CRANIAL ANATOMY AND PALEOBIOLOGY OF ARARIPESUCHUS PATAGONICUS ORTEGA ET AL 2000 (CROCODYLIFORMES, URUGUAYSUCHIDAE) FROM THE CRETACEOUS OF PATAGONIA

BARRIOS, F.; BONA, P.; PAULINA CARABAJAL, A.; FERNANDEZ-DUMONT, M.L.; GASPARINI, Z.

Salta

Jornada; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2022

Universidad Nacional de Salta

Araripesuchus patagonicus was the first species of the Gondwanan Uruguaysuchidae (Crocodyliformes, Notosuchia), to be described in the Lower Cretaceous (Cenomanian, Candelero Formation) of Patagonia (Argentina). It is based on six likely juvenile associated specimens, housed at the Museo de la Universidad Nacional del Comahue, Paleontología Vertebrados, Neuquén (MUCPv 267, 268, 268b, 269, 270 and 283). They are represented by articulated skeletons that comprise cranial and postcranial elements. Although there is a lot of available anatomical information, the cranial anatomy of A. patagonicus was poorly explored, and many aspects of their braincase, neuroanatomy and paleobiology remain unknown. Based on CT scans and first hand observations, we described in detail the braincase and neuroanatomy of the MUCPv 267 and 269 specimens, with the aim of contribute to paleobiological interpretations of this species based on paleoneurological reconstructions. We identify several cranial osteological features, such as: ornamentation poorly marked; two palpebral bones (one anterior palpebral L-shaped and a second, posterior palpebral thinner, triangular, and smaller, that differs from that of the closely related peirosaurids); orbits relatively enlarged (probably related with the juvenile condition of the specimens); frontal bone with short cristae cranii and well marked oval depression for olfactory bulb (features shared with other terrestrial notosuchians such as Notosuchus, Yacarerani, Wargosuchus and different from semi-aquatic crocodylians); trigeminal foramen relatively small (as in other notosuchians, except some peirosaurids), supraoccipital exposed in the skull table (as some notosuchians); occiput divided by horizontal ridge (as all notosuchians) and with neurovascular foramina setting as peirosaurids (with carotid foramen dorsally adjacent to metotic foramen). The digital cranial endocast of A. patagonicus (MUCPv 269) has olfactory bulbs, cerebral hemispheres, optic lobes, and a relatively well developed flocculus of cerebellum. Inner ear morphology remains unknown.Comparisons between cranial endocast of the specimens MUCPv 269 and 267 indicate that the first is the youngest and shows an overall morphology similar to that of living young juvenile crocodylians. The conjunction of relatively enlarged orbits and optic lobes would be related to scotopic vision (under low light conditions), and based on the palpebral morphology, the relative development of olfactory bulbs and flocculus of the cerebellum, crepuscular or nocturnal habits can be inferred for A. patagonicus. In some living amniotes (such as mammals) these habits are related to gregariousnes and thermoregulation, and considering the arid paleoenviroment and taphonomic characteristics of A. patagonicus record, similar habits could be inferred for this species.