Eternauta patagonica gen. et sp. nov.: a new ophthalmosaurid ichthyosaur from the Upper Jurassic of Patagonia and its palaeoecological implications

CAMPOS, LISANDRO; FERNÁNDEZ, MARTA S.; HERRERA, YANINA; TALEVI, MARIANELLA

Historical Biology

Taylor&Francis

Año: 2025 p. 1 - 24

0891-2963

Ophthalmosaurids were a globally distributed clade of ichthyosaurs that thrived from the MiddleJurassic to the early Late Cretaceous. Although their fossil record spans a wide palaeogeographicrange, much of what is known about their anatomy and diversity derives from Late Jurassiclocalities in the Northern Hemisphere. In contrast, Late Jurassic forms from the SouthernHemisphere remain comparatively less known. Here we describe Eternauta patagonica gen. etsp. nov. a new ophthalmosaurid from the Tithonian deposits of the Vaca Muerta Formation. Theholotype, previously referred to Caypullisaurus bonapartei Fernández, 1997, comprises a skull,teeth, a forelimb, and rib fragments. Phylogenetic analyses consistently recover Eternauta asa member of Platypterygiinae. Diagnostic features include a unique morphology of the pterygoid,an expanded postorbital contribution to the ventral margin of the orbit, and a retroarticularprocess that is strongly angled posterodorsally. These traits, together with a low jaw-openingmechanical advantage and relatively large sclerotic aperture, suggest a feeding strategy forcapturing small, agile prey. The anatomical and functional features of Eternauta expand theknown morphological and ecological disparity of Late Jurassic ophthalmosaurids, reinforcing thesignificance of the Vaca Muerta Formation as a key unit for understanding ichthyosaur evolutionacross the Jurassic – Cretaceous transition.