Skull ontogeny of extant caimans: a three-dimensional geometric morphometric approach

BLANCO, MARÍA V. FERNANDEZ; CASSINI, GUILLERMO H.; BONA, PAULA

ZOOLOGY

ELSEVIER GMBH

Año: 2018

0944-2006

Ontogenetic variation of cranial characters used in crocodylian phylogenetic systematics has never been studied.Furthermore, the relationship between diet and skull morphological transformation during ontogeny hasnot been properly explored yet. We quantify the inter- and intraspecific skull morphological variation in extantcaiman species focusing on those areas relevant to systematics and, also investigate the relation between diet andmorphological changes during ontogeny. We applied a three-dimensional approach of geometric morphometricson post-hatching ontogenetic cranial series of Caiman latirostris and C. yacare. In order to incorporate incompletematerial, we additionally tested four different methods of missing landmark estimation and apply the thin-platespline interpolation. We detected morphological changes between species and during ontogeny (snout and pterygoidflanges increase their proportions and, orbits, temporal fenestrae, skull roof and foramen magnum decreasetheir relative size) that constitutes part of a general morphological change in the cranial ontogeny of crocodylians.Moreover, the negative allometry of the fenestrae and neurocranium and the positive allometry of thesplanchnocranium in both caiman species are the plesiomorphic condition, at least, for tetrapods. Shape changesduring growth were found to be related to ontogenetic changes in the diet. Dissimilarities between species seemto be related to different mechanical requirements and different use of the habitat. We found inter- and intraspecificvariation in some morphological characters with systematic implications (the contact of nasals with naris,the contact of prefrontals in the midline, and the bones that border the suborbital fenestra and the proportion inwhich one of them participates) that are not currently considered in phylogenetic analyses.