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

SEGURA, VALENTINA; PREVOSTI, FRANCISCO

Joao Pessoa

Congreso; 8° Congreso Brasileiro de Mastozoologia; 2015

Sociedade Brasileira de Mastozoologia

The skull ontogeny ofspecialized mammals is relevant to understand the connection of form andfunction in a developmental, ecological, and evolutionary context. The Family Canidae is present in the Neotropical region from 2.6million 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 ofadults (more carnivorous or omnivorous diets) must be accompanied by pronouncedmodifications in skull morphology. The aim of our work wasto study the skull ontogeny of Neotropical canids, exploring the acquisitionof 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 ofNeotropical canids. The sample comprised both juveniles and adults of differentage classes, estimated by dental eruption and tooth wear. A GeneralizedProcrustes Analysis and a principal component analysis were performed. For eachspecies we included Procrustes distance (PD) and centroid size (CS) data, whichwere used to ascertain at which age class the adult skull size (CS) and adultshape (PD) were reached. The most common pattern found among Neotropical canidswas 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. Thedistribution of the species in the morphospace was quite homogeneous, withadults placed to negative values showed elongated cranium with narrower,flatter and longer braincase and muzzle, narrower and elongated mandibularcorpus, straight and narrower mandibular ramus, and juveniles placed to positivevalues with the opposite configuration. The exception was <Speothos venaticus>, which wasdifferent in its entire ontogenetic trajectory. They showed massive adultskulls with short and tall braincase, small bullas, short muzzle, welldeveloped zygomatic arches, and curved, short and wide mandibular corpus. TheJuvenile skulls showed no large difference from adult skulls. <S. venaticus> is theonly Neotropical canid with a hyper-carnivorous diet, and the configuration ofits skull (i.e. short rostrum) allows producing higher bite forces, necessaryto catch and process its preys. All the differences found between adult andjuvenile configurations were related to the reinforcement of the skull and theenhancement of predatory skills in adult Neotropical canids. Theevolution of ontogenetic change in the Neotropical canids seems to be moreinfluenced by diet instead of phylogeny, although differences with <S. venaticus> could be related to that itbranched off its sister group (<Chrysocyon brachyurus>) 3 million yearsago, and with the rest of canids from 4.3 million years ago.