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ABSTRACT: 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.
Naturwissenschaften 06/2011; 98(6):551-5. · 2.28 Impact Factor
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ABSTRACT: We have previously shown that intranasal (i.n.) administration of a single MHC class II-restricted HY peptide to female mice induces tolerance to up to five additional epitopes expressed on test male grafts, a phenomenon known as linked suppression. In this study, we investigated the molecular mechanisms involved both in the induction phase following peptide administration and during linked suppression after grafting. We report that following initial i.n. administration, peptide is widely disseminated and is presented by functionally immature dendritic cells. These fail to cause optimal stimulation of the responding HY-specific CD4(+) T cells that express genes characteristic of regulatory T cells. Following i.n. peptide plus LPS administration, causing immunization, HY-specific CD4(+) T cells express genes characteristic of activated T cells. We further find that following male skin grafting, HY-specific CD8(+) T cells from peptide-treated tolerant mice display both quantitative and qualitative differences compared with similar cells from untreated mice that reject their grafts. In tolerant mice there are fewer HY-specific CD8(+) cells and they express several genes characteristic of exhausted T cells. Furthermore, associated with specific chemokine receptor and integrin expression, HY-specific CD8(+) T cells show more limited migration from the graft draining lymph node into other tissues.
The Journal of Immunology 05/2011; 186(10):5719-28. · 5.79 Impact Factor
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ABSTRACT: The initial stages of evolution of Diapsida (the large clade that includes not only snakes, lizards, crocodiles and birds, but also dinosaurs and numerous other extinct taxa) is clouded by an exceedingly poor Palaeozoic fossil record. Previous studies had indicated a 38 Myr gap between the first appearance of the oldest diapsid clade (Araeoscelidia), ca 304 million years ago (Ma), and that of its sister group in the Middle Permian (ca 266 Ma). Two new reptile skulls from the Richards Spur locality, Lower Permian of Oklahoma, represent a new diapsid reptile: Orovenator mayorum n. gen. et sp. A phylogenetic analysis identifies O. mayorum as the oldest and most basal member of the araeoscelidian sister group. As Richards Spur has recently been dated to 289 Ma, the new diapsid neatly spans the above gap by appearing 15 Myr after the origin of Diapsida. The presence of O. mayorum at Richards Spur, which records a diverse upland fauna, suggests that initial stages in the evolution of non-araeoscelidian diapsids may have been tied to upland environments. This hypothesis is consonant with the overall scant record for non-araeoscelidian diapsids during the Permian Period, when the well-known terrestrial vertebrate communities are preserved almost exclusively in lowland deltaic, flood plain and lacustrine sedimentary rocks.
Proceedings of the Royal Society B: Biological Sciences 04/2011; 278(1725):3731-7. · 5.41 Impact Factor
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ABSTRACT: Inference of feeding preferences in fossil terrestrial vertebrates (tetrapods) has been drawn predominantly from craniodental morphology, and less so from fossil specimens preserving conclusive evidence of diet in the form of oral and/or gut contents. Recently, the pivotal role of insectivory in tetrapod evolution was emphasized by the identification of putative insectivores as the closest relatives of the oldest known herbivorous amniotes. We provide the first compelling evidence for insectivory among early tetrapods on the basis of two 280-million-year-old (late Palaeozoic) fossil specimens of a new species of acleistorhinid parareptile with preserved arthropod cuticle on their toothed palates. Their dental morphology, consisting of homodont marginal dentition with cutting edges and slightly recurved tips, is consistent with an insectivorous diet. The intimate association of arthropod cuticle with the oral region of two small reptiles, from a rich fossil locality that has otherwise not produced invertebrate remains, strongly supports the inference of insectivory in the reptiles. These fossils lend additional support to the hypothesis that the origins and earliest stages of higher vertebrate evolution are associated with relatively small terrestrial insectivores.
Biology letters 08/2009; 5(6):838-40. · 3.76 Impact Factor
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ABSTRACT: The partial skeleton of a small reptile, from the Middle Permian Tapinocephalus Assemblage Zone of South Africa, is described as a new parareptile. Australothyris smithi gen. et sp. nov. is diagnosed by contact between the postfrontal and the supratemporal, a relatively large pineal foramen, a small interpterygoid vacuity, the presence of teeth on the ventral surfaces of the basipterygoid processes, and several other autapomorphies. Phylogenetic analysis of an augmented data matrix from the literature positions A. smithi basally within Parareptilia, as the sister taxon of Ankyramorpha. Our results indicate that the presence of a lateral temporal fenestra is synapomorphic for procolophonomorphs (as regarded in this paper) and that this structure was variously modified in procolophonians. Australothyris smithi is the phylogenetically youngest member of a grade of Gondwanan parareptiles that includes mesosaurids and millerosaurs, a topology intimating that parareptiles diversified first in Gondwana and then dispersed into Laurasia. This biogeographic scenario is at odds with observations that the bolosaurids of Laurasia predate mesosaurids and other Gondwanan parareptiles by approximately 15 million years.Le squelette partiel d'un petit reptile provenant de la zone de l'assemblage de Tapinocephalus, du Permien moyen d'Afrique du Sud, est décrit comme étant un nouveau parareptile. Le diagnostic d'Australothyris smithi gen. et sp. nov. repose sur le contact entre les os postfrontal et supratemporal, un foramen pinéal relativement imposant, une petite vacuité interptérygoïde, la présence de dents sur les surfaces ventrales des processus basiptérygoïdes ainsi que plusieurs autres autapomorphies. L'analyse phylogénétique d'une matrice complète des données tirées de la documentation place A. smithi en position basale au sein des Parareptilia, comme taxon frère des Ankyramorpha. Les résultats de l'étude indiquent que la présence d'une fenêtre temporale latérale est synapomorphique pour les procolophonomorphes (comme les définit le présent article) et que, parmi les procolophoniens, cette structure a subi diverses modifications. Du point de vue phylogénétique, Australothyris smithi est le plus jeune membre d'un grade de parareptiles gondwaniens qui comprend les mésosauridés et les millérosaures, une topologie qui porte à croire que les parareptiles se sont d'abord diversifiés au Gondwana pour ensuite se disperser en Laurasie. Ce scénario biogéographique va à l'encontre d'observations voulant que les bolosauridés de la Laurasie aient vécu environ 15 millions d'années avant les mésosauridés et autres parareptiles gondwaniens.
Canadian Journal of Earth Sciences 12/2008; 46(1):9-20. · 1.12 Impact Factor
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ABSTRACT: The cranial skeleton of the large captorhinid reptile Labidosaurus hamatus, known only from the Lower Permian of Texas, is described on the basis of new, undescribed specimens. Labidosaurus is distinguished from other captorhinids by the more extreme sloping of the ventral (alveolar) margin of the premaxilla, a low dorsum sellae of the parabasisphenoid, a reduced prootic, a narrow stapes, and a relatively small foramen intermandibularis medius. Despite the presence of a single row of teeth in each jaw, the skull of Labidosaurus resembles most closely those of moradisaurines, the large multiple-tooth-rowed captorhinids of the latest Early and Middle Permian. A phylogenetic analysis confirms that the single-tooth-rowed L. hamatus is related most closely to moradisaurines within Captorhinidae, a relationship that supports the hypothesis of a diphyletic origin for multiple rows of marginal teeth in captorhinids (in the genus Captorhinus and in the clade Moradisaurinae). In view of the close relationship between L. hamatus and moradisaurines, which are regarded to have been herbivorous, L. hamatus is a critical taxon for studies of the evolution of herbivory in early tetrapods. L. hamatus shares several trademark features of herbivorous adaptation with moradisaurines, which suggest that this captorhinid species was omnivorous. As such, it represents a transitional taxon between faunivorous basal reptiles and the herbivorous moradisaurines. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 149, 237–262.
Zoological Journal of the Linnean Society 02/2007; 149(2):237 - 262. · 2.43 Impact Factor
