Abstract

The present work describes fossil teeth collected from two Campanian localities: Cerro Guido and Río de las Chinas Valley, Última Esperanza Province, Magallanes and Chilean Antartic Region. The Cerro Guido level has been described as medium grained sandstones (feldspathic litharenite) with a level of elongated calcareous concretions, which conforms part of Tres Pasos Formation (Campanian). The studied teeth were found in association with fragmented ammonites of the species Hoplitoplacenticeras plasticum. In Río de Las Chinas Valley, a coarsening upward sandstone sequence that is part of Dorotea Formation (Campanian- Maastrichtian) was found, which contains an association of bivalves, gastropods, ammonites and, at upper levels, fragmentary bones of indeterminate marine reptiles. The specimens, referred to genus Carcharias (Lamniformes: Odontaspididae), have a slightly inclined tooth crown with a smooth cutting edge, labially smooth with wide base and one or two pairs of well-developed triangular cuspids. Lingually, the base of the crown has vertical ridges and bilobed root with slightly straight lobes. The association of ammonites belonging to the species Hoplitoplacenticeras plasticum supports a Campanian age for both hosting-levels. Although the material from both units is scarce and the chronostratigraphic range of Carcharias is wide, the described specimens are morphologically distinguishable from other species of this genus previously known in Upper Cretaceous sedimentary sequences of Chile. This is the oldest finding of sharks in the Magallanes Basin.