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Jean-claude Rage - One of the best experts on this subject based on the ideXlab platform.
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The mid-Cretaceous snake Simoliophis rochebrunei Sauvage, 1880 (Squamata: Ophidia) from its type area (Charentes, southwestern France): Redescription, distribution, and palaeoecology
Cretaceous Research, 2016Co-Authors: Jean-claude Rage, Romain Vullo, Didier NéraudeauAbstract:Simoliophis rochebrunei is a snake restricted to the Cenomanian of southwestern Europe. It is the type species of the genus Simoliophis, the latter being the type genus of the Simoliophiidae, i.e. the family that is comprised of the marine hindlimbed snakes. The first descriptions of the species were insufficient and dealt only with mid-trunk vertebrae, whereas vertebrae from other parts of the vertebral column are markedly different from the latter. Paradoxically, species subsequently included in the genus are better known than the type species. In the present article, S. rochebrunei is described and diagnosed on the basis of material found recently in the type area (Charentes, southwestern France). Strong Pachyostosis affects the mid-trunk and the anterior portion of the posterior trunk region. A part of the vertebral column affected by Pachyostosis was more or less stiff. As with all pachyostotic squamates, S. rochebrunei was aquatic; it lived in shallow marine water, whose bottom was sandy, but it was also able to enter brackish environments. It was a slow swimmer capable of shallow, but long dives. The species may be used as a stratigraphic marker since it is restricted to the lower Cenomanian in the type area.
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an analysis of vertebral Pachyostosis in carentonosaurus mineaui mosasauroidea squamata from the cenomanian early late cretaceous of france with comments on its phylogenetic and functional significance
Journal of Vertebrate Paleontology, 2008Co-Authors: Alexandra Houssaye, Vivian Buffrénil, Jean-claude Rage, Nathalie BardetAbstract:Abstract The study of the so-called vertebral ‘Pachyostosis’ of Carentonosaurus mineaui, a plesiopedal mosasauroid sensu Bell & Polcyn from the Cenomanian (Late Cretaceous) of Charente-Maritime (Western France), has revealed that it actually corresponds to pachyosteosclerosis resulting from the combination of cortical hyperplasy with bone compaction due to an inhibition of chondroclastic and osteoclastic activities. This characteristic also occurs in other Cretaceous squamates such as Pachyvaranus crassispondylus and Simoliophis rochebrunei but it is absent in extant squamates. On the contrary, vertebrae of the latter display a very strong porosity due to intense bone remodelling during growth. The phylogenetic significance of pachyosteosclerosis in squamates is thus discussed. The peculiar structure of the vertebrae of Carentonosaurus may be regarded as the result of a heterochronic process, more specifically neoteny. Its association with an adaptation to shallow marine environment is consistent with the...
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An analysis of vertebral ‘Pachyostosis’ in Carentonosaurus mineaui (Mosasauroidea, Squamata) from the Cenomanian (early Late Cretaceous) of France, with comments on its phylogenetic and functional significance
Journal of Vertebrate Paleontology, 2008Co-Authors: Alexandra Houssaye, Vivian Buffrénil, Jean-claude Rage, Nathalie BardetAbstract:The study of the so-called vertebral 'Pachyostosis' of Carentonosaurus mineaui, a plesiopedal mosasauroid sensu Bell & Polcyn from the Cenomanian (Late Cretaceous) of Charente-Maritime (Western France), has revealed that it actually corresponds to pachyosteosclerosis resulting from the combination of cortical hyperplasy with bone compaction due to an inhibition of chondroclastic and osteoclastic activities. This characteristic also occurs in other Cretaceous squamates such as Pachyvaranus crassispondylus and Simoliophis rochebrunei but it is absent in extant squamates. On the contrary, vertebrae of the latter display a very strong porosity due to intense bone remodelling during growth. The phylogenetic significance of pachyosteosclerosis in squamates is thus discussed. The peculiar structure of the vertebrae of Carentonosaurus may be regarded as the result of a heterochronic process, more specifically neoteny. Its association with an adaptation to shallow marine environment is consistent with the inferred ecology of C. mineaui. Moreover, the histological features of the periosteal bone of Carentonosaurus vertebrae provide information about its growth pattern (asymmetry, rate, cyclicity) which may be compared to the ones of Pachyvaranus and Simoliophis.
Bruce S. Rubidge - One of the best experts on this subject based on the ideXlab platform.
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A juvenile specimen of Anteosaurus magnificus Watson, 1921 (Therapsida: Dinocephalia) from the South African Karoo, and its implications for understanding dinocephalian ontogeny
2017Co-Authors: Ashley Kruger, Bruce S. Rubidge, Fernando AbdalaAbstract:Anteosaurid dinocephalians were the apex terrestrial predators of the latter part of the Guadalupian (middle Permian) and became extinct at the end of that epoch. The group was relatively diverse in Russia, but represented by only two genera, Australosyodon and Anteosaurus, in the Karoo rocks of South Africa. A newly discovered skull of Anteosaurus magnificus from the Abrahamskraal Formation is unique among specimens of this taxon in having most of the individual cranial bones disarticulated, permitting accurate delimitation of cranial sutures for the first time. The relatively large orbits and unfused nature of the cranial sutures suggest juvenile status for the specimen. A computer-aided 3D reconstruction of the skull, and comparison with 11 additional individuals, enabled an allometric study of cranial growth in the species. Positive allometry for four of the measurements suggests rapid growth in the temporal region, and a significant difference in the development of the postorbital bar and suborbital bar between juveniles and adults. Pachyostosis was an important process in the cranial ontogeny of Anteosaurus, significantly modifying the skull roof of adults. This condition is more obvious in large individuals of the species, but it is recognized that variation may also be independent of growth and could be related to sexual dimorphism. Growth of the skull in Anteosaurus shows similar morphological trends to that of the Russian Titanophoneus and the Chinese Sinophoneus. The overall morphology of the juvenile Anteosaurus is clearly reminiscent of the adult skull of the Russian medium-sized Syodon, a condition that is more likely a result of similar skull sizes and the lack of strong Pachyostosis in adult Syodon.
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Distribution of characters linked to sexual display in non-mammalian therapsids.
2016Co-Authors: Julien Benoit, Paul R. Manger, Vincent Fernandez, Bruce S. RubidgeAbstract:Abbreviations: 0, character absent; 1, character present; 01, character documented in some taxa only; ♀♂, sexual dimorphism; B, cranial boss(es); C, large canine; OB, ossified braincase; P, skull Pachyostosis. Phylogeny and dates after [1, 19, 88, 92, 93].
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Cranial Bosses of Choerosaurus dejageri (Therapsida, Therocephalia): Earliest Evidence of Cranial Display Structures in Eutheriodonts
PLoS ONE, 2016Co-Authors: Julien Benoit, Paul R. Manger, Vincent Fernandez, Bruce S. RubidgeAbstract:Choerosaurus dejageri, a non-mammalian eutheriodont therapsid from the South African late Permian (similar to 259 Ma), has conspicuous hemispheric cranial bosses on the maxilla and the mandible. These bosses, the earliest of this nature in a eutheriodont, potentially make C. dejageri a key species for understanding the evolutionary origins of sexually selective behaviours (intraspecific competition, ritualized sexual and intimidation displays) associated with cranial outgrowths at the root of the clade that eventually led to extant mammals. Comparison with the tapinocephalid dinocephalian Moschops capensis, a therapsid in which head butting is strongly supported, shows that the delicate structure of the cranial bosses and the gracile structure of the skull of Choerosaurus would be more suitable for display and low energy combat than vigorous head butting. Thus, despite the fact that Choerosaurus is represented by only one skull (which makes it impossible to address the question of sexual dimorphism), its cranial bosses are better interpreted as structures involved in intraspecific selection, i.e. low-energy fighting or display. Display structures, such as enlarged canines and cranial bosses, are widespread among basal therapsid clades and are also present in the putative basal therapsid Tetraceratops insignis. This suggests that sexual selection may have played a more important role in the distant origin and evolution of mammals earlier than previously thought. Sexual selection may explain the subsequent independent evolution of cranial outgrowths and Pachyostosis in different therapsid lineages (Biarmosuchia, Dinocephalia, Gorgonopsia and Dicynodontia)
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A new mid-Permian burnetiamorph therapsid from the Main Karoo Basin of South Africa and a phylogenetic review of Burnetiamorpha
Institute of Paleobiology PAS, 2016Co-Authors: Michael O. Day, Bruce S. Rubidge, Fernando AbdalaAbstract:Discoveries of burnetiamorph therapsids in the last decade and a half have increased their known diversity but they remain a minor constituent of middle–late Permian tetrapod faunas. In the Main Karoo Basin of South Africa, from where the clade is traditionally best known, specimens have been reported from all of the Permian biozones except the Eodicynodon and Pristerognathus assemblage zones. Although the addition of new taxa has provided more evidence for burnetiamorph synapomorphies, phylogenetic hypotheses for the clade remain incongruent with their appearances in the stratigraphic column. Here we describe a new burnetiamorph specimen (BP/1/7098) from the Pristerognathus Assemblage Zone and review the phylogeny of the Burnetiamorpha through a comprehensive comparison of known material. Phylogenetic analysis suggests that BP/1/7098 is closely related to the Russian species Niuksenitia sukhonensis. Remarkably, the supposed mid-Permian burnetiids Bullacephalus and Pachydectes are not recovered as burnetiids and in most cases are not burnetiamorphs at all, instead representing an earlier-diverging clade of biarmosuchians that are characterised by their large size, dentigerous transverse process of the pterygoid and exclusion of the jugal from the lateral temporal fenestra. The evolution of Pachyostosis therefore appears to have occurred independently in these genera. The resulting biarmosuchian tree is significantly more congruent with the stratigraphic appearance of its constituent taxa than in previous phylogenetic hypotheses and, consequently, does not necessarily constrain the diversification of the Burnetiamorpha to before the Capitanian
Didier Néraudeau - One of the best experts on this subject based on the ideXlab platform.
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The mid-Cretaceous snake Simoliophis rochebrunei Sauvage, 1880 (Squamata: Ophidia) from its type area (Charentes, southwestern France): Redescription, distribution, and palaeoecology
Cretaceous Research, 2016Co-Authors: Jean-claude Rage, Romain Vullo, Didier NéraudeauAbstract:Simoliophis rochebrunei is a snake restricted to the Cenomanian of southwestern Europe. It is the type species of the genus Simoliophis, the latter being the type genus of the Simoliophiidae, i.e. the family that is comprised of the marine hindlimbed snakes. The first descriptions of the species were insufficient and dealt only with mid-trunk vertebrae, whereas vertebrae from other parts of the vertebral column are markedly different from the latter. Paradoxically, species subsequently included in the genus are better known than the type species. In the present article, S. rochebrunei is described and diagnosed on the basis of material found recently in the type area (Charentes, southwestern France). Strong Pachyostosis affects the mid-trunk and the anterior portion of the posterior trunk region. A part of the vertebral column affected by Pachyostosis was more or less stiff. As with all pachyostotic squamates, S. rochebrunei was aquatic; it lived in shallow marine water, whose bottom was sandy, but it was also able to enter brackish environments. It was a slow swimmer capable of shallow, but long dives. The species may be used as a stratigraphic marker since it is restricted to the lower Cenomanian in the type area.
Alexandra Houssaye - One of the best experts on this subject based on the ideXlab platform.
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Palaeoecological and morphofunctional interpretation of bone mass increase: an example in Late Cretaceous shallow marine squamates
Biological Reviews, 2013Co-Authors: Alexandra HoussayeAbstract:Bone mass increase (BMI; i.e. osteosclerosis with possible additional Pachyostosis) is characteristically displayed by many Late Cretaceous squamates that adapted to shallow marine environments-plesiopelvic mosasauroids, stem-ophidians and pachyophiids. A combined morphological and microanatomical analysis of vertebrae and, to a lesser extent, ribs of these fossil squamates provides new data about the distribution and variability of this osseous specialization in these taxa. Classical thin sections and third generation synchrotron microtomography and laminography were used for the microanatomical analysis. Following the explanation of the likely involvement of this specialization in the control of buoyancy, body trim and Carrier's constraint, new palaeoecological inferences and new hypotheses about the locomotor abilities and life environment of these organisms are produced. The taxa displaying BMI are considered to have undertaken long dives, hovering slowly and maintaining a horizontal trim, in shallow and protected water environments. Conversely, marine stem-ophidians deprived of this specialization are regarded as slow surface swimmers able to live in more open marine environments. This study highlights the importance of microanatomical data for palaeoecological studies. It also discusses the significance of the use of this specialization as a character in phylogenetic studies.
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A new aquatic pythonomorph (Reptilia, Squamata) from the Turonian (Late Cretaceous) of France
Comptes Rendus Palevol, 2009Co-Authors: Alexandra HoussayeAbstract:Abstract Disarticulated vertebrae from the Turonian of France display a distinctive suite of characters and probably represent a new pythonomorph. This taxon displays some degree of vertebral Pachyostosis s.s., often observed in varanoid squamates from the Cenomanian-Turonian interval of the ‘Mediterranean’ portion of the Tethys. The discovery of this new material highlights the importance of also describing possibly new taxa based on isolated remains.
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Pachyostosis in aquatic amniotes: a review
Integrative Zoology, 2009Co-Authors: Alexandra HoussayeAbstract:During the course of amniote evolution, numerous taxa secondarily adapted to an aquatic life. It appears that many of these taxa primitively display "Pachyostosis," an osseous specialization characterized by an increase in bone compactness and/or volume. The term "Pachyostosis" is used in morphological and histological descriptions to describe what in fact corresponds to different patterns. The aim of this paper is to present the current state of knowledge relative to this adaptation among aquatic amniotes. All the taxa that have returned to an aquatic environment are listed. Moreover, their degree of adaptation to the marine environment, their life environment, and the nature of their "pachyostotic" pattern, when present, are described. This inventory enables the evaluation of the current quality of the data relative to this specialization and provides an indication of the work that remains to be done. The functional consequences of "Pachyostosis," and notably its importance for buoyancy control in the context of hydrostatic regulation of the body trim, are discussed and opposed to the requirement of improved swimming abilities in the case of a hydrodynamic mode of trim regulation. Questions are posed about the significa-tion of the polymorphism displayed by this specialization between different taxa, different specimens of the same taxon and different bones of the same specimen, and the problem of quantification of Pachyostosis is discussed.
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an analysis of vertebral Pachyostosis in carentonosaurus mineaui mosasauroidea squamata from the cenomanian early late cretaceous of france with comments on its phylogenetic and functional significance
Journal of Vertebrate Paleontology, 2008Co-Authors: Alexandra Houssaye, Vivian Buffrénil, Jean-claude Rage, Nathalie BardetAbstract:Abstract The study of the so-called vertebral ‘Pachyostosis’ of Carentonosaurus mineaui, a plesiopedal mosasauroid sensu Bell & Polcyn from the Cenomanian (Late Cretaceous) of Charente-Maritime (Western France), has revealed that it actually corresponds to pachyosteosclerosis resulting from the combination of cortical hyperplasy with bone compaction due to an inhibition of chondroclastic and osteoclastic activities. This characteristic also occurs in other Cretaceous squamates such as Pachyvaranus crassispondylus and Simoliophis rochebrunei but it is absent in extant squamates. On the contrary, vertebrae of the latter display a very strong porosity due to intense bone remodelling during growth. The phylogenetic significance of pachyosteosclerosis in squamates is thus discussed. The peculiar structure of the vertebrae of Carentonosaurus may be regarded as the result of a heterochronic process, more specifically neoteny. Its association with an adaptation to shallow marine environment is consistent with the...
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A PRELIMINARY REPORT ON THE EVOLUTION OF THE VERTEBRAL MICROANATOMY WITHIN MOSASAUROIDS (REPTILIA, SQUAMATA)
2008Co-Authors: Alexandra HoussayeAbstract:The study of the vertebral microanatomy of three mosasauroids displaying distinct types of morphology (Haasiasaurus gittelmani, Tethysaurus nopcsai, and Mosasaurus hoffmanni), has revealed two kinds of bone microanatomical specializations within mosasauroids, depending on the taxa ecology. Plesiopedal and plesiopelvic mosasauroids (like Haasiasaurus) living in shallow marine environments display Pachyostosis s.l. facilitating hydrostatic regulation of the body trim. Conversely hydropedal and hydropelvic mosasauroids (like Mosasaurus) exhibit a reorganization of the vertebral bony tissues into a tight network of thin trabeculae likely conferring to the vertebrae the mechanical resistance required by faster swimmers relying on a hydrodynamic trim control in open-marine environments. The intermediary pattern observed in Tethysaurus suggests a progressive change in vertebral microanatomy reflecting the ecological shift that occurred during the evolution of the group.
F. Robin O'keefe - One of the best experts on this subject based on the ideXlab platform.
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A new skeleton of the cryptoclidid plesiosaur Tatenectes laramiensis reveals a novel body shape among plesiosaurs
Journal of Vertebrate Paleontology, 2011Co-Authors: F. Robin O'keefe, Hallie P. Street, Benjamin C. Wilhelm, Courtney D. Richards, Helen ZhuAbstract:ABSTRACT Current knowledge of plesiosaurs of clade Cryptoclidia is constrained by a lack of fossils from outside the Oxford Clay deposits of England. Recent fleldwork in the Sundance Formation of the Bighorn Basin, Wyoming, has resulted in the recovery of significant new fossils of cryptoclidid plesiosaurs, including the small-bodied form Tatenectes laramiensis. A new partial skeleton of this taxon is reported here; it is the most complete and best-preserved example of the taxon found to date, comprising a complete dorsal vertebral series, many ribs and gastralia, and a complete pelvic girdle. This skeleton illuminates several unique features of the taxon, including a novel pattern of midline Pachyostosis in the gastralia. In addition, a range of both axial and appendicular morphological features reveals that Tatenectes had a body shape unique among known plesiosaurs, characterized by extreme dorsoventral compression, and modest anteroposterior reduction. The combination of the new skeleton with informati...
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Evidence of Pachyostosis in the cryptocleidoid plesiosaur Tatenectes laramiensis from the Sundance Formation of Wyoming
Journal of Vertebrate Paleontology, 2010Co-Authors: Hallie P. Street, F. Robin O'keefeAbstract:In this paper we present evidence for Pachyostosis in the cryptocleidoid plesiosaur Tatenectes laramiensis Knight, 1900 (O\u27Keefe and Wahl, 2003a). Pachyostosis is not common in plesiosaurs and is particularly rare in non-pliosaurian plesiosaurs, although enlarged gastralia were first recognized in Tatenectes by Wahl (1999). This study aims to investigate the nature of the disproportionately large gastralia of Tatenectes m greater depth, based on new material. A recently discovered partial skeleton consisting of a dorsal vertebral series, ribs, gastralia, and a complete pelvic girdle was collected from the Jurassic-aged Sundance Formation of the Bighorn Basin in Wyoming during the summer of 2006. The gastralia of this specimen are disproportionately large considering the small size of the taxon (about 3 meters total length), and we therefore investigated the size of these elements quantitatively. Polished cross-sections were also prepared to explore the histology of the ribs and gastralia. The ribs of Tatenectes are not pachyostotic, whereas the gastralia exhibit a novel condition of Pachyostosis while lacking osteosclerosis
