The anuran pelvis: Evidence for the phylogenetic placement of the Tiupampan Estesiella boliviensis

GÓMEZ, R.O.; BÁEZ, A.M.

San Luis

Congreso; XXV Jornadas Argentinas de Paleontología de Vertebrados; 2010

Universidad Nacional de San Luis

The neobatrachian frog Estesiella boliviensis (Báez, 1991) from the early Paleocene Santa Lucia Formation exposed at Tiupampa, Bolivia, was originally referred to Leptodactylidae, although this taxon was loosely defined at that time. Recently, many former leptodactylids have clustered with different groups of hyloids, primarily on molecular grounds, calling for a revision of the evolutionary relationships of Estesiella. With this aim, we focused on the pelvic morphology because the ilium has been regarded as a ?key element? in the taxonomic identification of fossil anurans and the pelvic girdle is well represented among the remains ascribed to this taxon. A detailed study of this skeletal part in Estesiella and major lineages of anurans, combining traditional and geometric morphometrics, was undertaken. Observed variation was partitioned into characters and character states; as some of this variation occurs continuously the corresponding characters were consequently coded as such. Phylogenetic analyses including 23 characters of the pelvic girdle and a molecular dataset for 60 taxa taken from the literature were performed in TNT 1.0 under implied weights. Estesiella consistently emerges in a basal position within nobleobatrachian hyloids (i.e. more derived than australobatrachians). Noteworthy, molecular clock estimates dated the diversification of nobleobatrachians as a Paleocene event. Hence, more resolution in the systematic position of Estesiella becomes critical in dating the nobleobatrachian radiation.