DEUFEL, A. *; BRUCE, S. D.; Minot State University; Minot State University: Burrowing with a Kinetic Snout in a Snake (Elapidae: Aspidelaps scutatus)

Few elongate, fossorial vertebrates have been examined for their mechanics of burrowing. Of those that have, all were found to use an akinetic, reinforced skull to push into the soil, powered mostly by contractions of trunk muscles. In contrast, we have found that the shield-nosed cobra (Aspidelaps scutatus, a snake of the family Elapidae) burrows using a kinetic snout that is independently mobile with respect to the rest of the skull. In shield-nosed cobras the head is short, broad, and bears a greatly enlarged rostral scale, which has protruding, vertically-oriented, shovel-shaped lateral edges. Two mechanisms of burrowing are used: 1) anteriorly directed head thrusts during which the body is thrown into a number of loose curves, pushed against the walls of the tunnel to create friction, and the head is extended from a gathered position of the anterior trunk, and 2) side-to-side shovelling using the rostral scale during which the rostral scale and snout are first passively deflected by the material being shovelled aside and the snout then returns to its rest position before continuing to move in the same direction as the head. The premaxilla, to which the rostral scale is attached, lacks any direct muscle attachments. Rostral scale movements are powered by retractions of the palato-pterygoid bar mediated by a ligament that connects the anterior end of the palatine to the transverse process of the premaxilla. In derived snakes, palatomaxillary movements are highly conserved and underlie the mechanisms of prey capture and transport. Aspidelaps scutatus has co-opted these mechanisms for a novel function. Digging with a mobile snout is a fundamentally different mechanism from that used by many other elongate vertebrates.