A quantitative approach to the cranial ontogeny of Lycalopex culpaeus (Carnivora: Canidae)

SEGURA, VALENTINA; PREVOSTI, FRANCISCO

Punta del Este

Congreso; 9th International Congress of Vertebrate Morphology; 2010

International Society of Vertebrate Morphology

The cranial ontogeny of specialized mammals is relevant to understand the connection of form and function in a developmental, ecological, and evolutionary context. Lycalopex culpaeus is the largest fox in the genus and is considered more carnivorous and a consumer of large mammalian prey than other South American foxes. The transition from milk suckling to the demanding feeding habits of adults must be accompanied by pronounced modifications in morphology and behavior. We studied the postnatal ontogeny of the skull using a quantitative approach in an ontogenetic series of 101 skulls. They ranged from two months to 11 years old. We use linear measurements and geometric morphometrics. With both methods, we detect a close interaction between neurocranium and splachnocranium, resulting in a modified adult skull, functionally adapted to a more carnivore feeding habits. The trends observed include patterns as the negative allometry of the braincase and the positive allometry of the zygomatic breadth, whose combination determine the space for the temporal musculature. The height of the mandibular ascendant ramus, implied in the insertion of the masseteric muscle, is related with the mechanical resistance. Some features, like strong development of crests (sagittal and lambdoidal), and growth and strengthening of processes (postorbital and postglenoid), are detected only with geometric morphometrics.  Both methods indicate that the major ontogenetic changes are directly linked to cranial structures that support a developing masticatory apparatus and its associated jaw and neck musculature, essential for the action of canines and carnassials during the killing bite and slicing flesh.