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Blom, Henning
Publications (10 of 71) Show all publications
Chen, D. L., Blom, H., Sanchez, S., Tafforeau, P., Märss, T. & Ahlberg, P. E. (2017). Development of cyclic shedding teeth from semi-shedding teeth: the inner dental arcade of the stem osteichthyan Lophosteus . Royal Society Open Science, 4(5), Article ID 161084.
Open this publication in new window or tab >>Development of cyclic shedding teeth from semi-shedding teeth: the inner dental arcade of the stem osteichthyan Lophosteus 
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2017 (English)In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 4, no 5, article id 161084Article in journal (Refereed) Published
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. 

Place, publisher, year, edition, pages
ROYAL SOC, 2017
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-315882 (URN)10.1098/rsos.161084 (DOI)000402541800020 ()28573003 (PubMedID)
Available from: 2017-02-22 Created: 2017-02-22 Last updated: 2017-08-02Bibliographically approved
Qu, Q., Sanchez, S., Zhu, M., Blom, H. & Ahlberg, P. E. (2017). The origin of novel features by changes in developmental mechanisms: ontogeny and three-dimensional microanatomy of polyodontode scales of two early osteichthyans. Biological Reviews, 92(2), 1189-1212
Open this publication in new window or tab >>The origin of novel features by changes in developmental mechanisms: ontogeny and three-dimensional microanatomy of polyodontode scales of two early osteichthyans
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2017 (English)In: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 92, no 2, p. 1189-1212Article in journal (Refereed) Published
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.

National Category
Evolutionary Biology Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-298047 (URN)10.1111/brv.12277 (DOI)000398567200032 ()27194072 (PubMedID)
Funder
EU, European Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2016-06-29 Created: 2016-06-29 Last updated: 2017-05-04Bibliographically approved
Bremer, O., Niedźwiedzki, G., Blom, H., Dec, M. & Kozłowski, W. (2017). Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland. In: : . Paper presented at 14th International Symposium on Early and Lower Vertebrates in the Holy Cross Mountains, Poland, July 3-8 2017.
Open this publication in new window or tab >>Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland
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2017 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-328147 (URN)
Conference
14th International Symposium on Early and Lower Vertebrates in the Holy Cross Mountains, Poland, July 3-8 2017
Available from: 2017-08-18 Created: 2017-08-18 Last updated: 2017-11-27Bibliographically approved
Zaton, M., Niedzwiedzki, G., Blom, H. & Kear, B. P. (2016). Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction. Scientific Reports, 6, Article ID 36345.
Open this publication in new window or tab >>Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction
2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 36345Article in journal (Refereed) Published
Abstract [en]

The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic. Its aftermath was characterized by harsh marine conditions incorporating volcanically induced oceanic warming, widespread anoxia and acidification. Bio-productivity accordingly experienced marked fluctuations. In particular, low palaeolatitude hard substrate communities from shallow seas fringing Western Pangaea and the Tethyan Realm were extremely impoverished, being dominated by monogeneric colonies of filter-feeding microconchid tubeworms. Here we present the first equivalent field data for Boreal hard substrate assemblages from the earliest Triassic (Induan) of East Greenland. This region bordered a discrete bio-realm situated at mid-high palaeolatitude (> 30 degrees N). Nevertheless, hard substrate biotas were compositionally identical to those from elsewhere, with microconchids encrusting Claraia bivalves and algal buildups on the sea floor. Biostratigraphical correlation further shows that Boreal microconchids underwent progressive tube modification and unique taxic diversification concordant with changing habitats over time. We interpret this as a post-extinction recovery and adaptive radiation sequence that mirrored coeval subequatorial faunas, and thus confirms hard substrate ecosystem depletion as a hallmark of the earliest Triassic interval globally.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-309809 (URN)10.1038/srep36345 (DOI)000387314500001 ()27821855 (PubMedID)
Funder
Swedish Polar Research Secretariat
Available from: 2016-12-14 Created: 2016-12-07 Last updated: 2017-11-29Bibliographically approved
Hairapetian, V., Blom, H. & Turner, S. (2016). Early Frasnian thelodont scales from central Iran and their implications for turiniid taxonomy, systematics and distribution. Journal of Vertebrate Paleontology, 36(3), Article ID e1100632.
Open this publication in new window or tab >>Early Frasnian thelodont scales from central Iran and their implications for turiniid taxonomy, systematics and distribution
2016 (English)In: Journal of Vertebrate Paleontology, ISSN 0272-4634, E-ISSN 1937-2809, Vol. 36, no 3, article id e1100632Article in journal (Refereed) Published
Abstract [en]

We describe isolated shark teeth collected in levels of the Calafate Formation (Maastrichtian, Late Cretaceous) on the southeast coast of Argentino Lake, Calafate City, Santa Cruz Province, Argentina. The teeth belong to the hexanchiform Notidanodon dentatus, a new species of the squaliform Protosqualus, and an indeterminate species of the echinorhiniform genus Echinorhinus. The record of Notidanodon constitutes the first in South America. The report of Notidanodon associated with plesiosaur remains is in accordance with previous records from around the world. Protosqualus argentinensis, nov. sp., which is the first record of the genus in South America, is characterized by having teeth with a apicobasally tall root and serrated cutting edges, among other features.Echinorhinus sp. constitutes one of the oldest records of this genus on the continent and one of the few Mesozoic records worldwide. This shark association is clearly distinct from coeval selachian faunas from northern Patagonia, which exhibit clear Tethyan influences. Instead, it shows some similarities to other high-latitude selachian faunas, including Australia, New Zealand, and Antarctica. It is possible that the Cretaceous selachian assemblages of Patagonia may be separated into two different associations: northern Patagonian faunas are related to more temperate associations of lower paleolatitudes, whereas those of southern Patagonia are closer to other southern localities.

National Category
Natural Sciences Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-282430 (URN)10.1080/02724634.2016.1100632 (DOI)000374557800011 ()
Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2017-11-30Bibliographically approved
Wretman, L., Blom, H. & Kear, B. P. (2016). Resolution of the Early Jurassic actinopterygian fish Pachycormus and a dispersal hypothesis for Pachycormiformes. Journal of Vertebrate Paleontology, 36(5), Article ID e1206022.
Open this publication in new window or tab >>Resolution of the Early Jurassic actinopterygian fish Pachycormus and a dispersal hypothesis for Pachycormiformes
2016 (English)In: Journal of Vertebrate Paleontology, ISSN 0272-4634, E-ISSN 1937-2809, Vol. 36, no 5, article id e1206022Article in journal (Refereed) Published
Abstract [en]

The Early Jurassic (Toarcian) actinopterygian Pachycormus is a basal taxon within Pachycormiformes, a Mesozoic marine neopterygian radiation that evolved an extreme ecomorph divergence between hyperspecialized billfish-like' macrocarnivores and gigantic suspension feeders, including the largest fish of all time. Current phylogenies place Pachycormus as an early member of the suspension-feeding lineage; however, species disparity renders character states uncertain and potential exists for considerable intraspecific variability. Given its importance for resolution of pachycormiform phylogenetic topology, we comprehensively reassessed Pachycormus fossils housed in collections across Europe and found that the proportional traits traditionally used to discriminate between species are actually consistent with an ontogenetic size morphocline. Our cladistic analyses further show that the monotypic senior synonym, Pachycormus macropterus, is a wildcard that manifests a mosaic of transitional states. This has significant implications for hypothesized Toarcian marine vertebrate provincialism because P. macropterus had a ubiquitous Boreal Tethyan distribution. Moreover, our tree-based palaeobiogeographical optimizations infer that the western Tethyan region was a pachycormiform dissemination center, with global dispersals occurring through transoceanic migration and invasion of epeiric basins.Citation for this article: Wretman, L., H. Blom, and B. P. Kear. 2016. Resolution of the Early Jurassic actinopterygian fish Pachycormus and a dispersal hypothesis for Pachycormiformes. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1206022.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-305928 (URN)10.1080/02724634.2016.1206022 (DOI)000384029300020 ()
Available from: 2016-11-14 Created: 2016-10-24 Last updated: 2017-11-29Bibliographically approved
Chen, D., Blom, H., Sanchez, S., Tafforeau, P. & Ahlberg, P. (2016). The stem osteichthyan Andreolepis and the origin of tooth replacement. Nature, 539(7628), 237-+
Open this publication in new window or tab >>The stem osteichthyan Andreolepis and the origin of tooth replacement
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2016 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 539, no 7628, p. 237-+Article in journal (Refereed) Published
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.

National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-310754 (URN)10.1038/nature19812 (DOI)000387318500034 ()27750278 (PubMedID)
Funder
EU, European Research Council, 233111Knut and Alice Wallenberg Foundation
Available from: 2016-12-20 Created: 2016-12-19 Last updated: 2017-11-29Bibliographically approved
Jerve, A., Qu, Q., Sanchez, S., Blom, H. & Ahlberg, P. E. (2016). Three-dimensional paleohistology of the scale and median fin spine of Lophosteus superbus (Pander 1856). PeerJ, 4, Article ID e2521.
Open this publication in new window or tab >>Three-dimensional paleohistology of the scale and median fin spine of Lophosteus superbus (Pander 1856)
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2016 (English)In: PeerJ, ISSN 2167-8359, E-ISSN 2167-8359, Vol. 4, article id e2521Article in journal (Refereed) Published
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.

National Category
Natural Sciences
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
urn:nbn:se:uu:diva-282529 (URN)10.7717/peerj.2521 (DOI)000387169900002 ()27833794 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationEU, European Research Council, 233111
Available from: 2016-04-21 Created: 2016-04-05 Last updated: 2017-11-30Bibliographically approved
Bremer, O. & Blom, H. (2015). An updated stratigraphic and environmental framework for the distribution of Silurian vertebrates on Gotland. Estonian journal of earth sciences, 64(1), 13-18
Open this publication in new window or tab >>An updated stratigraphic and environmental framework for the distribution of Silurian vertebrates on Gotland
2015 (English)In: Estonian journal of earth sciences, ISSN 1736-4728, E-ISSN 1736-7557, Vol. 64, no 1, p. 13-18Article in journal (Refereed) Published
Keyword
vertebrate distribution, stratigraphy, facies, Silurian events, Gotland, Sweden
National Category
Developmental Biology Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-251824 (URN)10.3176/earth.2015.03 (DOI)000351327700004 ()
Available from: 2015-04-27 Created: 2015-04-24 Last updated: 2017-08-21
Fadel, A., Zigaite, Z., Blom, H., Perez-Huerta, A., Jeffries, T., Maersse, T. & Ahlberg, P. E. (2015). Palaeoenvironmental signatures revealed from rare earth element (REE) compositions of vertebrate microremains of the Vesiku Bone Bed (Homerian, Wenlock), Saaremaa Island, Estonia. Estonian journal of earth sciences, 64(1), 36-41
Open this publication in new window or tab >>Palaeoenvironmental signatures revealed from rare earth element (REE) compositions of vertebrate microremains of the Vesiku Bone Bed (Homerian, Wenlock), Saaremaa Island, Estonia
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2015 (English)In: Estonian journal of earth sciences, ISSN 1736-4728, E-ISSN 1736-7557, Vol. 64, no 1, p. 36-41Article in journal (Refereed) Published
Abstract [en]

Rare earth elements (REEs) have been analysed from fossil vertebrate microremains (thelodont scales) from the Vesiku Bone Bed, Saaremaa, Estonia, using in situ microsampling by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Well-preserved scales of three species of the genus Thelodus (T. carinatus, T. laevis and Thelodus sp.) show very uniform REE patterns with slightly lower overall REE concentrations in enameloid than in dentine, with enrichment in middle REEs, depletion in heavy REEs and pronounced negative europium anomaly, but no cerium anomaly. The results of this study suggest a similar diagenetic history and possibly contemporaneous habitats for all three Thelodus species, as well as possible suboxic to anoxic conditions of the bottom and pore waters during the formation of the Vesiku Bone Bed.

Keyword
Vesiku Bone Bed, rare earth element, REE, palaeoenvironment, thelodonts, Silurian
National Category
Developmental Biology Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-251825 (URN)10.3176/earth.2015.07 (DOI)000351327700008 ()
Available from: 2015-04-27 Created: 2015-04-24 Last updated: 2017-12-04Bibliographically approved
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