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Gaël Clément - One of the best experts on this subject based on the ideXlab platform.
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Systematic Palaeontology (Vertebrate Palaeontology) / Paléontologie systématique First Devonian dipnoans (Vertebrata, Sarcopterygii) from Spitsbergen
2020Co-Authors: Gaël Clément, Vincent Dupret, Daniel Goujet, Vincent PernegreAbstract:AbstractFor the first time, dipnoan remains are described from the Devonian of Spitsbergen. According to the stratigraphy and theassociated vertebrate fauna, they are considered as Late Emsian–Early Eifelian in age. Unfortunately remains are too sketchy andnon-diagnostic to be referred or compared to a known Devonian dipnoan. This new material, determined as Dipnoi gen. et sp.indet., is nevertheless important in biostratigraphical and palaeobiogeographical points of view, since it is amongst the earliestdipnoan occurrences, and the first one in the Devonian of Spitsbergen. To citer this article: G. Clement et al., C. R. Palevol 5(2006).© 2006 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.ResumePremiere occurrence de dipneustes (Vertebres sarcopterygiens) dans le Devonien du Spitzberg. Des restes de dipneustesdu Devonien du Spitzberg sont decrits pour la premiere fois. D’apres la stratigraphie et la faune de vertebres associee a ces restes,ils sont consideres comme etant d’âge Emsien superieur a Eifelien inferieur. Les specimens sont malheureusement trop rares et peudiagnostiques pour pouvoir etre attribues ou meme compares aux autres dipneustes devoniens decrits. Ce nouveau materiel,determine comme Dipnoi gen. et sp. indet., est neanmoins important, du double point de vue biostratigraphique et paleobiogeo-graphique. En effet, ces specimens de dipneustes, parmi les plus anciens decouverts, sont les premiers a etre signales dans leDevonien du Spitzberg. Pour citer cet article : G. Clement et al., C. R. Palevol 5 (2006).© 2006 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
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presence of plicidentine in the oral teeth of the coelacanth latimeria chalumnae smith 1939 Sarcopterygii actinistia
Journal of Structural Biology, 2015Co-Authors: Francois J Meunier, Gaël Clément, J Mondejarfernandez, Florent Goussard, Marc HerbinAbstract:The extant coelacanth Latimeria is a sarcopterygian predatory fish with caniniform teeth on its upper and lower jaws. The teeth are constituted of a cone of dentine with an apical cap of enamel, and they are fixed to the osseous component of the jaws by an attachment bone. Internal walls of the tooth base show folds that have been firstly interpreted in the past as radial vascular canals. Three-dimensional visualisation of these foldings using X-ray tomographic techniques and new histological interpretation lead to reconsider these structures as true plicidentine. The folds of the dentine do not invade the whole pulp cavity of the tooth contrary to the plicated condition of most fossil sarcopterygian fishes (e.g., Eusthenopteron, Porolepis, Megalichthys) certain fossil marine reptiles (ichthyosaurs) and extant varanids; in Latimeria they are limited to the lower third to the half of the pulp cavity. The presence of plicidentine in Latimeria’s teeth is proposed to be a plesiomorphic character for sarcopterygians.
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the giant cretaceous coelacanth actinistia Sarcopterygii megalocoelacanthus dobiei schwimmer stewart williams 1994 and its bearing on latimerioidei interrelationships
PLOS ONE, 2012Co-Authors: Hugo Dutel, Philippe Janvier, Marc Herbin, John G Maisey, David R Schwimmer, Gaël ClémentAbstract:We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.
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The Giant Cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and Its Bearing on Latimerioidei Interrelationships
PLOS ONE, 2012Co-Authors: Hugo Dutel, Philippe Janvier, Marc Herbin, John G Maisey, David R Schwimmer, Gaël ClémentAbstract:We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.
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First occurrence of the lungfish Sagenodus (Dipnoi, Sarcopterygii) from the Carboniferous Lagerstätte of Montceau-les-Mines, France
Journal of Vertebrate Paleontology, 2012Co-Authors: Sebastien Olive, Gaël Clément, Jean-marc PouillonAbstract:ABSTRACT New material of the dipnoan genus Sagenodus is described from the Carboniferous Lagerstatte of Montceau-les-Mines, Massif Central, France. This is the first occurrence of this lungfish in France, thus enlarging its worldwide distribution; and the first occurrence of a lungfish in Montceau-les-Mines, thus increasing the vertebrate taxa list of this Lagerstatte. This material is Stephanian B in age, the previously established geological range of this Euramerican genus. Remains consist of skull, lower jaw, operculum, and shoulder girdle elements closely set together with several ribs. This material, here considered as belonging to a single disarticulated specimen, shows strong affinities with the material of Sagenodus sp. from Germany and appears significantly different from all other known species of Sagenodus by the shape and ridge pattern of the upper tooth plate. However, this new material can only be attributed to Sagenodus sp. due to its incompleteness. In the literature, Montceau-les-Mines is...
Daniel Snitting - One of the best experts on this subject based on the ideXlab platform.
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a new tristichopterid Sarcopterygii tetrapodomorpha from the upper famennian evieux formation upper devonian of belgium
Palaeontology, 2009Co-Authors: Gaël Clément, Daniel Snitting, Per E AhlbergAbstract:Additional material of a large specimen of tristichopterid fish from the Upper Famennian Evieux Formation of Belgium is described. This large fish was previously assigned to Tristichopteridae g ...
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a redescription of the anatomy of the late devonian spodichthys buetleri jarvik 1985 Sarcopterygii tetrapodomorpha from east greenland
Journal of Vertebrate Paleontology, 2008Co-Authors: Daniel SnittingAbstract:The tetrapodomorph fish Spodichthys buetleri from the Upper Devonian of East Greenland is redescribed from computed tomography scans of material originally studied by Erik Jarvik. A wealth of new a ...
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morphology taxonomy and interrelationships of tristichopterid fishes Sarcopterygii tetrapodomorpha
2008Co-Authors: Daniel SnittingAbstract:Tristichopterids (Sarcopterygii, Tetrapodomorpha) form a monophyletic group of exclusively Devonian fishes. This thesis consists of descriptions of new material of tristichopterids and closely rela ...
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a redescription of the anatomy of spodichthys buetleri jarvik 1985 Sarcopterygii tetrapodomorpha
Ichthyolith Issues Special Publication 10, 2007Co-Authors: Daniel SnittingAbstract:A redescription of the anatomy of Spodichthys buetleri Jarvik, 1985 (Sarcopterygii, Tetrapodomorpha)
Per E Ahlberg - One of the best experts on this subject based on the ideXlab platform.
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the first virtual cranial endocast of a lungfish Sarcopterygii dipnoi
PLOS ONE, 2014Co-Authors: Alice M. Clement, Per E AhlbergAbstract:Lungfish, or dipnoans, have a history spanning over 400 million years and are the closest living sister taxon to the tetrapods. Most Devonian lungfish had heavily ossified endoskeletons, whereas most Mesozoic and Cenozoic lungfish had largely cartilaginous endoskeletons and are usually known only from isolated tooth plates or disarticulated bone fragments. There is thus a substantial temporal and evolutionary gap in our understanding of lungfish endoskeletal morphology, between the diverse and highly variable Devonian forms on the one hand and the three extant genera on the other. Here we present a virtual cranial endocast of Rhinodipterus kimberleyensis, from the Late Devonian Gogo Formation of Australia, one of the most derived fossil dipnoans with a well-ossified braincase. This endocast, generated from a Computed Microtomography (µCT) scan of the skull, is the first virtual endocast of any lungfish published, and only the third fossil dipnoan endocast to be illustrated in its entirety. Key features include long olfactory canals, a telencephalic cavity with a moderate degree of ventral expansion, large suparaotic cavities, and moderately enlarged utricular recesses. It has numerous similarities to the endocasts of Chirodipterus wildungensis and Griphognathus whitei, and to a lesser degree to 'Chirodipterus' australis and Dipnorhynchus sussmilchi. Among extant lungfish, it consistently resembles Neoceratodus more closely than Lepidosiren and Protopterus. Several trends in the evolution of the brains and labyrinth regions in dipnoans, such as the expansions of the utricular recess and telencephalic regions over time, are identified and discussed.
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first record of porolepis Sarcopterygii porolepiformes from eastern gondwana
Canadian Journal of Earth Sciences, 2013Co-Authors: Zerina Johanson, Per E Ahlberg, Alex RitchieAbstract:Porolepiformes (Sarcopterygii) are poorly represented in the Devonian of Australia and eastern Gondwana as a whole. New cosmine-covered lower jaws from the Mulga Downs Group, western New South Wales (?Pragian–Emsian or Eifelian), represent the first occurrence of Porolepis in Australia, a genus formerly known exclusively from the Northern Hemisphere. This material is assigned to the new species Porolepis foxi . The wide distribution of Porolepis , demonstrated by its occurrence in New South Wales, Europe, and Spitsbergen, contrasts with the generally high endemicity of the faunas in which it is present.
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a new tristichopterid Sarcopterygii tetrapodomorpha from the upper famennian evieux formation upper devonian of belgium
Palaeontology, 2009Co-Authors: Gaël Clément, Daniel Snitting, Per E AhlbergAbstract:Additional material of a large specimen of tristichopterid fish from the Upper Famennian Evieux Formation of Belgium is described. This large fish was previously assigned to Tristichopteridae g ...
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Fish fingers: digit homologues in sarcopterygian fish fins
Journal of Experimental Zoology, 2007Co-Authors: Zerina Johanson, Jean M.p. Joss, Catherine A. Boisvert, Rolf Ericsson, Margareta Sutija, Per E AhlbergAbstract:A defining feature of tetrapod evolutionary origins is the transition from fish fins to tetrapod limbs. A major change during this transition is the appearance of the autopod (hands, feet), which comprises two distinct regions, the wrist/ankle and the digits. When the autopod first appeared in Late Devonian fossil tetrapods, it was incomplete: digits evolved before the full complement of wrist/ankle bones. Early tetrapod wrists/ankles, including those with a full complement of bones, also show a sharp pattern discontinuity between proximal elements and distal elements. This suggests the presence of a discontinuity in the proximal-distal sequence of development. Such a discontinuity occurs in living urodeles, where digits form before completion of the wrist/ankle, implying developmental independence of the digits from wrist/ankle elements. We have observed comparable independent development of pectoral fin radials in the lungfish Neoceratodus (Osteichthyes: Sarcopterygii), relative to homologues of the tetrapod limb and proximal wrist elements in the main fin axis. Moreover, in the Neoceratodus fin, expression of Hoxd13 closely matches late expression patterns observed in the tetrapod autopod. This evidence suggests that Neoceratodus fin radials and tetrapod digits may be patterned by shared mechanisms distinct from those patterning the proximal fin/limb elements, and in that sense are homologous. The presence of independently developing radials in the distal part of the pectoral (and pelvic) fin may be a general feature of the Sarcopterygii. J. Exp. Zool. (Mol. Dev. Evol.) 308B:757–768, 2007. © 2007 Wiley-Liss, Inc.
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the late devonian lungfish soederberghia Sarcopterygii dipnoi from australia and north america and its biogeographical implications
Journal of Vertebrate Paleontology, 2001Co-Authors: Per E Ahlberg, Zerina Johanson, Edward B DaeschlerAbstract:Abstract A new species of rhynchodipterid lungfish, Soederberghia simpsoni, sp. nov., is described on the basis of a complete skull roof, and an incomplete but articulated head plus body, from the Upper Devonian Mandagery Sandstone near Canowindra, New South Wales (NSW, Fig. 1A,), Australia. It is compared with Soederberghia material from the upper part of the Catskill Formation, Pennsylvania (Fig. 1B), and the Cloghnan Shale at Jemalong near Forbes, NSW, Australia. The Catskill and Cloghnan Shale material, consisting of two incomplete skull roofs, appears to be conspecific with the type species, Soederberghia groenlandica from the Famennian Remigolepis Series of Greenland. This is congruent with a recent suggestion that the Mandagery Sandstone is late Frasnian in age, whereas the upper Catskill Formation and Cloghnan Shale are Famennian. At the Famennian localities, Soederberghia is associated with tetrapods. Articulated postcranial material of Soederberghia, including the pectoral girdle, cranial and pl...
Zerina Johanson - One of the best experts on this subject based on the ideXlab platform.
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first record of porolepis Sarcopterygii porolepiformes from eastern gondwana
Canadian Journal of Earth Sciences, 2013Co-Authors: Zerina Johanson, Per E Ahlberg, Alex RitchieAbstract:Porolepiformes (Sarcopterygii) are poorly represented in the Devonian of Australia and eastern Gondwana as a whole. New cosmine-covered lower jaws from the Mulga Downs Group, western New South Wales (?Pragian–Emsian or Eifelian), represent the first occurrence of Porolepis in Australia, a genus formerly known exclusively from the Northern Hemisphere. This material is assigned to the new species Porolepis foxi . The wide distribution of Porolepis , demonstrated by its occurrence in New South Wales, Europe, and Spitsbergen, contrasts with the generally high endemicity of the faunas in which it is present.
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Fish fingers: digit homologues in sarcopterygian fish fins
Journal of Experimental Zoology, 2007Co-Authors: Zerina Johanson, Jean M.p. Joss, Catherine A. Boisvert, Rolf Ericsson, Margareta Sutija, Per E AhlbergAbstract:A defining feature of tetrapod evolutionary origins is the transition from fish fins to tetrapod limbs. A major change during this transition is the appearance of the autopod (hands, feet), which comprises two distinct regions, the wrist/ankle and the digits. When the autopod first appeared in Late Devonian fossil tetrapods, it was incomplete: digits evolved before the full complement of wrist/ankle bones. Early tetrapod wrists/ankles, including those with a full complement of bones, also show a sharp pattern discontinuity between proximal elements and distal elements. This suggests the presence of a discontinuity in the proximal-distal sequence of development. Such a discontinuity occurs in living urodeles, where digits form before completion of the wrist/ankle, implying developmental independence of the digits from wrist/ankle elements. We have observed comparable independent development of pectoral fin radials in the lungfish Neoceratodus (Osteichthyes: Sarcopterygii), relative to homologues of the tetrapod limb and proximal wrist elements in the main fin axis. Moreover, in the Neoceratodus fin, expression of Hoxd13 closely matches late expression patterns observed in the tetrapod autopod. This evidence suggests that Neoceratodus fin radials and tetrapod digits may be patterned by shared mechanisms distinct from those patterning the proximal fin/limb elements, and in that sense are homologous. The presence of independently developing radials in the distal part of the pectoral (and pelvic) fin may be a general feature of the Sarcopterygii. J. Exp. Zool. (Mol. Dev. Evol.) 308B:757–768, 2007. © 2007 Wiley-Liss, Inc.
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new onychodontiform osteichthyes Sarcopterygii from the lower devonian of victoria australia
Journal of Paleontology, 2007Co-Authors: Zerina Johanson, Philippe Janvier, John A Long, John A Talent, James W WarrenAbstract:Abstract The Onychodontiformes is a poorly known sarcopterygian fish group, with four genera currently described, predominantly from the Middle-Late Devonian. A new onychodont, Bukkanodus jesseni n. gen. and sp., from the Fairy Formation, Victoria, Australia, is of Early Devonian (mid-late Pragian) age, representing one of the oldest known occurrences of this group. Other Pragian onychodonts are represented by a single lower jaw from China, while older occurrences (Lochkovian) include a lower jaw also from China and isolated teeth from Nevada. The Australian material, though disarticulated, includes skull, jaw, and palatal and dental specimens. These specimens share characteristics with younger onychodont taxa, including a laterally compressed tooth whorl with main and accessory rows containing an equal number of teeth, an anteriorly arched shape of the premaxilla, a lateral rostral bone participating in the orbital margin, parietals separated in the midline by small bones, the insertion of the basispheno...
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strepsodus rhizodontida Sarcopterygii pectoral elements from the lower carboniferous ducabrook formation queensland australia
Journal of Vertebrate Paleontology, 2005Co-Authors: Kate Parker, Anne Warren, Zerina JohansonAbstract:New rhizodontid pectoral girdle and fin material from Queensland, Australia (Middle Paddock site, Ducabrook Formation, Lower Carboniferous) includes cleithra, clavicles, anocleithra, scapulocoracoids, a humerus, an ulna, and a probable ulnare. The morphology of the humerus, including an enlarged pectoral process and a ball-shaped caput humeri, is comparable to humeri assigned to Strepsodus. This confirms the previous assignment of cleithra and clavicles from Middle Paddock to this genus and thus the presence of Strepsodus in eastern Gondwana. Based on examination of the new pectoral elements from the Ducabrook Formation, we provide new characters for an emended diagnosis of Strepsodus.
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Placoderm branchial and hypobranchial muscles and origins in jawed vertebrates
Journal of Vertebrate Paleontology, 2003Co-Authors: Zerina JohansonAbstract:Abstract Muscle morphology in the Placodermi can be inferred by comparison to extant gnathostomes (Chondrichthyes (Actinopterygii + Sarcopterygii)). Examination of the chondrichthyan hypobranchial musculature suggested a comparable musculature for placoderms, including the coracomandibularis and coracohyoideus, acting separately to depress the mandible and hyoid arch. In sharks, this was associated with the absence of a mandibulohyoid ligament functioning in mandible depression, a characteristic feature of actinopterygians and sarcopterygians. Additionally, the coracobranchiales muscles depress the chondrichthyan ventral gill arches, the clavobranchiales being the corresponding muscles in actinopterygians and sarcopterygians. These muscles and ligaments are not preserved in placoderms, but their attachments can be compared to those of extant gnathostomes. On the placoderm lower jaw, attachment surfaces for the mandibulohyoid ligament are only present in derived taxa and position relative to the jaw joint ...
Philippe Janvier - One of the best experts on this subject based on the ideXlab platform.
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further evidence for the presence of holoptychiid porolepiforms Sarcopterygii dipnomorpha from the frasnian of colombia
Comptes Rendus Palevol, 2014Co-Authors: Jorge Mondejarfernandez, Philippe JanvierAbstract:Abstract The Devonian (Frasnian) of Colombia has provided important information on the taxonomical diversity and palaeobiogeographic relationships of the Late Devonian marginal marine vertebrate faunas of South America (northwestern margin of Gondwana). This fauna is mostly composed of Gondwanan endemics, but includes two taxa also known in Euramerica: the antiarchan placoderm Asterolepis and the porolepiform sarcopterygian Holoptychius. The occurrence of holoptychiid porolepiforms in Colombia was previously suggested based solely on the presence of scales attributed to Holoptychius, although with caution. Here, we describe further holoptychiid remains that include a large isolated tooth with dendrodont microstructure, typical of porolepiforms, and additional Holoptychius scales. These new findings increase the record of holoptychiid porolepiform occurrences in Gondwana and suggest that dispersion of fish faunas between Euramerica and Gondwana by the beginning of the Late Devonian was possible through South America.
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the giant cretaceous coelacanth actinistia Sarcopterygii megalocoelacanthus dobiei schwimmer stewart williams 1994 and its bearing on latimerioidei interrelationships
PLOS ONE, 2012Co-Authors: Hugo Dutel, Philippe Janvier, Marc Herbin, John G Maisey, David R Schwimmer, Gaël ClémentAbstract:We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.
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The Giant Cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and Its Bearing on Latimerioidei Interrelationships
PLOS ONE, 2012Co-Authors: Hugo Dutel, Philippe Janvier, Marc Herbin, John G Maisey, David R Schwimmer, Gaël ClémentAbstract:We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.
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new onychodontiform osteichthyes Sarcopterygii from the lower devonian of victoria australia
Journal of Paleontology, 2007Co-Authors: Zerina Johanson, Philippe Janvier, John A Long, John A Talent, James W WarrenAbstract:Abstract The Onychodontiformes is a poorly known sarcopterygian fish group, with four genera currently described, predominantly from the Middle-Late Devonian. A new onychodont, Bukkanodus jesseni n. gen. and sp., from the Fairy Formation, Victoria, Australia, is of Early Devonian (mid-late Pragian) age, representing one of the oldest known occurrences of this group. Other Pragian onychodonts are represented by a single lower jaw from China, while older occurrences (Lochkovian) include a lower jaw also from China and isolated teeth from Nevada. The Australian material, though disarticulated, includes skull, jaw, and palatal and dental specimens. These specimens share characteristics with younger onychodont taxa, including a laterally compressed tooth whorl with main and accessory rows containing an equal number of teeth, an anteriorly arched shape of the premaxilla, a lateral rostral bone participating in the orbital margin, parietals separated in the midline by small bones, the insertion of the basispheno...
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a primitive megalichthyid fi sh Sarcopterygii tetrapodomorpha from the upper devonian of turkey and its biogeographical implications
Geodiversitas, 2007Co-Authors: Philippe Janvier, Gaël Clément, Richard CloutierAbstract:Th e vertebrate fauna of the red sandstone of Pamucak-Sapan Dere Unit of the Upper Antalya Nappe (Frasnian?, Turkey) is reviewed on the basis of new material. Th e association of the phyllolepid Placolepis with the arthrodire Holonema in this fauna strongly suggests a Frasnian age or, at any rate, older than the Famennian. Th e unique osteolepiform sarcopterygian of this fauna is here described in detail and referred to Sengoerichthys ottoman n. gen., n. sp., which is considered as the most generalized megalichthyid known to date.
