New Finds Increase Late Cretaceous Antarctic Plesiosaur Diversity

Additions to the diversity of elasmosaurid plesiosaurs from the Upper Cretaceous of Antarctica

Authors:

1. Rodrigo A. Otero (a)
2. Sergio Soto-Acuña (a, b)
3. Alexander O. Vargas 9a)
4. David Rubilar-Rogers (b)
5. Roberto E. Yury-Yañez (c)
6. Carolina S. Gutstein (d)

Affiliations:

a. Red Paleontológica U-Chile, Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Av. Las Palmeras 3425, Santiago, Chile

b. Área Paleontología, Museo Nacional de Historia Natural, Casilla 787, Santiago, Chile

c. Laboratorio de Zoología de Vertebrados, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Av. Las Palmeras 3425, Santiago, Chile

d. Laboratorio de Ecofisiología, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile

Abstract:

Three specimens of elasmosaurid plesiosaurs (Sauropterygia, Plesiosauroidea) from Upper Cretaceous beds of Antarctica are described here. These include postcranial remains of a single adult individual recovered from late Maastrichtian beds of Marambio (= Seymour) Island, possessing distinctive cervical vertebrae with the transverse section of the centra having a triangular outline, a vertical groove on the rostral and caudal edge of the neural spines, and a deep articulation over the neural arch for the following postzygapohysis, while the scapula shows an unusually large and anteriorly recurved dorsal process. This combination of features is not known to occur in any adult, postcranial elasmosaurid genus recovered to date in the Upper Cretaceous of the Weddellian Biogeographic Province and could represent a new form. Additional specimens from James Ross Island comprise the first record of an Aristonectinae (Plesiosauria, Elasmosauridae) in late Campanian beds, being the oldest known record of this sub-family. Finally, a third specimen from the same age and locality reveals the presence of very-long necked elasmosaurids with affinities to typical representatives from the Upper Cretaceous of the Northern Hemisphere. These findings add to the known diversity of Upper Cretaceous elasmosaurids in high latitudes of the Southern Hemisphere.