Skull ontogeny in Neotropical canids (Carnivora, Canidae): A three-dimensional geometric morphometric approach

SEGURA, V.; PREVOSTI, F. J.

Congreso; 8º Congresso Brasileiro de Mastozoologia; 2015

The skull ontogeny of specialized mammals is relevant to understand the connection of form and function in a developmental, ecological, and evolutionary context. The Family Canidae is present in the Neotropical region from 2.6 million years ago, and includes 11 species. Canids are versatile in their diet, varying from hyper-carnivorous to some that contain less than 5% protein. The transition from milk suckling to the demanding feeding habits of adults (more carnivorous or omnivorous diets) must be accompanied by pronounced modifications in skull morphology. The aim of our work was to study the skull ontogeny of Neotropical canids, exploring the acquisition of definitive shape and size in relation to key life-history events. For this purpose, we used geometric morphometrics technique in three-dimensions. We digitized 38 cranial and 18 mandibular landmarks of 1045 skulls of Neotropical canids. The sample comprised both juveniles and adults of different age classes, estimated by dental eruption and tooth wear. A Generalized Procrustes Analysis and a principal component analysis were performed. For each species we included Procrustes distance (PD) and centroid size (CS) data, which were used to ascertain at which age class the adult skull size (CS) and adult shape (PD) were reached. The most common pattern found among Neotropical canids was to reach the final skull shape before skull size. The PC1 summarized 28.90% of the explained variation to the cranium, and 14.98% to the mandible. The distribution of the species in the morphospace was quite homogeneous, with adults placed to negative values showed elongated cranium with narrower, flatter and longer braincase and muzzle, narrower and elongated mandibular corpus, straight and narrower mandibular ramus, and juveniles placed to positive values with the opposite configuration. The exception was , which was different in its entire ontogenetic trajectory. They showed massive adult skulls with short and tall braincase, small bullas, short muzzle, well developed zygomatic arches, and curved, short and wide mandibular corpus. The Juvenile skulls showed no large difference from adult skulls. is the only Neotropical canid with a hyper-carnivorous diet, and the configuration of its skull (i.e. short rostrum) allows producing higher bite forces, necessary to catch and process its preys. All the differences found between adult and juvenile configurations were related to the reinforcement of the skull and the enhancement of predatory skills in adult Neotropical canids. The evolution of ontogenetic change in the Neotropical canids seems to be more influenced by diet instead of phylogeny, although differences with could be related to that it branched off its sister group () 3 million years ago, and with the rest of canids from 4.3 million years ago.