The braincase of a specimen of <Emphasis Type="Italic">Proterochampsa</Emphasis> Reig (Archosauriformes: Proterochampsidae) from the Late Triassic of Argentina |
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Authors: | María Jimena Trotteyn José Augusto Haro |
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Institution: | 1.Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET),Buenos Aires,Argentina;2.Instituto y Museo de Ciencias Naturales,Universidad Nacional de San Juan,San Juan Capital,Argentina;3.Centro de Investigaciones Paleobiológicas (CIPAL), Facultad de Ciencias Exactas, Físicas y Naturales,Universidad Nacional de Córdoba,Córdoba,Argentina |
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Abstract: | The proterochampsids are a Triassic group of superficially crocodile-like forms belonging to the Archosauriformes. In the
present contribution, we present new information regarding the braincase of the proterochampsid Proterochampsa Reig 1959, from the Ischigualasto Formation (Carnian) of Argentina, and discuss its phylogenetic considerations. Some unique neurocranial
features of Proterochampsa are described, including: the prominence and thickness of the V-shaped ridge that surrounds the basisphenoidal fossa; the
medially concave lateral arms of the same ridge; and the semilunar depression on the parabasisphenoid ventrolaterally exposed.
Other features are only shared with likely unrelated archosauriforms, including: the great lateral development of the basipterygoid
processes and caudal development of its distal end; an eight-shaped metotic foramen; laterally directed basipterygoid processes;
and rostral boundary of the basisphenoidal recess V-shaped. Proterochampsa differs in many other aspects from the archosauriform Chanaresuchus, including: a proportionally shorter basioccipital basal tubera; cultriform process ovoid in cross-section; longitudinal
sulcus dorsal to the basipterygoid process; deep basisphenoidal recess; and the absence of a prominent intertuberal plate.
In many braincase features, Proterochampsa is more similar to archosaurs than to Euparkeria, erythrosuchids and Proterosuchus. They include a reduced semilunar depression. A ventral border of the basioccipital forming a wide convexity and a dorsoventrally
thin paroccipital process likely represents a feature shared with Chanaresuchus, but not with Doswellia and other basal archosauriforms. |
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