Print version ISSN 0001-3765
An. Acad. Bras. Ciênc. vol.74 no.2 Rio de Janeiro June 2002
ALDIRENE C. FRANCO-ROSAS *
Instituto de Geociências, Departamento de Geologia, UFRJ, RJ.
Presented by ALEXANDER W.A. KELLNER
Isolated teeth of small theropods are relatively common in Brazilian Cretaceous deposits, where several well-preserved specimens have been found. Here we describe and present morphological and morphometric parameters that can be used for the taxonomic identification of such material. This study is based on thirty teeth from four sites situated in the São Paulo and Minas Gerais states. This material comes from the Adamantina and Marilia formations of the Bauru Basin and was examined under stereomicroscope and scanning electron microscope.
The following characteristics were considered effective for the characterization of different morphological classes, some of which were already mentioned in the literature: 1 - number of denticles per millimeter (DPM), which is measured in the central region of the posterior margin; 2 - tooth base diameter (BW); 3 - preserved portion of the tooth total height (AT); 4 - shape of the basal transverse section (FABL); 5 - shape of the denticles. Based on the features above three morphologic groups were identified, tentatively referred to the Maniraptoriformes (Dromaeosauridae, Velociraptorinae and Troodontidae) as follows:
Morphotype 1 - long, rounded denticles showing a non-uniform distal portion and different slopes, with slightly pronounced interdenticle spaces. This morphology is similar to the teeth described for Velociraptorinae and Troodontidae.
Morphotype 2 - long, sharp denticles in the distal portion, with deep rifts among them. This morphology is very similar to the one shown by North American specimens, associated with Dromaeosauridae.
Morphotype 3 - short, round denticles, with bow-shaped distal portion and deep interdenticle spaces, not recorded before. They might represent a new group, endemic for Brazil. ( December 20, 2001 ).