Many-to-one function of cat-like mandibles highlights a continuum of sabre-tooth adaptations

Abstract

Cat-like carnivorans are a textbook example of convergent evolution, with distinct morphological differences between taxa with short or elongated upper canines, the latter often being interpreted as an adaptation to bite at large angles and subdue large prey. This interpretation of the sabre-tooth condition is reinforced by a reduced taxonomic sampling in some studies, often focusing on highly derived taxa or using simplified morphological models. Moreover, most biomechanical analyses focus on biting scenarios at small gapes, ideal for modern carnivora but ill-suited to test for subduction of large prey by sabre-toothed taxa. In this contribution, we present the largest three-dimensional collection-based muscle-induced biting simulations on cat-like carnivorans by running a total of 1074 analyses on 17 different taxa at three different biting angles (30°, 60° and 90°) including both morphologies. While our results show a clear adaptation of extreme sabre-toothed taxa to bite at larger angles in terms of stress distribution, other performance variables display surprising similarities between all forms at the different angles tested, highlighting a continuous rather than bipolar spectrum of hunting methods in cat-like carnivorans and demonstrating a wide functional disparity and nuances of the sabre-tooth condition that cannot simply be characterized by specialized feeding biomechanics.

Conical and sabertoothed cats as an exception to craniofacial evolutionary allometry

“…In particular, variations regarding gape angle, bite force, and bending strength values occurred at fast rates and sabertoothed lineages expanded into different regions of the multivariate trait space. Despite the occurrence of convergent evolution in the craniomandibular morphology of sabertooths 101 , this high functional variability disproved the existence of a single consistent trend towards functional optimization for sabertooth-like morphologies, probably as a consequence of slight differences in hunting/killing strategies resulting in several episodes of ecological niche partitioning within sabertoothed lineages 100 , 102 – 104 (see also Chatar et al 105 for similar considerations concerning mandibular biomechanics).…”

Optimising the flow of mechanical energy in musculoskeletal systems through gearing

“…Even in systems that are “overgeared”, so that instantaneous forcevelocity trade-offs can map onto contraction outcomes as suggested by Arnold et al (Arnold et al 2011), independent variation in geometric variables such as the muscle aspect ratio can result in the mapping of many geometric designs onto the same mechanical performance: musculoskeletal systems with markedly distinct geometries can be physiologically similar (Labonte 2023). Such “many-to-one-mapping” has been identified in an increasing number of mechanical systems (e. g. Alfaro et al 2005; Arnold 1983; Blanke et al 2018; Chatar et al 2022; Moen 2019; Strobbe et al 2009), and can enable morphological and physiological diversification despite a convergence in mechanical function (Muñoz 2019; Muñoz et al 2018; Wainwright 2007; Wainwright et al 2005). Viewed in this light, our warning against an isolated interpretation of G is not a pessimistic negation of the functional significance of G , but an optimistic proposal to re-evaluate the anatomical diversity of musculoskeletal anatomy through the functional interpretation derived from the theory of physiological similarity.…”

Evolutionary Patterns of Cat-Like Carnivorans Unveils Drivers of the Sabertoothed Morphology

“…Saber-toothed taxa are thought to feed on larger prey than similar-sized conical-toothed cats, 6,[9][10][11][12] and a clear dichotomy between the craniomandibular shape of saber-and non-sabertoothed forms was expected based on this assumption. However, recent studies highlight that the functioning of the cat-like mandible 13,14 or even the shape 15 and functioning of the cat-like cranium 16 are more complex than previously expected. Even the assumption that saber-toothed taxa hunted significantly larger prey has been challenged, with some authors suggesting predation on species within a size range similar to those targeted by present-day carnivorans.…”