Browsing by Author "Pritchard, Adam C., 1987-"
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Item High resolution images for 'Postcranial osteology of Azendohsaurus madagaskarensis (?Middle to Upper Triassic, Isalo Group, Madagascar) and its systematic position among stem archosaur reptiles. (Bulletin of the American Museum of Natural History, no. 398)'(2015) Nesbitt, Sterling J.; Flynn, John J. (John Joseph), 1955-; Pritchard, Adam C., 1987-; Parrish, J. Michael, 1953-; Ranivoharimanana, Lovasoa.; Wyss, André R.High resolution images for 'Postcranial osteology of Azendohsaurus madagaskarensis (?Middle to Upper Triassic, Isalo Group, Madagascar) and its systematic position among stem archosaur reptiles. (Bulletin of the American Museum of Natural History, no. 398)' - http://hdl.handle.net/2246/6624Item Osteology of a North American goniopholidid (Eutretauranosuchus delfsi) and palate evolution in Neosuchia. (American Museum novitates, no. 3783)(American Museum of Natural History., 2013-10-23) Pritchard, Adam C., 1987-; Turner, Alan H. (Alan Hamilton); Allen, Eric R. (Eric Randall); Norell, Mark.The goniopholidid Eutretauranosuchus delfsi is currently known from two skulls from the Late Jurassic Morrison Formation of Colorado. Here we present a detailed osteology for a third Eutretauranosuchus delfsi specimen (AMNH FARB 570), consisting of a skull and fragmentary postcranium from Bone Cabin Quarry, Wyoming (Morrison Formation). Additional preparation, computed tomography (CT), and three-dimensional processing of CT images reveal matrix-covered structures on AMNH FARB 570, provide new information on goniopholidid cranial anatomy, and allow for the first description of an articulated North American goniopholidid braincase. These new data, along with restudy of the palatal anatomy in Eutretauranosuchus, provide valuable insight into the phylogenetic history of goniopholidid crocodyliforms. The skull of AMNH FARB 570 is extremely similar to other specimens of E. delfsi and Amphicotylus spp., especially in details of the architecture of the palate. In these Morrison Formation goniopholidids the secondary palate is incomplete such that the nasopharyngeal passage has no ventral floor. Additionally, there is a complex septum, constructed from the vomers and pterygoid, which extends ventrally near to the plane of the secondary palate. Characters diagnosing Eutretauranosuchus delfsi include: (1) an elongate, platyrostral skull; (2) a prominent depression on the posterolateral surface of the alveolar process of the maxilla; (3) minimal lateral undulation of the maxillary tooth row; (4) broadening of the nasals anterior to the prefrontals; (5) nasals that do not contact external nares; (6) a broad, flat interfenestral bar with raised rims along the supratemporal fenestrae; (7) a nasopharyngeal septum formed from diverging vomeral processes anteriorly and a midline pterygoid process posteriorly (also in Amphicotylus lucasii, AMNH FARB 5782); and (8) a vomeral septal complex that forms an X shape in cross section. Based on a revised phylogenetic analysis of 88 crocodylomorph taxa, a novel phylogenetic hypothesis is proposed in which a clade of Calsoyasuchus + Sunosuchus is sister to a clade of Goniopholis baryglyphaeus + (Goniopholis simus + (Amphicotylus lucasii + Eutretauranosuchus delfsi)). Examination of secondary palate characters in Goniopholididae suggests that this group "experimented" with changes to the bony secondary palate a number of times, resulting in morphologies not seen other mesoeucrocodylian clades.Item Postcranial osteology of Azendohsaurus madagaskarensis (?Middle to Upper Triassic, Isalo Group, Madagascar) and its systematic position among stem archosaur reptiles. (Bulletin of the American Museum of Natural History, no. 398)(American Museum of Natural History., 2015-12-07) Nesbitt, Sterling J.; Flynn, John J. (John Joseph), 1955-; Pritchard, Adam C., 1987-; Parrish, J. Michael, 1953-; Ranivoharimanana, Lovasoa.; Wyss, André R.During the Triassic, archosauromorphs became one of the first groups of diapsid reptiles to diversify in terms of body size and morphological disparity in both terrestrial and marine ecosystems across Pangaea. This seemingly rapid divergence, and the numerous unique body plans stemming from it, concomitantly has confounded reconstructions of archosauromorph relationships. Teasing apart homology from homoplasy of anatomical characters in this broad suite of body types remains an enormous challenge with the current sample of taxa. Here, we present the postcranial anatomy of Azendohsaurus madagaskarensis, an early archosauromorph from ?Middle to Upper Triassic strata of Madagascar. Azendohsaurus madagaskarensis is known from nearly the entire skeleton in an ontogenetically variable sample. The holotype locality consists of a monotypic bone bed; preservation ranges from complete but disarticulated bones to articulated sections of the skeleton. Azendohsaurus madagaskarensis embodies an aberrant constellation of archosauromorph features, including an elongated neck, a short, stocky tail, robust limbs, and unexpectedly short digits terminating in large recurved unguals on the manus and pes. Together with the cranium, the postcrania reveal A. madagaskarensis to be another representative of a growing coterie of highly apomorphic and bizarre Triassic archosauromorphs. At the same time, recovery and description of the full anatomy of A. madagaskarensis helps to identify a monophyletic grouping of specialized taxa that includes the North American Late Triassic-aged archosauromorphs Trilophosaurus, Spinosuchus, and Teraterpeton, Indian Pamelaria, and Moroccan Azendohsaurus laaroussii. Moreover, information derived from the skeleton of A. madagaskarensis solidifies the systematic position of these taxa among other archosauromorphs. Using the most comprehensively sampled phylogenetic analysis of early archosauromorphs, we found the clade encompassing the aforementioned taxa as the nearest outgroup of Prolacerta broomi + Archosauriformes. The newly recognized clade containing Azendohsaurus, Trilophosaurus, Spinosuchus, Pamelaria, and Teraterpeton demonstrates high morphological disparity even within a closely related group of archosauromorphs, underscores the polyphyly of protorosaurs (5 prolacertiforms), and suggests that most major divergences within this group occurred in the Triassic. Furthermore, our results indicate that craniodental character states ascribed to a herbivorous diet were much more pervasive across Triassic Archosauromorpha than previously conjectured.