ONTOGENETIC SKULL VARIATION IN THE ARGENTINEAN EXTANT CAIMANS CAIMAN LATIROSTRIS AND CAIMAN YACARE (CROCODYLIA, ALLIGATORIDAE)

FERNARNDEZ BLANCO,V; BONA PAULA; OLIVARES, I.; DESOJO, J. B.

Congreso; 10th International Congress of vertebrate morphology; 2013

The extant species of Caiman, C. crocodilus, C. yacare and C. latirostris, are widely distributed in South America. The Argentinean species C. yacare and C. latirostris have been the focus of several morphological studies. Even though several quantitative and qualitative analyses of interspecific morphological variation have been done, intraspecific variation has been poorly explored. We studied 53 post hatching skulls of C. yacare and C. latirostris. An allometric analysis was performed with 12 linear variables. Morphological variation was assessed using principal component analysis (PCA). To test cranial allometry, a simple regression was performed using the scores of the first principal component (PC1) as a size proxy. Comparisons of the slopes were made for both species. All the variables showed high correlation coefficients and negative allometry. Comparative analysis showed common slopes and different intercept for most variables except for the anterior width of the snout (Aws). Trajectories of length variables showed higher intercept values in C. yacare, although trajectories of snout width variables exhibited higher intercept values in C. latirostris. The Aws presented the highest slope in C. latirostris. Ontogenetic variation of the snout was assessed with a regression between width and length of the snout. C. latirostris displayed isometry and higher values of slope than C. yacare, which showed negative allometry. Similar trajectories mayreflect a common ontogenetic pattern of morphological skull change established early in ontogeny for all variables except Aws. The modeling of the snout during ontogeny in C. yacare results in adult forms with generalized snout shapes, which is probably a derived