Cretaceous Antarctic plesiosaurs: stratigraphy, systematics and paleobiogeography
Jose Patricio O’GORMAN1,2*, R. OTERO3, M REGUERO1,4 & Z GASPARINI1,2
1División Paleontología Vertebrados, Museo de La Plata, Universidad Nacional de La Plata, Paseo del Bosque s/n., B1900FWA La Plata, Argentina;
2CONICET: Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina, Godoy Cruz 2290, C1425FQB, CABA, Argentina;
3Red Paleontológica U-Chile, Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile;
4Instituto Antártico Argentino, 25 de Mayo 1143, B1650HMK, San Martín, Buenos Aires, Argentina.
Received 28 December 2018; accepted 22 May 2019; published online 22 May 2019
The last twenty million years (Maastrichtian-Santonian) of Southern Hemisphere plesiosaur history is especially well recorded in the Weddellian Province (Patagonia; Western Antarctica and New Zealand). The oldest Late Cretaceous plesiosaurs, two specimens referred to Polycotylidae indet., come from the Santonian levels of the Santa Marta Formation, while the oldest elasmosaurids come from the lower Campanian of the same formation. In the lower Maastrichtian of the Snow Hill Island Formation the non-aristonectine elasmosaurid Vegasaurus molyi is recorded together with other non-diagnosable elasmosaurid specimens, but no aristonectines are present. Aristonectines appears in the Antarctic record in the upper Maastrichtian of the López de Bertodano Formation and are represented by Morturneria and cf. Aristonectes. The specimens from the upper Campanian previously referred to Aristonectinae indet. are reffered to Elasmosauridae indet., shortening the temporal record of Aristonectinae in Antarctica. Therefore aristonectines appears in the Antarctic record in the upper Maastrichtian of the López de Bertodano Formation and are represented by Morturneria and cf. Aristonectes. The Antarctic Cretaceous elasmosaurids show a paleobiogeographic connection with South America and New Zealand (Weddellian Province). This connection is indicated by the shared presence of the Aristonectinae Kaiwhekea katiki (New Zealand) and Aristonectes (Argentina and Chile). Recent phylogenetic analysis recovered the aristonectines within the Weddellonectia clade, which includes the aristonectines and the non -aristonectines Vegasaurus molyi (Isla Vega, Antarctica); Kawanectes lafquenianum (Argentina); Morenosaurus stocki and Aphrosaurus furlongi (California). Among the Weddellonectia, the aristonectines show a relatively large body size and an extremely derived features and probably occupied a trophic niche that differed from the trophic niche of other elasmosaurids. By way of contrast Kawanestes lafquenianum is an extremely small body sized elasmosaurid restricted to marginal marine (probably estuarine) environments. Therefore the Weddellonectia show high morphological and probably high ecological diversity.
Elasmosauridae; Aristonectinae; Polycotylidae; Santa Marta Formation; Snow Hill Island Formation; López de Bertodano Formation; Weddellonectia
O’Gorman J P, Otero R, Reguero M, et al. Cretaceous Antarctic plesiosaurs: stratigraphy, systematics and paleobiogeography. Adv Polar Sci, 2019, 30(3): **-**, doi: 10.13679/j.advps.2018.0049