Intraspecific variation in the skullmorphology of the black caiman Melanosuchus niger (Alligatoridae, Caimaninae)

FOTH, C.; BONA, P.; DESOJO J.B.

ACTA ZOOLOGICA

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 p. 1 - 13

0001-7272

Melanosuchus niger is a caimanine alligatorid widely distributed in the northernregion of South America. This species has been the focus of several ecological,genetic and morphological studies. However, morphological studies have generallybeen limited to examination of interspecific variation among extant speciesof South American crocodylians. Here, we present the first study of intraspecificvariation in the skull of M. niger using a two-dimensional geometric morphometricapproach. The crania of 52 sexed individuals varying in size were analysed toquantify shape variation and to assign observed shape changes to different typesof intraspecific variation, that is, ontogenetic variation and sexual dimorphism.Most of the variation in this species is ontogenetic variation in snout length, skulldepth, orbit size and the width of the postorbital region. These changes are correlatedwith bite force performance and probably dietary changes. However, acomparison with previous functional studies reveals that functional adaptationsduring ontogeny seem to be primarily restricted to the postrostral region,whereas rostral shape changes are more related to dietary shifts. Furthermore,the skulls of M. niger exhibit a sexual dimorphism, which is primarily sizerelated.The presence of non-size-related sexual dimorphism has to be tested infuture examinations.