Bite force data suggests relationship between acrodont tooth implantation and strong bite force

Abstract

Extant and extinct reptiles exhibit numerous combinations of tooth implantation and attachment. Tooth implantation ranges from those possessing roots and lying within a socket (thecodonty), to teeth lying against the lingual wall of the jawbone (pleurodonty), to teeth without roots or sockets that are attached to the apex of the marginal jawbones (acrodonty). Attachment may be ligamentous (gomphosis) or via fusion (ankylosis). Generally speaking, adaptative reasonings are proposed as an underlying driver for evolutionary changes in some forms of tooth implantation and attachment. However, a substantiated adaptive hypothesis is lacking for the state of acrodont ankylosis that is seen in several lineages of Lepidosauria, a clade that is plesiomorphically pleurodont. The convergent evolution of acrodont ankylosis in several clades of lepidosaurs suggests a selective pressure shaped the evolution of the trait. We hypothesize that acrodont ankylosis as seen in Acrodonta and Sphenodon punctatus, is an adaptation either resulting from or allowing for a stronger bite force. We analyzed bite force data gathered from the literature to show that those taxa possessing acrodont dentition possess a stronger bite force on average than those taxa with pleurodont dentition. Dietary specialists with pleurodont dentition may also possess relatively high bite forces, though body size may also play a role in their ability to bite hard. Furthermore, our results have implications for the evolution of acrodont ankylosis and potential behaviors related to strong bite force that influenced the evolution of acrodonty within Acrodonta and Rhynchocephalia.

Inter‐relationships among body mass, body dimensions, jaw musculature and bite force in reptiles

“…Positive relationships among measures of body size and bite force have been shown several times previously for within species (e.g. Herrel et al., 2006) and among species (Erickson et al., 2012; Isip et al., 2022; Jenkins & Shaw, 2020). Although explored for birds (Deeming et al., 2022), this study is the first to demonstrate the relationships for body size with total jaw muscle mass, which ultimately generates bite force, are unaffected by order of reptile.…”

“…There is a positive relationship between snout–vent length and bite force in Lepidosauria, which also relates to diet (e.g. Herrel et al., 2014; Jenkins & Shaw, 2020), but see Isip et al. (2022).…”

“…Data for bite force, mainly derived from in vivo studies, are well reported for a wide range of lizards and crocodilians, although less so for testudines and snakes. Inter‐specific comparisons among body dimensions and bite force are limited to a few reports for crocodilians (Erickson et al., 2012), testudines (Herrel et al., 2002) and lizards (Isip et al., 2022; Jenkins & Shaw, 2020). The only study into the interspecific relationship between bite force and the mass of the jaw musculature is for bird species (Deeming et al., 2022).…”

Getting out of a mammalian egg: the egg tooth and caruncle of the echidna

“…In the absence of invagination in the echidna, the dentine made direct contact with the bone for attachment. A fused tooth is sturdier than a tooth attached via soft tissue (Jenkins & Shaw, 2020). An ankylosed connection can also likely be established faster than a thecodont attachment.…”

Clinical and post mortem examination of white worm lizards (Amphisbaena alba) in the State of Paraíba, Northeastern Brazil: morphological, pathological and radiographic findings of a secretive species

“…Amphisbaenians usually feed on invertebrates and even small mammals, and possess strong, recurved teeth and robust jaws. Most amphisbaenians have subpleurodont dentition and replace their teeth throughout life (Jenkins & Shaw 2020).…”