| 1. |
- Roy, Jean-Claude, et al.
(author)
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The ORS Vertebrates of Spitsbergen (Svalbard)
- 2010
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In: Résumés. ; , s. 223-223
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Conference paper (other academic/artistic)abstract
- In the Arctic, Spitsbergen (Svalbard archipelago) comprises a Caledonian metamorphic basement structured around 420 Ma, cut by faults that demarcate a sedimentary, NS graben, filled up by siliclastic detrital series of Old Red Sandstone facies (ca. 418 - ca. 326 Ma), with a lateral cumulative thickness of 6300 to more than 10,800 meters. The latter yields a particularly abundant fauna of early fishes, which are the main guide fossils for stratigraphic purposes (Agnatha, Placodermi and Crossopterygii). These sediments are faulted and folded, and disconformably overlapped by the unfolded, marine Carboniferous - Permian carbonate platform. The Old Red Sandstone of Spitsbergen is a reference for all the contemporaneous series of the ORS Continent. However, since the outcrops were hitherto discontinuous in the Polar zone, the stratigraphic correlations were difficult to establish, and the definition of the lithostratigraphic units are still discussed. This region is one of the least studied as for paleontology and stratigraphy, even if several fossil collections and partial field mappings have been made, notably in 1939 with the Anglo-Norwegian-Swedish palaeontological expedition, and in 1969 with the French CNRS-MNHN expedition, later completed by the Russian and German works (Murasov and Mokin 1976, 1979; Schweitzer, 1999). Since the acceleration of the melting of the glaciers and of the ice-cap, the gradual continental rise by glacioisostasy and the erosion by torrents and the tide cause incisions in the moraines, and new outcrops appear. In the framework of a collaboration with the Norsk Polarinstitutt, our field teams could visit some of them, such as LGGST - Chorowicz 1986 to 1994, Roy 1999, CAST 401 IFRTP - ipev 2002 and 2003, Roy 2008, and SPITZ P3 1005 ipev 2010, and the stratigraphical correlation of the nunataks is in progress. Palaeontology, geology, geophysical and geochimical geochronology show that, in Spitsbergen, the deposition of the ORS began in Late Silurian (?Pridoli) times and continued in the Devonian and Carboniferous until the beginning of the late Mississipian. The new information we now have, thanks to studies led in the framework of the International Geologic Correlation Programme 328 (Blieck and Turner 2000) and IGCP 406 Programme, 'Circum Arctic Lower - Middle Paleozoic Vertebrate Palaeontology and Biostratigraphy', with H. Blom (Uppsala) and V. Talimaa (Vilnius), lead us to consider the sedimentation of the graben and its tectonic behaviour as an essential source of data for understanding the natural history of the Arctic: the consequences of the closure of the Iapetus ocean and the dismantling of the Caledonian chain. The bio- and litho- stratigraphy begins to be accurately known, notably thanks to the vertebrate-based biozones (Agnatha, Placodermi and Crossopterygii); a work that was been initiated by Daniel Goujet (1984) and continued by the research team on vertebrate fossils of Spitsbergen (Blieck, 1982, 1984; Goujet, 1984; Janvier 1985; Blieck et al., 1987; Clément, 2001; Pernegre, 2004). If some of these vertebrates seem endemic to Spitsbergen and to the Arctic, they are closely connected to marine species of global distribution, notably with Australian species.
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| 2. |
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| 3. |
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| 4. |
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| 5. |
- Dupret, Vincent, et al.
(author)
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A primitive placoderm sheds light on the origin of the jawed vertebrate face
- 2014
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 507:7493, s. 500-503
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Journal article (peer-reviewed)abstract
- 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.
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| 6. |
- Dupret, Vincent, 1977-, et al.
(author)
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Being Romundina stellina Ørvig, 1975 (Vertebrate, Placodermi, Acanthothoraci) : itracranial anatomy of one of the deepest gnathostomes revealed by synchrotron tomograpy in phase contrast protocole
- 2012
-
Conference paper (peer-reviewed)abstract
- 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. References1 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).
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| 7. |
- Dupret, Vincent, 1977-, et al.
(author)
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Bone vascularization and growth in placoderms (Vertebrata) : The example of the premedian plate of Romundina stellina Ørvig, 1975
- 2010
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In: Comptes rendus. Palevol. - : Elsevier BV. - 1631-0683 .- 1777-571X. ; 9:6-7, s. 369-375
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Journal article (peer-reviewed)abstract
- The Placodermi (armored jawed fishes), which appeared during the Lower Silurian and disappeared without leading any descendants at the end of the Famennian (Latest Devonian), have the highest diversity of known Devonian vertebrate groups. As phylogenetically basal gnathostomes (jawed vertebrates), they are potentially informative about primitive jawed vertebrate anatomy and origins. Until recently, the study of their internal or histological structures has required destructive methods such as sectioning or serial grinding. Recent advances in tomography and imaging technologies, especially through the increasing use of synchrotron phase contrast imaging for the study of fossils, allow us to reveal the inner structures of the fossil nondestructively and with unprecedented three-dimensional level of detail. Here, we present for the first time the prerostral anatomy of the small acanthothoracid Romundina stellina, one of the earliest and most basal placoderms. Phase contrast imaging allows us to reconstruct the vascularization and nerve canals of the premedian plate and adjacent parts of the skeleton three-dimensionally in great detail, providing important clues to the growth modes and biology of the animal.
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| 8. |
- Dupret, Vincent, et al.
(author)
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First Perigondwanan record of actinolepids (Vertebrata: Placodermi: Arthrodira) from the Lochkovian (Early Devonian) of Spain and its palaeobiogeographic significance
- 2011
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In: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 310:3-4, s. 273-282
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Journal article (peer-reviewed)abstract
- Different palaeogeographic models have been proposed for the position of Laurussia ( including Baltica) and Gondwana-derived microcontinents ( including Ibero-Armorica) during Ordovician to Late Carboniferous times. Principal differences concern the presence and duration of a large ocean, the Rheic Ocean, acting as a faunal barrier between these areas. The timing of the collision of Laurussia with Gondwana and/or Gondwana-derived terranes continues to be debated. Here we present new faunal data revealing close biogeographical relations between Ibero-Armorica ("Perigondwanan" or Gondwanan derivate terranes) and Podolia (SE margin of Baltica, in Laurussia). The placoderm assemblage found in the mid-late Lochkovian (Lower Devonian) of Celtiberia (north-central Spain), consisting of the 'actinolepid' species Kujdanowiaspis podolica, Erikaspis zychi and the acanthothoracid Palaeacanthaspis aff. P. vasta, is similar, both in terms of taxonomy and stratigraphic record, to that encountered in the Lochkovian of Podolia (Ukraine; Laurussia) and until now considered as endemic to this region. Moreover, vertebrate faunal links between Podolia and Celtiberia are also extended to the chondrichthyan scale-based species Seretolepis elegans and Altholepis composita previously documented exclusively from Laurussian localities (Podolia and Mackenzie Mountains in Canada), which occur together with the placoderm remains described herein. These evidences support the hypothesis that intermittent shallow neritic migration paths between Podolia (as well as "Avalonia") and Iberia existed in the late Lochkovian, agreeing with a palaeogeographic reconstruction showing close proximity between peri-Gondwanan or Gondwana-derived terranes and Laurussia. It supports the palaeogeographic model of the non-oceanic Variscan Mobile Crustal Field and it corroborates the arguments against wide oceans, acting as biogeographical relevant barriers, between Baltica and Gondwana in early Devonian times. The distribution patterns of heavy-shelled ostracods, turbidicolous brachiopods, and Rhenish trilobites also support these conclusions.
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| 9. |
- Dupret, Vincent, 1977-, et al.
(author)
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Fossil early vertebrates shed lights on the origin of the gnathostome face
- 2013
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In: Program and Abstracts of the 10th International Congress of Vertebrate Morphology. - Barcelona, Spain. ; , s. 245-245
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Conference paper (peer-reviewed)abstract
- 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.
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| 10. |
- Dupret, Vincent, 1977-, et al.
(author)
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Fossils of early vertebrates and the evolution of the gnathostome face revealed by Synchrotron imaging
- 2013
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In: Programme and Abstracts. - Edinburgh, U.K.. ; , s. 21-21
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Conference paper (peer-reviewed)abstract
- 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.
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| 11. |
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| 12. |
- Dupret, Vincent, 1977-, et al.
(author)
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Intracranial anatomy of Romundina stellina Ørvig 1975 (Vertebrata, Placodermi, Acanthothoraci) revealed by phase contrast synchrotron imaging
- 2011
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In: Abstracts. ; , s. 6-6
-
Conference paper (other academic/artistic)abstract
- 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.
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| 13. |
- Dupret, Vincent, et al.
(author)
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New cranial material of the acanthothoracid placoderm Palaeacanthaspis vasta from the Lower Devonian of Podolia-phylogenetic and taxonomic significance
- 2021
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In: Acta Palaeontologica Polonica. - : INST PALEOBIOLOGII PAN. - 0567-7920 .- 1732-2421. ; 66:2, s. 337-347
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Journal article (peer-reviewed)abstract
- The Early Devonian vertebrates of Podolia in Ukraine are well known thanks to the material of the basal arthrodire placodenn genus Kujdanowiaspis, originally mentioned by Brotzen in 1934. The anatomical fame of Kujdanowiaspis brought by Erik Stensio almost eclipsed the presence of the acanthothoracid placoderm Palaeacanthapsis vasta in the underlying beds, with the original material of P. vasta being less well preserved and abundant than that of Kujdanowiaspis. Here we describe a newly discovered specimen of the acanthothoracid P. vasta from the Lochkovian of Podolia (Ukraine). The specimen, although incomplete, is very well preserved in three dimensions and allows a thorough description of its external morphology, which is compared to that of Romundina stellina and other well-known Acanthothoraci. A phylogenetic analysis is performed and the acanthothoracid nature of Palaeacanthaspis is confirmed. However, the position of Palaeacanthaspis within the Acanthothoraci remains uncertain, and its resemblance with Romundina could be due to either synapomorphies or symplesiomorphies. Similarities and differences between the two forms are exposed, and lead to the lack of synonymy at the specific level. Generic synonymy is also questioned for the first time but remains equivocal.
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| 14. |
- Dupret, Vincent, et al.
(author)
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Non-tetrapod sarcopterygians from the Valentia Slate Formation (Givetian, Devonian) of the Iveragh Peninsula, south-western Ireland: systematic reappraisal and palaeobiogeographic implications
- 2023
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In: Spanish Journal of Palaeontology. - 2255-0550 .- 2660-9568. ; 38:1, s. 37-45
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Journal article (peer-reviewed)abstract
- The Middle Devonian (Givetian) Valentia Slate Formation in the Iveragh Peninsula, southwest Ireland, is more renowned for the second oldest record of tetrapod trackways in the world than for its heavily metamorphosed bone remains. The present study focuses on new discoveries of non-tetrapod sarcopterygian fish fossils from the Valentia Slate Formation. Micro-CT scanning technology allows a re-interpretation of a previously published acanthodian fin spine as a fanged coronoid of a probable Rhizodontida and the identification of a Dipnoi tooth plate and bone. In addition, a scale of Holoptychius is described. The presence of rhizodontids suggests Gondwanan ties, and a first northward dispersal wave of these vertebrates into Euramerica as early as middle Givetian. This hypothesis is supported by the common occurrence of the placoderm Bothriolepis in the Valentia Slate Formation.
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| 15. |
- Dupret, Vincent, et al.
(author)
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Redescription of Szelepis Liu, 1981 (Placodermi, Arthrodira), from the Lower Devonian of China
- 2017
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In: Journal of Vertebrate Paleontology. - : Informa UK Limited. - 0272-4634 .- 1937-2809. ; 37:2
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Journal article (peer-reviewed)abstract
- The skull roof of the species Szelepis yunnanensis (Liu, 1979) from the Early Devonian of Yunnan is redescribed, as well as other Szelepis material previously published. It appears that only the holotype of S. yunnanensis can be confidently assigned to this genus. The fusion of the preorbital plates into one plate strongly suggests the assignment of Szelepis yunnanensis to the monophyletic family Actinolepididae Gross, 1940, sensu stricto (comprising Actinolepis Agassiz, 1884, and Bollandaspis Schmidt, 1979). This is confirmed by a phylogenetic analysis. Hence, Szelepis constitutes the most ancient occurrence of the family but not the sister group to the remaining members.
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| 16. |
- Dupret, Vincent, 1977-
(author)
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Revision of the genus Kujdanowiaspis Stensiö, 1942 (Placodermi, Arthrodira, "Actinolepida") from the Lower Devonian of Podolia (Ukraine)
- 2010
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In: Geodiversitas. - : Museum National d'Histoire Naturelle, Paris, France. - 1280-9659 .- 1638-9395. ; 32, s. 5-63
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Journal article (peer-reviewed)abstract
- The genus Kujdanowiaspis Stensiö, 1942 has long been considered as the archetype of placoderms; hence, it has been often used as outgroup in phylogenetic analyses involving placoderms, or used as a representative of all the placoderms for all early vertebrate works. Nevertheless, there has been no real work on the taxonomy of this genus since Denison (1978). Here we propose a revision of the material of Kujdanowiaspis from the Old Red Sandstone of Podolia (including neurocrania, skull roofs and thoracic armours), together with the description of unpublished specimens of the genus Heightingtonaspis White, 1969. Among the available Podolian material, three species are considered valid: Kujdanowiaspis buczacziensis (Brotzen, 1934), K. podolica (Brotzen, 1934) and Erikaspis zychi (Stensiö, 1945) (K. podolica and K. buczacziensis only differ in size and in the density and size of the tuberculated ornamentation; the dermal plate pattern of E. zychi differs from that of the genus Kujdanowiaspis). The axillar area of the scapulocoracoid of K. podolica is compared with those of an osteostracan “agnathan” and of a non-tetrapod sarcopterygian. In the three cases, the articulation of the pectoral fin is of the monobasal type. An analogy with the embryonic development of the pectoral fin of the actinopterygian Danio rerio (Hamilton, 1822) suggests that the monobasal articulation would correspond to the plesiomorphic condition compared with the multibasal one of the adult actinopterygians and some derived brachythoracid placoderms. The suprasynarcual is a newly identified, chondrified element of the vertebral column, supposed to respond to the height of the median dorsal plate in Kujdanowiaspis podolica.
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| 17. |
- Dupret, Vincent, 1977-, et al.
(author)
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Structures intra-crâniennes de Romundina stellina Ørvig 1975 (Vertebrata, Placodermi, Acanthothoraci) révélé par tomographie synchrotron en contraste de phase
- 2012
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Conference paper (peer-reviewed)abstract
- 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.
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| 18. |
- Dupret, Vincent, et al.
(author)
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The Bothriolepis (Placodermi, Antiarcha) material from the Valentia Slate Formation of the Iveragh Peninsula (middle Givetian, Ireland) : Morphology, evolutionary and systematic considerations, phylogenetic and palaeogeographic implications
- 2023
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 18:2
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Journal article (peer-reviewed)abstract
- Material of the antiarch placoderm Bothriolepis from the middle Givetian of the Valentia Slate Formation in Iveragh Peninsula, Ireland, is described and attributed to a new species, B. dairbhrensis sp. nov. A revision of the genus Bothriolepis is proposed, and its taxonomic content and previous phylogenetic analyses are reviewed, as well as the validity of morphologic characteristics considered important for the establishment of the genus, such as the shape of the preorbital recess of the neurocranium. A series of computerised phylogenetic analyses was performed, which reveals that our new species is the sister taxon to the Frasnian Scottish form B. gigantea. New phylogenetic and biogeographic analyses of the genus Bothriolepis together with comparisons between faunal assemblages reveal a first northward dispersal wave from Gondwana to Euramerica at the latest in the mid Givetian. Other Euramerican species of Bothriolepis seem to belong to later dispersal waves from Gondwana, non-excluding southward waves from Euramerica. Questions remain open such as the taxonomic validity and stratigraphic constraints for the most ancient forms of Bothriolepis in China, and around the highly speciose nature of the genus.
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| 19. |
- Dupret, Vincent, 1977-, et al.
(author)
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The cranial anatomy of Romundina stellina Ørvig, 1975 (Vertebrata, Placodermi, Acanthothoraci) revealed by phase contrast synchrotron scanning
- 2010
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Conference paper (pop. science, debate, etc.)abstract
- 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.
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| 20. |
- Dupret, Vincent, et al.
(author)
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The internal cranial anatomy of Romundina stellina Orvig, 1975 (Vertebrata, Placodermi, Acanthothoraci) and the origin of jawed vertebrates : Anatomical atlas of a primitive gnathostome
- 2017
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:2
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Journal article (peer-reviewed)abstract
- 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.
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| 21. |
- Dupret, Vincent, 1977-, et al.
(author)
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The origin of the jawed vertebrate face : new insights from a synchrotron scanned skull of the primituve placoderm Romundina
- 2013
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In: Program and abstracts. - Los Angeles, U.S.A.. ; , s. 118-118
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Conference paper (other academic/artistic)abstract
- 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.
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| 22. |
- Dupret, Vincent, 1977-, et al.
(author)
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The Placoderm Romundina and the Origin of the Gnathostome Face
- 2013
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In: The Making of a Vertebrate. - Kobe, Japan. ; , s. 110-111
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Conference paper (peer-reviewed)abstract
- 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.
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| 23. |
- Dupret, Vincent, 1977-, et al.
(author)
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The skull of Hagiangella goujeti Janvier, 2005, a high-crested acanthothoracid (Vertebrata, Placodermi) from the Lower Devonian of northern Vietnam
- 2011
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In: Journal of Vertebrate Paleontology. - : Informa UK Limited. - 0272-4634 .- 1937-2809. ; 31:3, s. 531-538
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Journal article (peer-reviewed)abstract
- The acanthothoracid Hagiangella goujeti Janvier, 2005, has been described exclusively on the basis of isolatedthoracic plates from the Lochkovian (Lower Devonian) Khao Loc Formation of Tung Vai, Ha Giang Province, northernVietnam. It is characterized by a very high, triangular median crest on the median dorsal plate, and has been referred to theAcanthothoraci on the basis of the morphology of its fused anterolateral, spinal and anterior ventrolateral plates, and thecharacteristic stellate ornamentation of the group. Isolated plates of H. goujeti are relatively abundant at Tung Vai and noother placoderm taxon from this locality seems to share the same type of ornamentation. However, the skull of this speciesremained elusive. Here we report two well-preserved skull roofs from Tung Vai, which we refer to H. goujeti. They display thesame stellate ornamentation and small size as the previously described plates of the thoracic armor of this species. This newmaterial shows that the head of H. goujeti is surprisingly short (i.e., possibly lacking dermal rostral and pineal elements), incontrast to the elongate and narrow skull of all other acanthothoracids. The combination of unique characters (e.g., presenceof two pairs of posterior pit lines, two pairs of central and paranuchal plates, etc.) suggests a possible sister group relationshipto the placoderm assemblage Petalichthyida + Ptyctodontida + Arthrodira.
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| 24. |
- Dupret, Vincent, 1977-, et al.
(author)
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Vertebrate macroremains as stratigraphic markers : the case of the Lower Devonian “Kujdanowiaspis assemblage” from Podolia (Ukraine) and Celtiberia (Spain)
- 2010
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Conference paper (other academic/artistic)abstract
- The vertebrate fauna, including chondrichthyan microremains and osteostracan and placoderm macroremains encountered in the Lower Devonian (i.e. Lochkovian and Pragian) deposits from Podolia (Ukraine; see list in Voichyshyn, 2001) was considered as unique. Unfortunately, because of the Old Red Sandstone facies, the stratigraphic boundaries were very difficult to determine. Until recently, most of the units were lithologic. The occurrence of the arthrodire placoderm Kujdanowiaspis buczacziensis has since been proposed to mark the beginning of the Pragian, owing to a number of correlations between fossil distributions (i.e. the pteraspidiform Althaspis) in Western Europe and Podolia (Dupret and Blieck, 2009).Recently, the long time “unique” placoderm and chondrichthyan faunal assemblage from Podolia has been found in Spain (Martinez-Pérez et al., in press; Dupret et al., submitted). The absence of K. buczacziensis, nevertheless, leads us to consider an age older than Pragian, i.e. late Lochkovian. This dating confirms previous works mainly based on invertebrates and conodonts. These “double check” processes confirm the possibility of using macrovertebrate remains for stratigraphic purposes.The occurence of the same fauna during the Late Lochkovian in Podolia (southern margin of Laurussia) and in Spain (Armorican ”block”, part of northern margin of Gondwana or independant component), leads us to favour palaeogeographic reconstructions showing a proximity between both palaeo-provinces, allowing for the formation of, at least, punctual migratory paths. Moreover, the Old Red Sandstones have long been considered as non-marine deposits, especially in Podolia, despite the discovery of seldom brachiopod (lingulid) fragments. The similar faunal composition between Podolia and Celtiberia (the latter being clearly marine) challenges the non-marine status of the Podolian deposits.
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| 25. |
- Herbin, Marc, et al.
(author)
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Les techniques d’imagerie 3D au service de la valorisation scientifique des collections anatomiques
- 2010
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In: La Lettre de l'OCIM. - 0994-1908. ; 131, s. 13-18
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Journal article (peer-reviewed)abstract
- The presentation of this virtual study of the anatomy of a Coelacanthe specimen produced using three dimensional x ray imaging and magnetic resonance notably brings light to the possibilities of application of these technologies – which avoid repetitive manipulations and preserve the morphological integrity of precious and scientifically important specimens – in the field of scenography or of preventive conservation.
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| 26. |
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| 27. |
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| 28. |
- Olive, Sebastien, et al.
(author)
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A new species of Groenlandaspis Heintz, 1932 (Placodermi, Arthrodira), from the Famennian (Late Devonian) of Belgium
- 2015
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In: Journal of Vertebrate Paleontology. - : Informa UK Limited. - 0272-4634 .- 1937-2809. ; 35:4
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Journal article (peer-reviewed)abstract
- A new species of the phlyctaeniid arthrodire genus Groenlandaspis from the upper Famennian of Belgium is described. The remains of Groenlandaspis potyi, sp. nov., consist of dissociated thoracic armor elements, but the specimen designated to be the holotype displays the median dorsal, anterior, and posterior dorsolateral plates in articulation. Though incomplete, the new species is characterized by an equilateral triangle-shaped median dorsal plate, a protruding posterodorsal apron of the posterior dorsolateral plate behind the overlap area for the median dorsal plate, and an overall lack of ornamentation. Groenlandaspis potyi, sp. nov., constitutes the second occurrence of a Groenlandaspis species in continental Europe after the description of Groenlandaspis thorezi from upper Famennian quarries of Belgium. Another probable new species of Groenlandaspis is also described, though of unknown locality and horizon; it can, however, be deduced to be from the upper Famennian of Belgium without more precision. Together with some unpublished material of groenlandaspidids from the Famennian tetrapod-bearing locality of Strud, this material highlights the richness of Groenlandaspididae diversity in Belgium. The discovery of Groenlandaspis potyi, sp. nov., in Belgium reinforces the Famennian global distribution of this genus during this period. Also, because these organisms have been considered as non-marine indicators, this material is another argument pleading for close relationships between Euramerica and Gondwana around the Frasnian-Famennian boundary.
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| 29. |
- Olive, Sebastien, et al.
(author)
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Characterization of the placoderm (Gnathostomata) assemblage from the tetrapod-bearing locality of Strud (Belgium, upper Famennian)
- 2015
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In: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 58:6, s. 981-1002
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Journal article (peer-reviewed)abstract
- The placoderm fauna of the late Famennian tetrapod-bearing locality of Strud, Belgium, is studied on the basis of historical and newly collected material. It includes the previously described antiarch Grossilepis rikiki, the groenlandaspidid Turrisaspis strudensis sp. nov. and the actinolepidoideid Phyllolepis undulata. P.undulata is thoroughly described and joins the list of the valid Phyllolepis species confidently diagnosed. A morphometrical analysis performed on the centronuchal and anterior ventrolateral plates of the Phyllolepis material demonstrates that there is only one species of Phyllolepis in Belgium (thus, Phyllolepis konincki becomes a junior synonym of P.undulata), that P.rossimontina (Pennsylvania) is a synonym of P.undulata and that the unity of the genus Phyllolepis is strongly supported, although the characterization of several species within this genus is blurred. The strong resemblance between the faunal compositions in Strud and Red Hill (Pennsylvania, USA) suggests important faunal exchanges between these regions of the Euramerica landmass.
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| 30. |
- Olive, Sebastien, et al.
(author)
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Flora and fauna from a new Famennian (Upper Devonian) locality at Becco, eastern Belgium
- 2015
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In: Geologica Belgica. - 1374-8505 .- 2034-1954. ; 18:2-4, s. 92-101
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Journal article (peer-reviewed)abstract
- The Becco locality (Liege province), belongs to the Theux tectonic window and represents a proximal, probably fluvial, environment corresponding to a channel infill. We present here a preliminary report of the fossil assemblage discovered at the locality. The Becco site has yielded a diverse flora of early seed plants including Moresnetia zalesskyi, Dorinnotheca streeli and Condrusia sp. This assemblage, characteristic of the Belgian Famennian, highlights the diversity of early spermatophytes in the country. Becco has also delivered a rich vertebrate fauna with antiarch, groenlandaspid and phyllolepid placoderms, diplacanthiform acanthodians, as well as actinopterygians and various sarcopterygians. The fossiliferous assemblage of Becco resembles those of several Devonian tetrapod-bearing localities, including that of Strud in Belgium, and could therefore provide a favorable palaeoecological setting in the search for early tetrapods.
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| 31. |
- Olive, Sebastien, et al.
(author)
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Placoderm Assemblage from the Tetrapod-Bearing Locality of Strud (Belgium, Upper Famennian) Provides Evidence for a Fish Nursery
- 2016
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:8
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Journal article (peer-reviewed)abstract
- The placoderm fauna of the upper Famennian tetrapod- bearing locality of Strud, Belgium, includes the antiarch Grossilepis rikiki, the arthrodire groenlandaspidid Turrisaspis strudensis and the phyllolepidid Phyllolepis undulata. Based on morphological and morphometric evidence, the placoderm specimens from Strud are predominantly recognised as immature specimens and this locality as representing a placoderm nursery. The Strud depositional environment corresponds to a channel in an alluvial plain, and the presence of a nursery in such environment could have provided nutrients and protection to the placoderm offspring. This represents one of the earliest pieces of evidence for this sort of habitat partitioning in vertebrate history, with adults living more distantly from the nursery and using the nursery only to spawn or give live birth.
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| 32. |
- Sanchez, Sophie, et al.
(author)
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3D Microstructural Architecture of Muscle Attachments in Extant and Fossil Vertebrates Revealed by Synchrotron Microtomography
- 2013
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:2, s. e56992-
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Journal article (peer-reviewed)abstract
- 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.
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| 33. |
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| 34. |
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| 35. |
- Trinajstic, Kate, et al.
(author)
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Exceptional preservation of organs in Devonian placoderms from the Gogo lagerstätte
- 2022
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 377:6612, s. 1311-1314
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Journal article (peer-reviewed)abstract
- The origin and early diversification of jawed vertebrates involved major changes to skeletal and soft anatomy. Skeletal transformations can be examined directly by studying fossil stem gnathostomes; however, preservation of soft anatomy is rare. We describe the only known example of a three-dimensionally mineralized heart, thick-walled stomach, and bilobed liver from arthrodire placoderms, stem gnathostomes from the Late Devonian Gogo Formation in Western Australia. The application of synchrotron and neutron microtomography to this material shows evidence of a flat S-shaped heart, which is well separated from the liver and other abdominal organs, and the absence of lungs. Arthrodires thus show the earliest phylogenetic evidence for repositioning of the gnathostome heart associated with the evolution of the complex neck region in jawed vertebrates.
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| 36. |
- Trinajstic, Kate, et al.
(author)
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Fossil Musculature of the Most Primitive Jawed Vertebrates
- 2013
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 341:6142, s. 160-164
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Journal article (peer-reviewed)abstract
- 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.
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| 37. |
- Trinajstic, Kate, et al.
(author)
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Response to comment on "Exceptional preservation of organs in Devonian placoderms from the Gogo largerstätte"
- 2023
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 380:6645
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Journal article (other academic/artistic)abstract
- Jensen et al. (1) question evidence presented of a chambered heart within placoderms, citing its small size and apparently ventral atrium. However, they fail to note the belly-up orientation of the placoderm within one nodule, and the variability of heart morphology within extant taxa. Thus, we remain confident in our interpretation of the mineralized organ as the heart.
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| 38. |
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