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

O´GORMAN, J; SALGADO, L; OLIVERO, E; MARENSSI, S.

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 early Maastrichtian Cape Lamb Member of the Snow Hill Island Formation (late Campanian-early Maastrichtian). Vegasaurus molyi gen. et sp. nov. is the only Antarctic elasmosaur and one of the few Upper Cretaceous elasmosaurs from the South Hemisphere 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 54 vertebrae with elongated centra, dumbbell-shaped articular faces and lateral ridge present in the anterior part of the neck but absent in the posteriormost cervical vertebrae of the series; scapula with ventral ramus bearing a strong ridge in the anteromedial corner of its dorsal surface; rectangular dorsolateral process of the scapula that forms an 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 accessory posterior articular facet. Preliminary phylogenetic analysis places V. molyi gen. et sp. nov. within a clade that comprises all the Late Cretaceous Wedellian Aristonectinae elasmosaurs, (Aristonectes and Kaiwhekea). This indicates a close relationship between Aristonectinae and non-Aristonectinae Late Cretaceous Weddellian elasmosaurs, and suggests a Weddellian origin for the Aristonectinae.