New cranial fossils of the Jurassic turtle Neusticemys neuquina and phylogenetic relationships of the only thalassochelydian known from the eastern Pacific

DE LA FUENTE, M. S.; FERNÁNDEZ, M.S.; GONZÁLEZ RUIZ, P.

JOURNAL OF PALEONTOLOGY

PALEONTOLOGICAL SOC INC

Año: 2019 p. 1 - 20

0022-3360

Neusticemys neuquina (Fernández and de la Fuente, 1988) is a turtle from the Upper Jurassic of the NeuquénBasin, Patagonia, Argentina. Here we describe in detail a new skull, lower jaw, and a vertebra, utilizing both traditionalanatomical description and computed tomography (CT). New diagnostic cranial characters of Neusticemys neuquina are:a round depression on the ventral surface of the basisphenoid, a relatively larger oval foramen nervi trigemini, andreduced and steepened triturating surfaces on both the maxilla and dentary. The new morphological information presentedin this study was included in a phylogenetic analysis, the primary result of which was recovery of Neusticemysneuquina within Thalassochelydia. Characters recognized as synapomorphies of this clade include: (1) anterolateralrecess of the anterior surface of the quadrate positioned lateral to the processus trochlearis oticum, (2) presence of afossa on the supraoccipital-opisthotic-exoccipital contact area, (3) foramina anterius caroticus cerebralis located closetogether but independently perforating the basisphenoid, and (4) the presence of the splenial in the mandible. Twocontrasting dispersal scenarios could explain how this species of Thalassochelydia can be found outside of Europe. Thepresence of Neusticemys neuquina in the Neuquén Basin could be the consequence of an early dispersion event, forwhich we lack intermediate forms, or it could be the result of a later event once the clade was already established in Europe.