Meeting Abstract

43.4  Wednesday, Jan. 5  The influence of fossoriality on cranial architecture in caecilian amphibians (Gymnophiona) MADDIN, H.C.*; WAKE, M.H.; KRISTENSEN, E.; Univ. of Calgary; Univ. of California, Berkeley; Univ. of Calgary hcmaddin@ucalgary.ca

Fossoriality, wherein the head is employed as the primary locomotor organ (i.e., head-first burrowing), has evolved multiple times independently within Tetrapoda. Among these, caecilians have been shown to exert some of the greatest forces against the substrate during burrowing, and this has been attributed to their unique mode of hydrostatic locomotion. In order to gain a clearer understanding of the features associated with their forceful mode of fossoriality, the skulls of caecilians were examined from both morphological and mechanical perspectives. Examination of cranial architecture reveals elements of the dermal skull form lap joints with adjacent elements in the anteroposterior direction, whereas overlap between elements in the mediolateral direction is minimal or absent. Dense networks of collagen fibres span the joint surfaces. In addition, nostrils are rimmed with cartilage throughout life, and joints between certain elements (e. g., maxilla and braincase) are filled with cartilaginous plugs, also predominantly oriented in the anteroposterior direction. Results of finite element analysis support the hypothesis that cranial joints together with strategically placed cartilages form a complex dampening system, capable of reducing the transmission of compressive forces to the braincase and throughout the dermal skull produced during head-first burrowing. These features contrast somewhat with those known for other fossorial tetrapods, and may thus represent important adaptations associated with the style of burrowing and the greater forces being applied to the skulls of caecilians.