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 Cre...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 referred 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 extremely derived features and probably occupied a trophic niche that differed from the trophic niche of other elasmosaurids.By way of contrast Kawanectes 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.展开更多
基金funded mainly by the Dirección Nacional del Antártico and the Instituto Antártico Argentino, project: PICTO 2010-0093Partial funding was provided by the Consejo Nacional de Investigaciones Científicas y Tecnológicas, Agencia Nacional de Promoción Científica y Tecnológica, and Universidad Nacional de La Plata through PICT 2012-0748 and PICT 2015-0678RAO was supported by Proyecto Anillo Conicyt-Chile, ACT 172099 (Conicyt-Chile)
文摘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 referred 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 extremely derived features and probably occupied a trophic niche that differed from the trophic niche of other elasmosaurids.By way of contrast Kawanectes 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.
