Calvarial osteoderms and their potential role in Lizard feeding biomechanics

Abstract

Osteoderms (ODs) are calcified hard tissues that develop directly within the dermis of many lizards. They can be found all over the body, or only on some parts of the body (like the head, where intimate connections with the bones of the skull are common). OD’s main role has been commonly considered to be mainly protective, however there are some evidences that they can also have other functions. We investigated the potential role of calvarial ODs in the biomechanics of feeding. Two lizard species were selected: one that has ODs all over its head (Tiliqua scincoides), and one that has ODs only over its temporal region (Timon lepidus). Several experiments were performed to quantify the level of principal strains on one of the temporal ODs while measuring bite force. At the same time, finite element models of both lizards were developed based on micro-CT images. After being validated against the experimental measurements, finite element models were used to further investigate several hypothetical scenarios regarding the function of the ODs, such as having no ODs. Our results show that ODs can have a significant role in reducing the level of strain across the skull during feeding. Perhaps the possession of cranial ODs can enhance the biting performance of some lizards.