O’REILLY, J.C.*; KLEY, N.J.; RICHMOND, A.M.; BRAINERD, E.L.: Prey Capture Kinematics in Chelus fimbriatus (Testudines: Pleurodira)

Many aquatic turtles can successfully capture elusive aquatic prey but few, if any, approach the abilities of the South American matamata (Chelus fimbriatus). The goal of this project is to use high-speed videography, fluoroscopy and anatomical dissection to gain a better understanding of the exceptional suction feeding abilities of Chelus. Unlike most turtles, the skull of Chelus is dorsoventrally flattened and the distal half of the mandible is reduced to a thin rod of bone. Unlike any other turtle, Chelus possess no lateral gape when the mouth is open; a large flap of skin unfolds at the angle of the gape and restricts the circular mouth opening to a single plane. The hyoid skeleton is large relative to similar sized individuals of other species and very robust, functioning as a four-bar linkage system to expand the pharynx both ventrally and laterally in response to posteriorly directed forces generated by the M. rectus cervicus. In addition to its many morphological peculiarities, the strike of Chelus is much faster than that of any other turtle for which data are currently available (peak gape in 10-15 ms for individuals with 13 cm carapace length). The combination of this unique suite of characters adds up to exceptional suction feeding abilities at the apparent expense of biting performance. The combination of a such an extremely flattened skull with an attenuated mandible, results in Chelus being effectively incapable of biting. This research is supported by a UMass/OEB Darwin Postdoctoral Fellowship to JCO and NSF grant IBN-9875245 to ELB.