Bite Force Estimation and the Fiber Architecture of Felid Masticatory Muscles

Abstract

Increasingly, analyses of craniodental dietary adaptations take into account mechanical properties of foods. However, masticatory muscle fiber architecture has been described for relatively few lineages, even though an understanding of the scaling of this anatomy can yield important information about adaptations for stretch and strength in the masticatory system. Data on the mandibular adductors of 28 specimens from nine species of felids representing nearly the entire body size range of the family allow us to evaluate the influence of body size and diet on the masticatory apparatus within this lineage. Masticatory muscle masses scale isometrically, tending toward positive allometry, with body mass and jaw length. This allometry becomes significant when the independent variable is a geometric mean of cranial variables. For all three body size proxies, the physiological cross-sectional area and predicted bite forces scale with significant positive allometry. Average fiber lengths (FL) tend toward negative allometry though with wide confidence intervals resulting from substantial scatter. We believe that these FL residuals are affected by dietary signals within the sample; though the mechanical properties of felid diets are relatively similar across species, the most durophagous species in our sample (the jaguar) appears to have relatively higher force production capabilities. The more notable dietary trend in our sample is the relationship between FL and relative prey size: felid species that predominantly consume relatively small prey have short masticatory muscle fibers, and species that regularly consume relatively large prey have relatively long fibers. This suggests an adaptive signal related to gape. Anat Rec, 295:1336Rec, 295: -1351

Comparative Biomechanical Modeling of Metatherian and Placental Saber-Tooths: A Different Kind of Bite for an Extreme Pouched Predator

“…However, the musculoskeletal configuration of saber-tooths may have allowed them to operate within a more favorable portion of the length–tension curve at larger gapes, as has been demonstrated in some other mammalian taxa [46]. Among living felids there is evidence for increased fiber length in the jaw adductors of species that have wider gapes and that take relatively large prey [47]. This may suggest some mitigation of the tendency to lose muscle force at wide gapes in these species.…”

Go big or go fish: morphological specializations in carnivorous bats

“…In addition to absolute differences in body and skull size, we found positive allometry in skull shape with respect to skull size across bats that consume animal prey. This adds to a body of work stressing the role of allometry in underlying morphological diversity in the mammalian feeding apparatus [17,[60][61][62][63][64][65]. In carnivorous bats, larger sizes are associated with cranial and mandibular traits that increase bite force, gape and jaw closing speed: a taller sagittal crest provides larger attachment area for the temporalis muscle; a longer rostrum produces a wider gape that can accommodate larger prey, and enables faster jaw closure in prey capture [66].…”

“…Carnivorans also exhibit allometric patterns of variation in cranium shape and jaw adductor traits (e.g. larger felids exhibit longer rostra and larger jaw adductor physiological cross-sectional areas [17][18][19]). …”

Complete description of the skull and mandible of the giant mustelidEomellivora piveteauiOzansoy, 1965 (Mammalia, Carnivora, Mustelidae), from Batallones (MN10), late Miocene (Madrid, Spain)

“…Anatomical descriptions are based primarily on Scapino (1968), Turnbull (1970), Barone (1999Barone ( , 2000, Waibl et al (2005), de Lahunta (2010, 2013), and HartstoneRose et al (2012). The terminology conforms to the standard of the Nomina Anatomica Veterinaria (NAV; Waibl et al, 2005), with the exception of the masseter and temporalis muscle complexes for which we follow Hartstone-Rose et al (2012). We provide a description of the main craniodental features of Eomellivora from Batallones, with emphasis on the traits that may indicate its systematic affinities.…”