Neoselachians and Chimaeriformes (Chondrichthyes) from the latest Cretaceous-Paleogene of Sierra Baguales, southernmost Chile. Chronostratigraphic, paleobiogeographic and paleoenvironmental implications

摘要

This paper discusses a well-represented fossil record of cartilaginous fishes (Chondrichthyes) from southern South America. The recovered samples allow the recognition of three assemblages with chronostratigraphic and paleogeographic value: ⅰ) typical Maastrichtian sharks and rays with affinities to eastern Pacific fauna, including the taxa Ischyrhiza chilensis, Serratolamna serrata, Centrophoroides sp. associated to Carcharias sp., and Dasyatidae indet.; ⅱ) a scarce reworked assemblage of Paleocene-Early Eocene age including the taxa Otodus obliquus and Megascyliorhinus cooperi; ⅲ) a rich assemblage with reworked taxa of Early to Middle Eocene age, together with autochthonous deposited Middle to Late Eocene taxa with close affinities to paleoichthyofaunas recovered from the North Atlantic, represented by Carcharias 'hopei', Odontaspis winkleri, Carcharoides catticus, Macrorhizodus praecursor, Carcharocles auriculatus, Striatolamia sp., Striatolamia macrota, Hexanchus agassizi, Notorhynchus sp., Myliobatis sp., Abdounia sp., Pristiophorus sp., Squatina sp., cf. Rhizoprionodon sp., Ischyodus sp., and one new species, Jaekelotodus bagualensis sp. nov. The studied samples include for the first time taxa with well established chronostratigraphic resolutions as well as taphonomic information that help clarifying the age of the fossil-bearing units. In addition, they provide relevant information about the evolution of the Magallanes (=Austral) Basin from the Upper Cretaceous to the Paleogene, suggesting a probable connection with the Quinquina Basin of south-central Chile during the latest Cretaceous. Finally, the studied assemblages indicate a latitudinal pattern of distribution that provides valuable data on the environmental evolution and temperature of southern South America during the Paleogene.