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A new captorhinid reptile, Gansurhinus qingtoushanensis, gen. et sp. nov., from the Permian of China
Captorhinids, a clade of Paleozoic reptiles, are represented by a rich fossil record that extends from the Late Carboniferous into the Late Permian. Representatives of this clade dispersed from the equatorial regions of Laurasia into the temperate regions of Pangea during the Middle and Late Permian. This rich fossil record shows that there was an evolutionary trend from faunivorous to omnivorous and herbivorous feeding habits within this clade. The discovery of well-preserved captorhinid materials in the Middle Permian of China allows us to determine that the new taxon, Gansurhinus qingtoushanensis, gen. et sp. nov, is a member of Moradisaurinae, a clade of captorhinids with multiple tooth rows arranged in parallel. The presence of this moradisaurine in the Middle Permian of south central Asia leads us to suggest that paleogeographic changes during the Permian, with part of what is today China becoming a large peninsula of Pangea, allowed these early reptiles as well as other terrestrial vertebrates to extend their geographic ranges to this region of the Late Paleozoic supercontinent. 相似文献
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Recent histological studies have revealed a diversity of dental features in Permo-Carboniferous tetrapods. Here, we report on the occurrence of plicidentine (infolded dentine around the base of the tooth root) in Sphenacodontia, the first such documentation in Synapsida, the clade that includes mammals. Five taxa were examined histologically, Ianthodon schultzei, Sphenacodon ferocior, Dimetrodon limbatus, Dimetrodon grandis, and Secodontosaurus obtusidens. The tooth roots of Ianthodon possess multiple folds, which is generally viewed as the primitive condition for amniotes. Sphenacodon and D. limbatus have distinctive “four-leaf clover”-shaped roots in cross section, whereas Secodontosaurus has an elongate square shape with only subtle folding. The most derived and largest taxon examined in this study, D. grandis, has rounded roots in cross section and therefore no plicidentine. This pattern of a loss of plicidentine in sphenacodontids supports previous functional hypotheses of plicidentine, where teeth with shallow roots require folds to increase the area of attachment to the tooth-bearing element, whereas teeth with long roots do not. This pattern may also reflect differences in diet between co-occurring sphenacodontids as well as changes in feeding niche through time, specifically in the apex predator Dimetrodon. 相似文献
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A new bolosaurid parareptile, Belebey chengi sp. nov., is described from Dashankou, Gansu Province, China, a Middle Permian locality which is known mostly for its therapsid
fauna. The material consists of well-preserved mandibular and anterior skull remains and currently represents the largest
and latest surviving member of Bolosauridae. Phylogenetic analysis of bolosaurid interrelationships, the first analysis of
any clade of Early Permian parareptiles, indicates that the new taxon groups consistently with the other (Russian) members
of the genus Belebey, and forms the sister clade to the genus Bolosaurus from North America. The Early Permian Eudibamus cursoris from Germany falls into the basal most position within Bolosauridae. Our analysis also shows that the split between the main
bolosaurid lineages must have occurred near or before the Permo-Carboniferous boundary and that the paleo-equatorial region
of Laurasia probably served as the center of origination for these parareptiles. A similar pattern can be found in other clades
of Paleozoic amniotes, suggesting that this may be the general trend in early amniote evolution. 相似文献
4.
We report on a partial varanopid skull and mandible from the Pristerognathus Assemblage Zone of the Beaufort Group, in the South African Karoo Basin, which is probably latest Middle Permian (Capitanian)
in age. This mycterosaurine is not only the youngest known varanopid from the Southern Hemisphere, but it is also the youngest
known “pelycosaur” (i.e., non-therapsid synapsid). Like all other members of this clade of hypercarnivores, the teeth are
strongly flattened, recurved, and have finely serrated cutting edges. The anterior dentary teeth form a caniniform region,
and the splenial features a foramen intermandibularis oralis, the first ever to be described in a “pelycosaur.” The last varanopids
were the smallest carnivores of latest Middle Permian continental faunas. Occupation of the small carnivore guild appears
to have allowed varanopids to achieve a nearly cosmopolitan distribution throughout the Middle Permian, between the great
Early Permian radiation of basal synapsids and the spectacular diversification of therapsid synapsids in the Late Permian
and Early Triassic. 相似文献
5.
Cacops, one of the most distinctive Paleozoic amphibians, is part of a clade of dissorophoid temnospondyls that diversified in the
equatorial region of Pangea during the Late Carboniferous and Early Permian, persisting into the Late Permian in Central Russia
and China. Dissorophids were a successful group of fully terrestrial, often spectacularly armoured predators, the only amphibians
apparently able to coexist with amniotes when the latter started to dominate terrestrial ecosystems. In this paper, we describe
excellent new skulls from the Early Permian of Oklahoma attributed to Cacops, Cacops morrisi sp. nov. and provide for the first time detailed information about this iconic dissorophid. These specimens show anatomical
and ontogenetic features that will impact on future studies on the evolution of terrestriality in tetrapods. For example,
the large, posteriorly closed tympanic embayment has fine striations on an otherwise smooth surface, documenting the oldest
known clear evidence for the presence of a tympanic membrane in the fossil record, a structure that is used for hearing airborne
sound in extant tetrapods. The skull of C. morrisi also has several features associated with predatory behaviour, indicating that this dissorophid may have been one of the
top terrestrial predators of its time. 相似文献
6.
We report on dental and mandibular pathology in Labidosaurus hamatus, a 275 million-year-old terrestrial reptile from North America and associate it with bacterial infection in an organism that
is characterized by reduced tooth replacement. Analysis of the surface and internal mandibular structure using mechanical
and CT-scanning techniques permits the reconstruction of events that led to the pathology and the possible death of the individual.
The infection probably occurred as a result of prolonged exposure of the dental pulp cavity to oral bacteria, and this exposure
was caused by injury to the tooth in an animal that is characterized by reduced tooth replacement cycles. In these early reptiles,
the reduction in tooth replacement is an evolutionary innovation associated with strong implantation and increased oral processing.
The dental abscess observed in L. hamatus, the oldest known infection in a terrestrial vertebrate, provides clear evidence of the ancient association between terrestrial
vertebrates and their oral bacteria. 相似文献
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