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  • 1.
    Balthasar, Uwe
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Skovsted, Christian B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Brock, A
    Department of Biological Sciences, Macquarie University, Australia .
    Homologous skeletal secretion in tommotiids and brachiopods2009In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 37, no 12, p. 1143-1146Article in journal (Refereed)
    Abstract [en]

    Tommotiids are distinctive components of the early Cambrian small shelly fauna, almost invariably represented by isolated phosphatic sclerites derived from a multielement protective cover (scleritome). The unusual range of tommotiid sclerite morphologies and unknown construction of the scleritome have severely hampered our understanding of their phylogenetic affinities. However, recent description of rare, articulated scleritome material belonging to the tommotiid genera Eccentrotheca and Paterimitra support the hypothesis that some tommotiids fall within the stem group of the lophophorate phyla Phoronida and Brachiopoda and that at least some tommotiid sclerites are homologous precursors of the shells of organophosphatic brachiopods. Here we show that the shell microstructure of Eccentrotheca and Paterimitra share substantial similarities with paterinid brachiopods. While paterinids possess an overall brachiopod morphology, their microstructure appears more similar to Eccentrotheca and Paterimitra than to nonpaterinate lingulids. These findings strongly support the existence of a brachiopod total group that is solidly rooted within tommotiids, and identify the organophosphatic skeletal composition as plesiomorphic with calcareous shells as derived. The microstructural changes of the proposed tommotiid-brachiopod transition probably reflect an adaptation to fluctuating food and phosphorous intake that came with the switch to a sessile life style at the base of the tommotiid clade.

  • 2.
    Gubanov, Alexander P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Skovsted, Christian B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Peel, John S.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. Uppsala University, Music and Museums, Museum of Evolution.
    Anabarella australis (Mollusca, Helcionelloida) from the Lower Cambrian of Greenland2004In: Geobios, ISSN 0016-6995, E-ISSN 1777-5728, Vol. 37, no 6, p. 719-724Article in journal (Refereed)
    Abstract [en]

    The Early Cambrian helcionelloid mollusc Anabarella australis is described from North-East Greenland, representing the second occurrence of the species outside of Australia. Other Australian molluscs of this age are known from many localities including North China, Siberia, Altai, Transbaikalia, southern Kazakhstan, Mongolia, eastern Germany and Spain. These records, supported now by A. australis, demonstrate the close proximity of continents in the Early Cambrian.

  • 3.
    Holmer, Lars E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Pettersson Stolk, Sandra
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Skovsted, Christian B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Balthasar, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Popov, Leonid
    Department of Geology, National Museum of Wales,Cardiff Wales, UK.
    The enigmatic early cambrian salanygolina: a stem group of rhynchonelliform chileate brachiopods?2009In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 52, no 1, p. 1-10Article in journal (Refereed)
    Abstract [en]

    New material of the enigmatic brachiopod Salanygolina obliqua Ushatinskaya from the Early Cambrian of Mongolia shows that it has a colleplax- a triangular plate - in the umbonal perforation, which is enlarged by resorption. This structure is otherwise only known from the equally enigmatic Palaeozoic orders Chileida and Dictyonellida (Rhynchonelliformea, Chileata). The colleplax in Salanygolina is here considered to be homologous with that of the chileates. Salanygolina is also provided with a ridge-like pseudodeltidium, which is another chileate feature. Other characters of Salanygolina, like the radial arrangement of adductor muscle scars and postero-medially placed internal oblique muscles are characteristic of chileates, but also found in the paterinates. In contrast, mixoperipheral dorsal valves with low rudimentary interareas are well known in paterinates, but not yet recorded from chileates. Thus, Salanygolina shows a mosaic combination of morphologic characters, known both from the paterinates and chileates, indicating that it may represent a stem group of the rhynchonelliform chileate brachiopods. The laminar phosphatic secondary shell of Salanygolina is composed of closely packed and nearly identical hexagonal prisms, oriented with their long axis normal to the laminae in a honeycomb pattern. The prism walls appear to have originally been composed of organic membranes and might represent precursors of the organic sheaths of calcite fibers that are typical of calcitic shells with a fibrous microstructure.

  • 4.
    Holmer, Lars E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Skovsted, Christian B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Larsson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Brock, Glenn A.
    Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia.
    Zhang, Zhifei
    Early Life Institute, State Key Laboratory of Continental Dynamics, Northwest University, Xi’an 710069, China.
    First record of a bivalved larval shell in Early Cambrian tommotiids and its phylogenetic significance2011In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 54, no 2, p. 235-239Article in journal (Refereed)
    Abstract [en]

    Brachiopods are marine Lophotrochozoa whose soft parts are enclosed in a bivalved shell. Although brachiopods are represented by a rich record from the Early Cambrian to the present, the origin of their bivalved body plan remains controversial. The Early Cambrian organophosphatic tommotiids Micrina and Paterimitra from Australia have been proposed as stem brachiopods. Here, we describe their earliest ontogeny, indicating that tommotiids possessed bivalved planktotrophic larvae. The curious combinations of characters in Micrina and Paterimitra indicate that they may belong to the stems of the Linguliformea and Rhynchonelliformea, respectively. The bivalved shell of adult living brachiopods may represent a plesiomorphic character retained from planktic tommotiid larvae; the crown group body plan of the Brachiopoda may have evolved through the paedomorphic retention of a bivalved larval state.

  • 5.
    Holmer, Lars E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Skovsted, Christian B.
    Uppsala University.
    Williams, Alwyn
    University of Glasgow, UK.
    A stem group brachiopod from the Lower Cambrian - support for a Micrina (Halkieriid) ancestry.2002In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 45, no 5, p. 875-882Article in journal (Refereed)
    Abstract [en]

    The shell structure of the Lower Cambrian Mickwitzia, a bilaterally symmetrical bivalve hitherto doubtfully assigned to the Brachiopoda, confirms that the genus shares characters with linguliform brachiopods. The columnar lamination of its organophosphatic shell is homologous with that characterizing acrotretides. The shell, however, is also pervaded by striated apatitic tubes indistinguishable from those permeating the sclerites of the problematic organophosphatic, laminar–shelled Micrina which is close to Halkieria. No crown group brachiopods have such tubes that are presumed to have contained setae. The presence of both these features in the Mickwitzia shell suggests that the stock is a stem group brachiopod with a halkieriid ancestry.

  • 6.
    Holmer, Lars
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Skovsted, Christian
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Brock, Glenn A.
    The expanding brachiopod stem-group – First record of Mickwitzia from the Early Cambrian of South Australia2007In: 51st Palaeontological Association Annual Meeting: Programme with Abstracts, 2007, p. 37-Conference paper (Other scientific)
    Abstract [en]

    New findings of Mickwitzia in the Flinders Ranges of South Australia represent the first record of this important genus in eastern Gondwana and show that it had a nearly global distribution in the Early Cambrian. The new fossils come from the late Early Cambrian Ajax Limestone (Pararaia tatei trilobite biozone – late Atdabanian-Botoman equivalent) of Mount Scott in the Flinders Ranges, South Australia. The new Australian Mickwitzia show distinct similarities with the roughly coeval material from Canada, including evidence for a possible pedicle foramen. Mickwitzia is regarded to be a derived member of the brachiopod stem group and combine important traits of crown group brachiopods with characters that are otherwise found among the problematic, tommotiids (sensu lato), particularly Micrina. Most importantly the shells of Micrina and Mickwitzia are provided with penetrative setal canals that have been recorded in all available material of mickwitziids, including the new Australian material. Recent studies have showed that shell penetrative setae are more widely distributed among brachiopods than previously thought, and even are retained in some rhynchonelliform lineages.

  • 7.
    Skovsted, C. B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Brock, A
    Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
    Holmer, L. E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Paterson, R
    Division of Earth Sciences, School of Environmental and Rural Science, University of New England, Armidale NSW 2351, Australia.
    First report of the early Cambrian stem group brachiopod Mickwitzia from East Gondwana2009In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 16, no 1, p. 145-150Article in journal (Refereed)
    Abstract [en]

    The first mickwitziid brachiopod, Mickwitzia sp.. from East Gondwana is described from the lower Cambrian Ajax Limestone, Mt Scott Range in South Australia. The shells are fragmentary, but preserve sufficient details of morphology and micro-structure to allow positive identification to genus. The morphology of the dorsal valve apex and the extended cones on the internal surface indicate a close affinity with Mickwitzia muralensis Walcott, 1913 from the early Cambrian of British Columbia, but Scarcity of material precludes detailed comparison. This find extends the known range of the pivotal stem group brachiopod Mickwitzia to East Gondwana. (C) 2009 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

  • 8.
    Skovsted, Christian B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Brock, Glenn A.
    Centre for Ecostratigraphy and Palaeobiology, Department of Earth and Planetary Sciences, Macquarie University, Australia .
    Paterson, John R.
    Division of Earth Sciences, School of Environmental and Rural Science, University of New England, Armidale Australia .
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Budd, Graham E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    The scleritome of Eccentrotheca from the Lower Cambrian of South Australia: Lophophorate affinities and implications for tommotiid phylogeny2008In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 36, no 2, p. 171-174Article in journal (Refereed)
    Abstract [en]

    The first partially articulated scleritome of a tommotiid, Eccentrotheca sp., is described from the Lower Cambrian of South Australia. The Eccentrotheca scleritome consists of individual sclerites; fused in a spiral arrangement, forming a tapering tube-shaped skeleton with an inclined apical aperture and a circular to subcircular cross section. Traditionally, tommotiid sclerites have been assumed to form a dorsal armor of imbricating phosphatic plates in slug-like bilaterians, analogous to the calcareous sclerites of halkieriids. The structure of the Eceentrotheca scleritome is here reinterpreted as a tube composed of independent, irregularly shaped sclerites growing by basal-marginal accretion that were successively fused to form a rigid, protective tubular structure. The asymmetrical shape and sometimes acute inclination of the apical aperture suggests that the apical part of the scleritome was cemented to a hard surface via a basal disc, from which it projected vertically. Rather than being a vagrant member of the benthos, Eccentrotheca most likely represented a sessile, vermiform filter feeder. The new data suggest that the affinities of Eccentrotheca, and possibly some other problematic tommotiids, lie with the lophophorates (i.e., the phoronids and brachiopods), a clade that also possesses a phosphatic shell chemistry and a sessile life habit.

  • 9.
    Skovsted, Christian B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Brock, Glenn A.
    Topper, Timothy P.
    First occurrence of a new Ocruranus-like helcionelloid mollusc from the lower Cambrian of East Gondwana2012In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 22, no 1, p. 256-261Article in journal (Refereed)
    Abstract [en]

    A new cap-shaped mollusc, Emargimantus angulatus gen. et sp. nov. is described from the Arrowie Basin of South Australia. The new species is closely comparable to mollusc species from South China and North-East Greenland previously described under the generic name Ocruranus Liu, a genus recently reinterpreted as a multiplated, possibly polyplacophoran mollusc. Emargimantus is interpreted as a univalved helcionelloid mollusc and differs from Ocruranus in both morphology and function. E. angulatus represents the first discovery of Ocruranus-like helcionelloids in the lower Cambrian of eastern Gondwana and demonstrates that these molluscs had a global distribution during the early Cambrian.

  • 10.
    Skovsted, Christian B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Brock, Glenn A.
    Department of Biological Sciences, Macquarie University, Sydney, Australia.
    Topper, Timothy P.
    Department of Biological Sciences, Macquarie University, Sydney, Australia.
    Paterson, John R.
    Division of Earth Sciences, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Scleritome construction, biofacies, biostratigraphy and systematics of the tommotiid Eccentrotheca helenia sp. nov. from the Early Cambrian of South Australia2011In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 54, p. 253-286Article in journal (Refereed)
    Abstract [en]

    Large collections of Eccentrotheca helenia sp. nov. from the lower Cambrian Wilkawillina and Ajax limestones in the Arrowie Basin, South Australia, contain abundant low, cap-shaped and high, laterally compressed isolated sclerites in addition to partially articulated tubular specimens. The scleritome of Eccentrotheca helenia sp. nov. is fully described for the first time and shown to be formed by ontogenetic fusion of sclerites into successively stacked sclerite rings, forming a larger, tubular structure. The apical termination of the tube is highly variable, but is primarily constructed by low, cap-shaped sclerites and characterised by a central aperture of variable inclination. The adapical portion of the tube is predominantly constructed by high, laterally compressed sclerites, but individual sclerite rings can contain both cap-shaped and laterally compressed sclerites along with sclerites of intermediate morphology. The apical aperture presumably housed organic structures for attachment to a hard substrate, but the scleritome also occasionally preserves small lateral perforations between fused sclerites, which may have served to stabilise the scleritome by providing additional points of anchorage. In the Arrowie Basin, E. helenia is found in association with archaeocyath-microbial-spongiomorph-dominated bioherms and most likely inhabited pendant or cryptic habitats within these bioherms. Eccentrotheca-like sclerites form an integral part of the scleritomes of many tommotiids which may confuse taxonomic analysis. Sclerites previously assigned to 'E.' guano, consistently occur together with sclerites of Kulparina rostrata in stratigraphic intervals consistently older than strata hosting E. helenia. Rare fused specimens indicate that the sclerites of K. rostrata and 'E.' guano belong to the same scleritome.

  • 11.
    Skovsted, Christian B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Early Cambrian brachiopods from North-East Greenland2005In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 48, no 2, p. 325-345Article in journal (Refereed)
    Abstract [en]

    A diverse assemblage of late Early Cambrian brachiopods is described from the Bastion and Ella Island formations of North-East Greenland. The fauna includes nine species, representing all three extant brachiopod subphyla in addition to the stem group brachiopod Mickwitzia cf. occidens. Four linguliforms: Eoobolus priscus, Botsfordia caelata, Micromitra bella, Vandalotreta sp., three rynchonelliforms: Obolella crassa, Kutorgina reticulata, and an unidentified chileid plus a possible craniiform species occur. The fauna shows similarities to late Early Cambrian (Dyeran Stage) brachiopod faunas of eastern Canada and the United States, but also to faunas from the late Early Cambrian (Botomian–Toyonian equivalent) of Australia, Antarctica and Siberia

  • 12.
    Skovsted, Christian B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    The Early Cambrian (Botomian) stem group brachiopod Mickwitzia from Northeast Greenland2003In: Acta Palaeontologica Polonica, ISSN 0567-7920, E-ISSN 1732-2421, Vol. 48, no 1, p. 1-20Article in journal (Refereed)
    Abstract [en]

    The problematic brachiopod Mickwitzia Schmidt, 1888 is re-described based on new material of M. cf. occidens Walcott, 1908 from the Early Cambrian (Botomian) Bastion and Ella Island formations of Northeast Greenland. Etched material demonstrates that Mickwitzia has a lingulid-like juvenile ("larval") shell with trails of nick-points, reflecting the movement of marginal setae. Juvenile and early mature ventral valves have a lingulid-like pseudointerarea with a pedicle groove. The shell of M. cf. occidens is only partially phosphatic, in particular around the juvenile-early mature shell in both valves. The phosphatic shell includes at least two types of cylindrical structures: (1) slender columns identical with the columns of acrotretoid brachiopods and (2) relatively thicker tubes which may be open to the exterior surface and have internal striations (on the ventral pseudointerarea). The striations are most likely imprints of microvilli and these tubes can be inferred to have contained setae. The thinner linguliform columns and thicker setigerous striated tubes are considered to be homologous with identical structures in the sellate and mitral sclerites of the problematic Micrina, which has been identified as a probable primitive stem group of the Brachiopoda. Mickwitzia represents a more derived member of the stem group Brachiopoda.

  • 13.
    Skovsted, Christian B
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    The Lower Cambrian brachiopod Kyrshabaktella and associated shelly fossils from the Harkless Formation, southern Nevada2006In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 128, p. 327-337Article in journal (Refereed)
    Abstract [en]

    A fauna of brachiopods and small shelly fossils from the Lower Cambrian Harkless Formation of Esmeraldina County in southern Nevada is described. The brachiopod Kyrshabaktella sp. provides the first unequivocal record of lingulids in the Lower Cambrian of the Great Basin. The shells of Kyrshabaktella sp. are fragmentary, but otherwise well preserved and an acrotretid-like columnar shell structure is demonstrated. The phosphatic tubular fossil Hyolithellus insolitus is described from North America for the first time and Sphenothallus sp. provides the oldest record of this problematic genus in Laurentian strata. Other faunal elements include two additional linguliform brachiopods, echinoderm ossicles and sponge spicules.

  • 14.
    Skovsted, Christian B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Holmer, Lars E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Larsson, Cecilia M.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Högström, Anette E. S.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Brock, Glenn A.
    Department of Biological Sciences, Macquarie University New South Wales, Australia.
    Topper, Timothy P.
    Department of Biological Sciences, Macquarie University New South Wales, Australia.
    Balthasar, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Stolk, Sandra Petterson
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Paterson, John R.
    Division of Earth Sciences, School of Environmental and Rural Science, University of New England Armidale, New South Wales, Australia.
    The scleritome of Paterimitra: an Early Cambrian stem group brachiopod from South Australia2009In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 276, no 1662, p. 1651-1656Article in journal (Refereed)
    Abstract [en]

    Early Cambrian tommotiids are problematic fossil metazoans with external organophosphatic sclerites that have been considered to be basal members of the lophophorate stem group. Tommotiids are almost exclusively known from isolated or rarely fused individual sclerites, which made previous reconstructions of the actual organism highly conjectural. However, the recent discovery of the first articulated specimens of the tommotiid Eccentrotheca revealed a tubular sclerite arrangement (scleritome) that limited the possible life habit to sessile filter feeding and thus further supported a lophophorate affinity. Here, we report the first articulated specimens of a second tommotiid taxon, Paterimitra from the Early Cambrian of the Arrowie Basin, South Australia. Articulated specimens of Paterimitra are composed of two bilaterally symmetrical sclerite types and an unresolved number of small, asymmetrical and irregular crescent-shaped sclerites that attached to the anterior margin of the symmetrical sclerites. Together, the sclerites form an open cone in which the symmetrical sclerites are joined together and form a small posterior opening near the base of the scleritome, while the irregular crescent-shaped sclerites defined a broad anterior opening. The coniform scleritome of Paterimitra is interpreted to have attached to hard substrates via a pedicle that emerged through the small posterior opening ( sometimes forming a tube) and was probably a sessile filter feeder. The scleritome of Paterimitra can be derived from the tubular scleritome of Eccentrotheca by modification of basal sclerites and reduction in tube height, and probably represents a more derived member of the brachiopod stem group with the paired symmetrical sclerites possibly homologous to brachiopod valves.

  • 15.
    Skovsted, Christian
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Brock, Glenn A.
    Paterson, John R.
    Holmer, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Budd, Graham
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Eccentrotheca from the Lower Cambrian of South Australia – the first known tommotiid scleritome and its biological implications2007In: 51st Palaeontological Association Annual Meeting: Programme with Abstracts, 2007, p. 55-Conference paper (Other scientific)
    Abstract [en]

    The discovery of the first partially articulated scleritome of a tommotiid, Eccentrotheca sp. from the Lower Cambrian of the Flinders Ranges in South Australia necessitates a complete revision of the gross morphology and biological function of the problematic tommotiids. The scleritome of Eccentrotheca is an expanding tubular structure with a circular cross-section that was formed by the episodic merging of individual cone-shaped sclerites. The basal region of the tube has an open aperture, the morphology and inclination of which varies considerably. Growth patterns in the apical region indicate that the aperture housed structures that helped anchor the tube to a hard substrate. The Eccentrotheca animal is consequently reinterpreted as a sessile, epibiotic filter-feeder. This model contrasts sharply to all previously published models of tommotiid animals, which almost without exception envisages a slug-like animal with a dorsal cover of imbricating sclerites (modelled after the scleritome of the coeval halkieriid animal). Tommotiids have been suggested to fall within the stem group of the Brachiopoda, mainly based on the organophosphatic composition and brachiopod-like shell structure of some tommotiids. The sessile, filter-feeding lifestyle inferred from the scleritome of Eccentrotheca appears to strengthen the lophophorate hypothesis of tommotiid relationships, although the tubicous habit of the scleritome is more reminiscent of phoronids than brachiopods.

  • 16. Topper, Timothy P.
    et al.
    Brock, Glenn A.
    Skovsted, Christian B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Paterson, John R.
    Microdictyon plates from the lower Cambrian Ajax Limestone of South Australia: Implications for species taxonomy and diversity2011In: Alcheringa, ISSN 0311-5518, E-ISSN 1752-0754, Vol. 35, no 3, p. 427-443Article in journal (Refereed)
    Abstract [en]

    A small assemblage of isolated Microdictyon plates is described from the lower Cambrian Ajax Limestone, Mt Scott Range (Flinders Ranges), South Australia. Microdictyon plates are primarily known from single, isolated, perforated phosphatic sclerites; only one species (M. sinicum) from the Chengjiang Lagerstatte is known from soft-bodied preservation of the complete organism. The isolated plates from South Australia display a wide range of morphologies potentially reflecting: 1, considerable diversification within the group at this time; 2, extensive intraspecific morphological variation; 3, different plate morphotypes along the trunk of the animal; or 4, significant ontogenetic variation in successive growth stages. The South Australian specimens are similar to several individual sclerites described from other Cambrian palaeocontinents, but appear closest to faunas described from South China. Problems associated with the taxonomy of isolated Microdictyon plates are discussed, including the lack of knowledge associated with intraspecific and/or ontogenetic variability and how individual plate morphology may relate to size or relative position along the length of the complete organism.

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