow played a crucial role in the long-bone elongation processes or that trabecular bone resulting from the erosion of hypertrophied cartilage created a microenvironment for haematopoietic stem cell niches.

  • 45. Steyer, J. -Sebastien
    et al.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Debriette, Pierre J.
    Valli, Andrea M. F.
    Escuille, Francois
    Pohl, Burkhard
    Dechambre, Roger-Paul
    Vacant, Renaud
    Spence, Christopher
    de Ploeg, Gael
    A new vertebrate Lagerstatte from the Lower Permian of France (Franchesse, Massif Central): palaeoenvironmental implications for the Bourbon-l'Archambault basin2012In: Bulletin de la Société Géologique de France, ISSN 0037-9409, E-ISSN 1777-5817, Vol. 183, no 6, p. 509-515Article in journal (Refereed)
    Abstract [en]

    A new vertebrate locality from the Lower Permian (Cisuralian) of the Bourbon-l'Archambault basin (Massif Central, France) is reported and its associated flora and fauna preliminarily described. This locality corresponds to a mass mortality assemblage deposited in an aquatic environment. Interestingly, it has yielded hundreds of exceptionally well preserved seymouriamorph specimens, all referred to Discosauriscus austriacus. This exquisite assemblage corresponds to the first seymouriamorph Lagerstatte and the first record of D. austriacus outside the Boskovice basin in Czechia. It enlarges the geographical distribution of the species during the Early Permian, and has new palaeoenvironmental implications regarding the Palaeozoic Bourbon-l'Archambault basin.

  • 46. Trinajstic, Kate
    et al.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Dupret, Vincent
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Tafforeau, Paul
    Long, John
    Young, Gavin
    Senden, Tim
    Boisvert, Catherine
    Power, Nicola
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Fossil Musculature of the Most Primitive Jawed Vertebrates2013In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 341, no 6142, p. 160-164Article in journal (Refereed)
    Abstract [en]

    The transition from jawless to jawed vertebrates (gnathostomes) resulted in the reconfiguration of the muscles and skeleton of the head, including the creation of a separate shoulder girdle with distinct neck muscles. We describe here the only known examples of preserved musculature from placoderms (extinct armored fishes), the phylogenetically most basal jawed vertebrates. Placoderms possess a regionalized muscular anatomy that differs radically from the musculature of extant sharks, which is often viewed as primitive for gnathostomes. The placoderm data suggest that neck musculature evolved together with a dermal joint between skull and shoulder girdle, not as part of a broadly flexible neck as in sharks, and that transverse abdominal muscles are an innovation of gnathostomes rather than of tetrapods.

  • 47.
    Voeten, Dennis F. A. E.
    et al.
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS-40220, F-38043 Grenoble, France.;Palacky Univ, Dept Zool, 17 Listopadu 50, Olomouc 77146, Czech Republic.;Palacky Univ, Lab Ornithol, 17 Listopadu 50, Olomouc 77146, Czech Republic..
    Cubo, Jorge
    Sorbonne Univ, CNRS INSU, Inst Sci Terre Paris, ISTeP UMR 7193, F-75005 Paris, France..
    de Margerie, Emmanuel
    Univ Rennes 1, Univ Caen Normandie, CNRS, Lab Ethol Anim & Humaine, 263 Ave Gen Leclerc, F-35042 Rennes, France..
    Roeper, Martin
    Burgermeister Muller Museum, Bahnhofstr 8, D-91807 Solnhofen, Germany.;Bayerische Staatssammlung Palaontol & Geol, Richard Wagner Str 10, D-80333 Munich, Germany..
    Beyrand, Vincent
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS-40220, F-38043 Grenoble, France.;Palacky Univ, Dept Zool, 17 Listopadu 50, Olomouc 77146, Czech Republic.;Palacky Univ, Lab Ornithol, 17 Listopadu 50, Olomouc 77146, Czech Republic..
    Bures, Stanislav
    Palacky Univ, Dept Zool, 17 Listopadu 50, Olomouc 77146, Czech Republic.;Palacky Univ, Lab Ornithol, 17 Listopadu 50, Olomouc 77146, Czech Republic..
    Tafforeau, Paul
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS-40220, F-38043 Grenoble, France..
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, 71 Ave Martyrs,CS-40220, F-38043 Grenoble, France.
    Wing bone geometry reveals active flight in Archaeopteryx2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 923Article in journal (Refereed)
    Abstract [en]

    Archaeopteryx is an iconic fossil taxon with feathered wings from the Late Jurassic of Germany that occupies a crucial position for understanding the early evolution of avian flight. After over 150 years of study, its mosaic anatomy unifying characters of both non-flying dinosaurs and flying birds has remained challenging to interpret in a locomotory context. Here, we compare new data from three Archaeopteryx specimens obtained through phase-contrast synchrotron microtomography to a representative sample of archosaurs employing a diverse array of locomotory strategies. Our analyses reveal that the architecture of Archaeopteryx's wing bones consistently exhibits a combination of cross-sectional geometric properties uniquely shared with volant birds, particularly those occasionally utilising short-distance flapping. We therefore interpret that Archaeopteryx actively employed wing flapping to take to the air through a more anterodorsally posteroventrally oriented flight stroke than used by modern birds. This unexpected outcome implies that avian powered flight must have originated before the latest Jurassic.

  • 48.
    Xie, Meng
    et al.
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm.
    Gol'din, Pavel
    Stockholm Univ, Stockholm.
    Estsfa, Jordi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
    Li, Lei
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm.
    Arregui, Irene Linares
    KTH, Dept Solid Mech, Stockholm.
    Gasser, Christian
    KTH, Dept Solid Mech, Stockholm.
    Medvedeva, Ekaterina
    Sechenov Med Univ, Moscow.
    Svetlana, Kotova
    Sechenov Med Univ, Moscow.
    Timashev, Peter
    Sechenov Med Univ, Moscow.
    Adameyko, Igor
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm.
    Eriksson, Anders
    KTH, Dept Mech, Stockholm.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Chagin, Andrei
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm.
    Evolutional Separation of Epiphyseal and Articular Cartilage is a Bone Adaptation to Terrestrial Growth.2017In: Journal of Bone and Mineral Research, ISSN 0884-0431, E-ISSN 1523-4681, Vol. 32, no S1, p. S328-S328, article id Meeting Abstract: MO0490Article in journal (Other academic)
1 - 48 of 48
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