Specialized Feeding Morphology in the Small Crocodyliform Scolomastaxand Implications for Woodbine Paleoecology

Abstract

The Arlington Archosaur Site (AAS) of Texas is a productive fossil locality found in the upper Lewisville Formation of the Woodbine Group (Cenomanian; Late Cretaceous). The AAS preserves a diverse flora and fauna from a lower delta plain, including at least 4‐5 taxa of crocodyliforms: Scolomastax, Deltasuchus, Terminonaris, Woodbinesuchus, and an undescribed eusuchian. In present‐day ecosystems, no more than two crocodyliform taxa are sympatric due to overlapping niche requirements. The greater diversity of sympatric crocodyliform taxa observed at the AAS and similar fossil localities is due to niche partitioning, which is achieved through increased morphological disparities in the feeding apparatus of sympatric taxa. Scolomastax is characterized by a shortened jaw, heterodont dentition, and enlarged coronoid‐like process, which is distinct from the generalist Deltasuchus and small‐prey specialists Terminonaris and Woodbinesuchus. Here, further work reconstructs the jaw musculature of Scolomastax and interprets its feeding ecology. Compared to other herbivorous and durophagus reptiles, Scolomastax possesses similar enlargement of the adductor musculature (particularly M. adductor mandibulae posterior and the M. pterygoideus muscles) and attachments that enhance their mechanical advantage, including some unique features not seen in any other taxa. These features confirm a specialized feeding morphology and further support an omnivorous diet reconstruction for Scolomastax. Such specialized feeding adaptations among crocodyliforms were not uncommon in the Cretaceous, where warmer global temperatures and equable conditions allowed Scolomastaxand similar small crocodyliforms to evolve specialized feeding morphologies and fill niches otherwise occupied by mammals in present‐day ecosystems. These conditions supported greater crocodyliform diversity at the AAS and similar ancient communities.