Vegasaurus molyi, gen. et sp. nov. (Plesiosauria, Elasmosauridae), from the Cape Lamb Member (lower Maastrichtian) of the Snow Hill Island Formation, Vega Island, Antarctica, and remarks on Wedellian Elasmosauridae

O'GORMAN, J.P.; SALGADO, L.; OLIVERO, E.B.; MARENSSI, S.A.

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2015

0272-4634

A new elasmosaur, Vegasaurus molyi gen. et sp. nov., from Vega Island, James Ross Archipelago, Antarctica, is described. The holotype and only specimen of this species (MLP 93-I-5-1) was collected from the upper Campanian-lower Maastrichtian Snow Hill Island Formation. Vegasaurus molyi gen. et sp. nov. is the only Antarctic elasmosaur and one of the few Upper Cretaceous elasmosaurs from the South Hemisfere whose postcranial anatomy is well-known. Vegasaurus molyi gen. et sp. nov. is distinguished from other elasmosaurs by the following combination of characters: cervical region with fifty-four vertebrae with elongated centra, dumbbell-shape articular faces and lateral ridge present in the anterior part of the neck, but with theseis two features being absents in the posteriormost cervical vertebrae of the series; scapula with ventral ramus bearing a strong ridge in the anteromedial corner of its dorsal surface; dorsolateral process of scapula rectangular-shaped, forming and angle of 140º with the ventral ramus; coracoid with mid-ventral process; absence of pectoral and pelvic bars; ilium shaft divided in two parts, forming an angle of 140º; ilium with expanded distal end; humerus with anterior knee and strong posterior projection with accesory posterior articular facet. Preliminary phylogenetic analysis places V. molyi gen. et sp. nov. within a clade that comprises all Late Cretaceous Wedellian Aristonectinae elasmosaurs, such as Aristonectes and Kaiwhekea. This indicates a close relationship between the Aristonectinae and the non- Aristonectinae Late Cretaceous Weddellian elasmosaurs, and suggestsand a probable Weddellian origin for the Aristonectinae. Vegasaurus molyi gen. et sp. nov. does not belong to the ?elongate group? sensu O´Keefe and Hiller (2006), supporting the hypothesis that the ?elongate group? is geographically restricted to the Western Interior Sea.