First description of scleractinian corals from the Santa Marta and Snow Hill Island(Gamma Member) formations, Upper Cretaceous, James Ross Island, Antarctica

摘要

Antarctic corals are known from the Upper Cretaceous Santa Marta Formation(Santonian–early Campanian)and Gamma Member(late Campanian)of Snow Hill Island Formation(late Campanian–early Maastrichtian)but they have not so far been taxonomically described.We describe three corals taxa based on 29 specimens collected in 2007 and 2016 on James Ross Island(northeast of the Antarctic Peninsula).They represent the first formal record of scleractinian corals from the Santa Marta Formation,identified as Caryophylliidae indet.and Gamma Member of Snow Hill Island Formation,identified as Astreopora sp.and Fungiacyathus deltoidophorus.The family Caryophylliidae and the genus Astreopora were not restricted to the Weddellian Biogeographic Province but the species Fungiacyathus deltoidophorus was endemic to Antarctica during the Cretaceous.The genus Fungiacyathus and the family Caryophylliidae thrive in Antarctica until the present day.Fungiacyathus occurred in shallower environments during the late Campanian than today.No specimens related to Astreopora have yet to be found in Antarctica after the late Campanian.This can be explained by the capacity of Fungiacyathus and Caryophyllidae to endure cold waters,since they are asymbiotic corals.The symbiotic Astreopora sp.,due to its sensitivity to low temperatures,became extinct in this continent as soon as the Antarctic waters began to cool,around the Campanian/Maastrichtian.The presence of Astreopora sp.in Gamma Member of Snow Hill Island Formation may represents the first occurrence of this genus in Antarctica and the oldest record of this genus in the Southern Hemisphere.