Morfología neurocraneana del Teiidae (Squamata/Lacertilia) Callopistes cf. rionegrensis de la Formación Chichinales (Mioceno temprano), Provincia de Río Negro, Argentina

Abstract

The Teiidae family represents a lineage of lizards from the New World, with more than nine living genera that are distributed in the American continent and in the West Indies. The group's fossil record dates back to the Middle Triassic, with specimens found in America and Europe. The fossil record of skulls and particularly of neurocranial elements for the clade are extremely scarce, and the latter have been described in a small number of specimens worldwide. Only two taxa are registered in South America, Tupinambis uruguaianensis registered in the Touro Passo Formation, Uruguaiana, Río Grande do soul, Brazil and Callopistes rionegrensis from the Chichinales Formation, General Roca, Río Negro, Argentina, although the latter only preserves part of the parietal and the frontal.In the present Final Degree Project, the most complete fossil neurocranium of a scaly lizard from Argentina is described, assigned Callopistes cf. rionegrensis. The specimen (MPCN-PV754) corresponds to an isolated skull from the Chichinales Formation (early Miocene), in the “Paso Córdoba” National Protected Area, General Roca, Río Negro, Argentina. The material is an almost complete skull whose bony elements, immersed in a sandy matrix, keep their relative anatomical position. In order to avoid any damage to the specimen, no chemical and/or mechanical treatment was carried out. No-invasive computed microtomography was preferred to obtain a high-resolution, three-dimensional model of the skull and neurocranium. To compare the material with an extant representative of the genus, 3D modeling of the skull and neurocranium of the living species Callopistes maculatus was performed. During the comparison between both species, notable differences were observed in the morphology of the neurocrania located especially in: the development of the basal tubercles, the extension of the paraoccipital processes, the development of the ascending process of the supraoccipital, the projection of the basipterygoid processes and the shape of the foramen magnum. The relevance of this study focuses on generating valuable information about the neurocranial morphology of fossil tissues. Although a 3D reconstruction of the endocranial