Chiniquodontid cynodonts: systematic and morphometric considerations

FERNANDO ABDALA; NORBERTO P. GIANNINI

PALAEONTOLOGY

Año: 2002 vol. 45 p. 1151 - 1160

0031-0239

Systematic and morphometric reappraisal of most specimens previously assigned to the cynodont clade Chiniquodontidae reveal that the groups is diagnosed by two synapomorphies: (1) the distinctive angulation betwen the posterior portion of the maxillary and the anterior portion of the zygomatic arch and (2) very extended pterygoid flanges, ending in a thin projection; and a combination of features including: posterior postcanines sectorial with principal cusps backwardly recurved, and a long osseous palate. The species Chiniquodon theotonicus (including Belesodon magnificus, Probelesodon kitchingui, P. lewisi and P. minor) and C. sanjuanensis (comb. nov.) ere the only recognised members of the family on the basis of qualitative characters. The South American species Cromptodon mamiferoides, Probainognathus jenseni and Thrinaxodon brasiliensis are thus excluded from the group, as are the African taxa Aleodon brachyrhamphus and Cistecynodon parvus. Allometric analysis of chiniquodontids sensu stricto reveals that: (1) all specimens can be confidently arranged in a single growth series, irrespective of their original species assignments; and (2) most of the measurements change isometrically with respect to skull length. Adults are virtually scaled-up juveniles, showing a deepened zygoma, a longer osseous palate, and a wider anterior muzzle in the canine region. Thus, allometric data reinforce the proposed synonymy of all forms, with the specific status of C. sanjuanensis supported by qualitative diagnostic traits.