Bite-force performance of the last rhynchocephalian (Lepidosauria: Sphenodon)

Abstract

We present the first empirical measurements of bite‐force performance from adult Sphenodon (Rhynchocephalia), the only extant non‐squamate lepidosaur. Using raw bite‐force data, we calculated maximum bite forces at the anterior and posterior extremes of the lower tooth row: 81.8 N and 163.5 N (female) and 119.1 N and 238.3 N (male). Combining our results with published data from juvenile animals, we calculated scaling coefficients of bite force on linear morphometrics of body and head size as c. 2.7 (anterior) and c. 3.5+ (posterior). These exceed isometric scaling predictions (2.0), yet are similar to those for other non‐avian reptiles. This supports previous views that Sphenodon cannot bite as hard as agamid lizards. We discuss the role of bite force in the behavioural ecology of Sphenodon, propose that the lower temporal bar, unique among extant lepidosaurs, does not necessarily constrain bite force, and evaluate possible effects of other morphological characteristics on bite‐force performance.