Unusuall shell anatomy and osteohistology in a new Upper Cretaceous panchelid turtle from northwestern Patagonia (Argentina)

DE LA FUENTE MARCELO SAUL; MANIEL IGNACIO JORGE; JANNELLO JUAN MARCOS; STERLI JULIANA; GARRIDO ALBERTO CARLOS; GARCÍA RODOLFO; SALGADO LEONARDO; CANUDO JOSE IGNACIO; BOLATTI RAÚL

ACTA PALAEONTOLOGICA POLONICA

INST PALEOBIOLOGII PAN

Lugar: Varsovia; Año: 2017

0567-7920

Rionegrochelys caldieroi gen. et sp. nov. is a Late Cretaceous turtle from northern Patagonia (Argentina).The holotype and the referred specimens of this new species show an unusual shell morphology and microanatomy. The proportion between the carapace and plastron and the peculiar morphology of the shell such as the heart shaped carapace, a very deep nuchal notch, peripheral bones 2 to 11 with strongly gutter, the first vertebral scute twice as wide as long and subrectangular in shape, the posterior margin of vertebral scute 5 is three lobeshaped, and the unexpected osteohistology characterized by a massive structure, with higher compactness (80.6 %) than other chelids, suggests beyond doubt that these specimens may be considered a new taxon. A semiaquatic habitat with tendency to terrestrial environments is inferred for Rionegrochelys caldieroi similar to that of the extant pelomedusid Pelomedusa subrufa among the extant pleurodires. Rionegrochelys caldieroi has recovered as a pan-chelid. This new species seems to be closely related to Bonapartemys bajobarrealis and the clade formed by Lomalatachelys neuquina plus Mendozachelys wichmanni.