THE TEMPORAL REGION OF THE FIRST AQUATIC CROCODYLOMORPHS AND A COMPARISON WITH EXTANT CROCODYLIANS

FERNANDEZ BLANCO, MARÍA VICTORIA; PASCAL ABEL; MICHELA M. JOHNSON; FRANZISKA ZEPF; BONA, PAULA; INGMAR WERNEBURG

Cairns, QLD

Congreso; 13th International Congress of Vertebrate Morphology; 2023

International Society of Vertebrate Morphologists

Approximately 100 million years before the emergence of extant crocodylians, thalattosuchian crocodylomorphs adapted to a pelagic life, with many taxa exhibiting several innovations in their skeleton unseen in other crocodylomorphs. In the semi-marine thalattosuchian subgroup Teleosauroidea, various anatomical differences from that of modern crocodylians can be observed. These not only include skull proportions, but also the enlarged supratemporal fenestrae (similar to other extinct marine reptiles), which contrasts with the reduced fenestrae of most living crocodylians. Additionally, living crocodylians exhibit a dietary shift during their ontogeny, accompanied by morphological changes such as the relative size of their temporal fenestrae and other cranial features. We hypothesize that such a dietary shift was also present in thalattosuchians but accompanied by a different anatomical transformation associated with a different jaw musculature arrangement. We perform a comprehensive geometric morphometric analysis on multiple skulls of the teleosauroid Macrospondylus bollensis from the Early Jurassic of Europe, in addition to some extant species of crocodylians. We quantify morphological differences between size classes, discuss how these dissimilarities may be related to jaw muscle action, and finally, compare this data with that obtained from modern crocodylians. This study will allow a better understanding of the the ecological, developmental, and evolutionary cranial changes among the crown-group and the oldest known aquatic crocodylomorphs.