Isolated teeth of small theropods from the El Gallo Formation, Baja California, Mexico

Abstract

In this work, 47 isolated small theropod teeth from different microsites of “El Gallo” Formation, Baja California, Mexico are studied. Isolated theropod teeth constitute important evidence to analyse theropod diversity, since they are quite common in the fossil record. For their identification, we conducted morphological comparisons using multivariate and cladistic analyses comparing them with previously described small theropod teeth from Upper Cretaceous North America Formations. This dental material can be assigned mainly to two families: Dromaeosauridae, Troodontidae; and one subfamily: Saurornitholestinae. Also, some of the teeth were assigned to Richardoestesia and two specimens were indeterminate. Dromaeosaurids represent the most abundant group of theropods in “El Gallo” followed by the Richardoestesia dental Morphotype. This diversity pattern is similar to the one reported in the Aguja Formation of Texas for the same period of time. The use of multivariate statistical techniques and cladistic analyses allowed us to evaluate the similarity between specimens, however, taxonomical assignments are difficult due to the lack of knowledge of intraspecific morphological and/or ontogenetic variation that can lead to misinterpretations. Even so, the sample of 47 specimens yields valuable information that allows suggesting the presence of certain taxa and providing knowledge of the diversity of the continental Cretaceous fauna in Mexico.