Ontogenetic skull variation in the argentinean extant caimans: Caiman latirostris and Caiman yacare (Crocodylia, Alligatoridae)

MARÍA VICTORIA FERNANDEZ BLANCO; PAULA BONA; ITATI OLIVARES; JULIA BRENDA DESOJO

Barcelona

Congreso; 10th International Congress of Vertebrate Morphology; 2013

The extant species of Caiman comprise C. crocodilus, C. yacare and C. latirostris, widely distributed in South America. The Argentinean species C. yacare andC. latirostris have been the focus of several morphological studies. Even though several quantitative and qualitative analyses on morphological interspecific variation were done, the intraspecific variation has been poorly explored.We studied 53 post-hatching skulls of C. yacareand C. latirostris. An allometric analysis was performed with 12 linear variables. Morphological variation was assessed by a 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 widths variables exhibited higher intercept values in C. latirostris. The Aws presented the highest slope in C. latirostris. The ontogenetic variation of the snout was assesed with a regression between width and length of the snout. C. latirostris displayedisometry and higher values of slope and C. yacare negative allometry. Similar trajectories could be reflecting 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. This is probably a derived condition within caimanines associated with ecological requirements.