Another paper from the upcoming volume on Triassic archosaurs.
Dalla Vecchia, F. 2013. Triassic Pterosaurs. From Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) 2013. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379, http://dx.doi.org/10.1144/SP379.14
Abstract - Pterosaurs are a clade of highly specialized, volant archosauromorphs recorded from the Upper Triassic to the uppermost Cretaceous. Problematic remains referred to the Pterosauria are reported from the Triassic of Europe and both North and South America, but unequivocal pterosaur specimens are only known from the Alps (Italy, Austria and Switzerland: Preondactylus buffarinii, Austriadactylus cristatus, Peteinosaurus zambellii, Eudimorphodon ranzii, Carniadactylus rosenfeldi, Caviramus schesaplanensis and Raeticodactylus filisurensis) and Greenland (‘Eudimorphodon’ cromptonellus). Pterosaurs are diagnosed mostly by features associated with the advent of powered flight. They are generally considered to be archosaurians more closely related to dinosaurs than to crocodilians, but non-archosaurian positions have also been proposed. There is a lack of general agreement about ingroup relationships, particularly among the basal pterosaurs. Triassic pterosaurs differ from other non-pterodactyloid pterosaurs in features of the dentition and caudal vertebral column. A ‘Big Bang’ model for their early history fits better with the fossil record: the earliest unequivocal pterosaurs show a sudden and geographically limited appearance in the fossil record, as well as a relatively high burst of diversity and considerable morphologic disparity. Absence of pterosaur remains from deposits where they are expected to be found suggests that they had not yet evolved in pre-Norian times.
Showing posts with label ornithodira. Show all posts
Showing posts with label ornithodira. Show all posts
Two New Triassic Archosaurian Taxa in the New Issue of Acta Palaeontologica Polonica
These two papers have been available for awhile as accepted manuscripts, but now they are officially out and freely downloadable.
Niedźwiedzki, G., Sulej, T., and J. Dzik. 2012. A large predatory archosaur from the Late Triassic of Poland. Acta Palaeontologica Polonica 57 (2): 267-276. doi: http://dx.doi.org/10.4202/app.2010.0045
Abstract - We describe a new large predatory archosaur, Smok wawelski gen. et sp. nov., from the latest Triassic (latest Norian–early Rhaetian; approximately 205–200 Ma) of Lisowice (Lipie Śląskie clay−pit) in southern Poland. The length of the reconstructed skeleton is 5–6 m and that of the skull 50–60 cm, making S. wawelski larger than any other known predatory archosaur from the Late Triassic and Early Jurassic of central Europe (including theropod dinosaurs and “rauisuchian” crurotarsans). The holotype braincase is associated with skull, pelvic and isolated limb−bones found in close proximity (within 30 m), and we regard them as belonging to the same individual. Large, apparently tridactyl tracks that occur in the same rock unit may have been left by animals of the same species. The highly autapomorphic braincase shows large attachment areas for hypertrophied protractor pterygoideus muscles on the lateral surface and a wide, funnel−like region between the basal tubera and basipterygoid processes on the ventral surface. The skeleton (cranial and postcranial) possesses some features similar to those in theropod dinosaurs and others to those in large crocodile−line archosaurs (“rauisuchians”), rendering phylogenetic placement of S. wawelski difficult at this time.
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Kammerer, C. F., Nesbitt, S. J., and N. H. Shubin. 2012. The first silesaurid dinosauriform from the Late Triassic of Morocco. Acta Palaeontologica Polonica 57 (2): 277-284 doi: http://dx.doi.org/10.4202/app.2011.0015
Abstract - Disarticulated material from the Late Triassic Timezgadiouine Formation in the Argana Basin of Morocco represents a new taxon of silesaurid dinosauromorph, Diodorus scytobrachion gen. et sp. nov. D. scytobrachion can be distinguished from other silesaurids by the presence of anteriorly−canted teeth that decrease in size towards the anterior end of the dentary and a distinct lateral ridge running parallel to the dentary alveolar margin. In a phylogenetic analysis, D. scytobrachion is recovered as the sister−taxon to the Brazilian Sacisaurus agudoensis, nested deep within Silesauridae. This new taxon provides further evidence of a near−cosmopolitan range for basal dinosauriforms in the Late Triassic and further demonstrates the disparity of dental morphologies within Silesauridae.
Niedźwiedzki, G., Sulej, T., and J. Dzik. 2012. A large predatory archosaur from the Late Triassic of Poland. Acta Palaeontologica Polonica 57 (2): 267-276. doi: http://dx.doi.org/10.4202/app.2010.0045
Abstract - We describe a new large predatory archosaur, Smok wawelski gen. et sp. nov., from the latest Triassic (latest Norian–early Rhaetian; approximately 205–200 Ma) of Lisowice (Lipie Śląskie clay−pit) in southern Poland. The length of the reconstructed skeleton is 5–6 m and that of the skull 50–60 cm, making S. wawelski larger than any other known predatory archosaur from the Late Triassic and Early Jurassic of central Europe (including theropod dinosaurs and “rauisuchian” crurotarsans). The holotype braincase is associated with skull, pelvic and isolated limb−bones found in close proximity (within 30 m), and we regard them as belonging to the same individual. Large, apparently tridactyl tracks that occur in the same rock unit may have been left by animals of the same species. The highly autapomorphic braincase shows large attachment areas for hypertrophied protractor pterygoideus muscles on the lateral surface and a wide, funnel−like region between the basal tubera and basipterygoid processes on the ventral surface. The skeleton (cranial and postcranial) possesses some features similar to those in theropod dinosaurs and others to those in large crocodile−line archosaurs (“rauisuchians”), rendering phylogenetic placement of S. wawelski difficult at this time.
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Kammerer, C. F., Nesbitt, S. J., and N. H. Shubin. 2012. The first silesaurid dinosauriform from the Late Triassic of Morocco. Acta Palaeontologica Polonica 57 (2): 277-284 doi: http://dx.doi.org/10.4202/app.2011.0015
Abstract - Disarticulated material from the Late Triassic Timezgadiouine Formation in the Argana Basin of Morocco represents a new taxon of silesaurid dinosauromorph, Diodorus scytobrachion gen. et sp. nov. D. scytobrachion can be distinguished from other silesaurids by the presence of anteriorly−canted teeth that decrease in size towards the anterior end of the dentary and a distinct lateral ridge running parallel to the dentary alveolar margin. In a phylogenetic analysis, D. scytobrachion is recovered as the sister−taxon to the Brazilian Sacisaurus agudoensis, nested deep within Silesauridae. This new taxon provides further evidence of a near−cosmopolitan range for basal dinosauriforms in the Late Triassic and further demonstrates the disparity of dental morphologies within Silesauridae.
Evolution of Morphological Disparity in Pterosaurs
Prentice, K. C., Ruta, M. and M. J. Benton. 2011. Evolution of morphological disparity in pterosaurs. Journal of Systematic Palaeontology DOI:10.1080/14772019.2011.565081
Abstract - Pterosaurs were important flying vertebrates for most of the Mesozoic, from the Late Triassic to the end of the Cretaceous (225–65 Ma). They varied enormously through time in overall size (with wing spans from about 250 mm to about 12 m), and in features of their cranial and postcranial skeletons. Comparisons of disparity based on discrete cladistic characters show that the basal paraphyletic rhamphorhynchoids (Triassic–Early Cretaceous) occupied a distinct, and relatively small, region of morphospace compared to the derived pterodactyloids (Late Jurassic–Late Cretaceous). This separation is unexpected, especially in view of common constraints on anatomy caused by the requirements of flight. Pterodactyloid disparity shifted through time, with different, small portions of morphospace occupied in the Late Jurassic and Late Cretaceous, and a much larger portion in the Early Cretaceous. This explosion in disparity after 100 Ma of evolution is matched by the highest diversity of the clade: evidently, pterosaurs express a rather ‘top heavy’ clade shape, and this is reflected in delayed morphological evolution, again an unexpected finding. The expansion of disparity among pterodactyloids was comparable across subclades: pairwise comparisons among the four pterodactyloid superfamilies show that, for the most part, these clades display significant morphological separation, except in the case of Dsungaripteroidea and Azhdarchoidea. Finally, there is no evidence that rhamphorhynchoids as a whole were outcompeted by pterodactyloids, or that pterosaurs were driven to extinction by the rise of birds.
Abstract - Pterosaurs were important flying vertebrates for most of the Mesozoic, from the Late Triassic to the end of the Cretaceous (225–65 Ma). They varied enormously through time in overall size (with wing spans from about 250 mm to about 12 m), and in features of their cranial and postcranial skeletons. Comparisons of disparity based on discrete cladistic characters show that the basal paraphyletic rhamphorhynchoids (Triassic–Early Cretaceous) occupied a distinct, and relatively small, region of morphospace compared to the derived pterodactyloids (Late Jurassic–Late Cretaceous). This separation is unexpected, especially in view of common constraints on anatomy caused by the requirements of flight. Pterodactyloid disparity shifted through time, with different, small portions of morphospace occupied in the Late Jurassic and Late Cretaceous, and a much larger portion in the Early Cretaceous. This explosion in disparity after 100 Ma of evolution is matched by the highest diversity of the clade: evidently, pterosaurs express a rather ‘top heavy’ clade shape, and this is reflected in delayed morphological evolution, again an unexpected finding. The expansion of disparity among pterodactyloids was comparable across subclades: pairwise comparisons among the four pterodactyloid superfamilies show that, for the most part, these clades display significant morphological separation, except in the case of Dsungaripteroidea and Azhdarchoidea. Finally, there is no evidence that rhamphorhynchoids as a whole were outcompeted by pterodactyloids, or that pterosaurs were driven to extinction by the rise of birds.
A Recent Mention of Two Possibly New Archosauriforms from the Middle Triassic of Germany
This very interesting article was recently brought to my attention. It mentions several possibly new archosauriforms from the Middle Triassic of Germany, including a proterochampsid and a small bipedal form that could be a basal ornithodiran.
http://www.swp.de/crailsheim/lokales/land/art5509,632515
http://www.swp.de/crailsheim/lokales/land/art5509,632515
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