Cenozoic marine turtle record from southern South America: new insights from the Miocene of Patagonia, Argentina

JULIANA STERLI; EVANGELOS VLACHOS; JOSÉ CUITIÑO; MÓNICA. R. BUONO; MARIANA VIGLINO

Virtual Meeting

Otro; 9th International Meeting on the Secondary Adaptation of Tetrapods to Life in Water Virtual Meeting; 2021

The study of marine turtles is a challenging topic because of the cosmopolitan nature of itsfossil record and current distribution. Thus, it might be difficult to study and comparespecimens, but sometimes even the smallest fragments or isolated occurrences might providesignificant new information for the whole group. The Cenozoic fossil record of marine turtles(Pan-Chelonioidea) in South America is scarce with less than 10 published occurrences. Thesouthernmost published record corresponds to a fragmentary and undetermined specimen ofpan-dermochelyid (MPEF-PV 565) from the lower Miocene Gaiman Formation in Chubutprovince, Patagonia, Argentina. However, recent fieldwork has significantly increased therecord of marine turtles from northeastern Chubut. The fossil record of pan-dermochelyidswas increased with two findings from the Gaiman Formation: one fragmentary consisting oftwo ossicles (MPEF-PV 11360) and an almost complete carapace with associatedpostcranium (MPEF-PV 10918). Furthermore, also from the Gaiman Formation, a lower jawof a pan-cheloniid (MPEF-PV 11382) was found. This group was also recently found in theupper Miocene Puerto Madryn Formation, represented by shell and postcranial remains(MPEF-PV 10929) and a skull (MPEF-PV 2577) coming from Gaiman or Puerto Madrynformations. In summary, we can conclude that: (1) the northeastern Chubut presents the mostdiverse and abundant record of chelonioid turtles in the Atlantic coast of South America; (2)the reported pan-cheloniid specimens expand the stratigraphic and geographic range of thegroup in the Atlantic coast in the Neogene; (3) the almost complete carapace of apan-dermochelyid represents one of the most complete specimens of the group foundup-to-date in the world. Thus, these new findings will provide valuable information on theanatomy, taxonomy, and diversity of the marine turtles that once populated the southwesternAtlantic sea and coasts of southern South America.