Abstract

Mosasaurs were a specialized clade of marine squamates with global distribution during the Upper Cretaceous and their presence is relatively frequent in Maastrichtian levels of Central Chile and Antarctica. However, until now, the group was absent in Cretaceous units from Southern Chile. Herein we report for the first time the presence of this clade in Upper Cretaceous levels of the Dorotea Formation, Magallanes Region. The material comprises a concretionary block with caudal vertebrae recovered from Sierra Dorotea, near Puerto Natales. Despite the fragmentary nature of the specimen, this record confirms the presence of mosasaurs in the Magallanes Basin, adding new taxa to the known local diversity of marine reptiles so far just represented by elasmosaurid plesiosaurs. This new record allows to making connections with the previous occurrences of mosasaurs from the James Ross Basin in Antarctica, adding new data to the marine herpetofauna in the Weddellian Biogeographic Province