THE TAXONOMIC STATUS OF NOTOCAIMAN STROMERI (CROCODYLIA, ALLIGATOROIDEA) AND THE EARLY DIVERSITY OF SOUTH AMERICAN CAIMANINES

BONA, PAULA; BARRIOS, FRANCISCO; EZCURRA, MARTÍN; FERNANDEZ BLANCO, VICTORIA

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2022

0002-7014

The early diversification of caimanines is 32 one of the least understood aspects33 of the evolutionary history of Crocodylia. The Palaeogene Argentinian caimanine34 record is extremely relevant because it provides key information on the early history of35 the clade. Most of the Palaeocene South American species are only or mainly known36 from partial lower jaws. Among the oldest Argentinian caimanines, Notocaiman37 stromeri (middle Palaeocene, Las Violetas Formation, Chubut Province) and Eocaiman38 palaeocenicus (lower Palaeocene, Salamanca Formation, Chubut Province) are39 represented by a partial left dentary and a fairly complete lower jaw, respectively.40 Notocaiman stromeri, described in 1937, has been phylogenetically interpreted from an41 alligatorid closely related to Eocaiman to an indeterminate eusuchian, but a modern42 anatomical revision of this species is lacking. Here, we redescribe in detail the only43 known specimen of Notocaiman stromeri (PVL 752) with the aim of revising its44 taxonomy and phylogenetic relationships. We concluded that Notocaiman and45 Notocaiman stromeri are nomina dubia and we refer PVL 752 to Eocaiman cf. E.46 palaeocenicus. Our phylogenetic analysis found Eocaiman palaeocenicus as the sister47 taxon to the Eocaiman cavernensis + Eocaiman itaboraiensis clade. Thus, here we48 reduce the alpha taxonomic diversity of alligatorids in the Palaeogene of South49 America, but reinforce a geographically broad diversification of the genus Eocaiman,50 from the Palaeocene to the Eocene/Miocene in this continent.