Ontogenetic cranial variation in C. latirostris (Crocodylia: Alligatoridae): a quantitative approach

MARÍA VICTORIA FERNANDEZ BLANCO; PAULA BONA; JULIA BRENDA DESOJO

Capital Federal

Congreso; XI Congreso Argentino de Herpetología; 2010

Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"

Caiman latirostris Daudin is the widest snouted Caiman extant species of Caimaninae alligatorids, characterized taxonomically only by external morphological features. Although its skull differs osteologically from that of other caimans, intraspeciphic variation was never analyzed. In this contribution we present a quantitative analysis that was carried out on the skull of specimens of different sizes of C. latirostris and C. yacare. The relationship between several cranial measurements (e.g. total cranial length, snout length) and the overall cranial size was analyzed through the allometric equation in both species. As a result we obtained a high positive correlation between skull traits and the overall skull size. In both species the snout length increases with positive allometry through ontogeny. Contrary to C. yacare, in C. latirostris the interorbital space increases isometrically while increasing the skull length. In C. yacare the anterior snout width increases isometrically with the skull length (probably establishing the final snout shape in young specimens), but in C latirostris this growth shows positive allometry, determining a change of the snout shape during ontogeny. These hypotheses would be tested in future morphometric analysis in a bigger sample of specimens of these species in order to discriminate potential diagnostic characters of C. latirostris.