Built to Bite: Feeding Kinematics, Bite Forces, and Head Shape of a Specialized<scp>D</scp>urophagous Lizard,<i><scp>D</scp>racaena Guianensis</i>(<scp>T</scp>eiidae)

Schaerlaeken, Vicky; Holanova, Veronika; Boistel, Renaud; Aerts, Peter; Velenský, Petr; Rehák, Ivan; Andrade, Denis V.; Herrel, Anthony

doi:10.1002/jez.1730

Cited by 33 publications

(34 citation statements)

References 37 publications

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“…Counter-intuitively, crocodylians do not display the typical morphology of other hard-biting tetrapods such as tegu lizards, hyenas or Tyrannosaurus, in which the skull is dorsally heightened, expanding the attachment area of temporal muscles and resisting dorsoventral bending of the rostrum (Molnar, 1998;Metzger and Herrel, 2005;Tseng and Stynder, 2011;Schaerlaeken et al, 2012). Instead, crocodylians evolved a dorsoventrally flattened skull, which is hypothesized to be an adaptation for aquatic ambush predation (Iordansky, 1973).…”

Section: Introductionmentioning

confidence: 99%

Ontogeny of bite force in a validated biomechanical model of the American alligator

Sellers

Middleton

Davis

et al. 2017

Journal of Experimental Biology

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Three-dimensional computational modeling offers tools with which to investigate forces experienced by the skull during feeding and other behaviors. American alligators (Alligator mississippiensis) generate some of the highest measured bite forces among extant tetrapods. A concomitant increase in bite force accompanies ontogenetic increases in body mass, which has been linked with dietary changes as animals increase in size. Because the flattened skull of crocodylians has substantial mediolaterally oriented muscles, crocodylians are an excellent model taxon in which to explore the role of mediolateral force components experienced by the feeding apparatus. Many previous modeling studies of archosaur cranial function focused on planar analysis, ignoring the mediolateral aspects of cranial forces. Here, we used three-dimensionally accurate anatomical data to resolve 3D muscle forces. Using dissection, imaging and computational techniques, we developed lever and finite element models of an ontogenetic series of alligators to test the effects of size and shape on cranial loading and compared estimated bite forces with those previously measured in vivo in A. mississippiensis. We found that modeled forces matched in vivo data well for intermediately sized individuals, and somewhat overestimated force in smaller specimens and underestimated force in larger specimens, suggesting that ontogenetically static muscular parameters and bony attachment sites alone cannot account for all the variation in bite force. Adding aponeurotic muscle attachments would likely improve force predictions, but such data are challenging to model and integrate into analyses of extant taxa and are generally unpreserved in fossils. We conclude that anatomically accurate modeling of muscles can be coupled with finite element and lever analyses to produce reliable, reasonably accurate estimate bite forces and thus both skeletal and joint loading, with known sources of error, which can be applied to extinct taxa.

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Section: Introductionmentioning

confidence: 99%

Ontogeny of bite force in a validated biomechanical model of the American alligator

Sellers

Middleton

Davis

et al. 2017

Journal of Experimental Biology

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“…, ), durophagous (Dalrymple, ; Herrel & Holanova, ; Schaerlaeken et al. ) and myrmecophagous species (Montanucci, ; Meyers & Herrel, ; Meyers et al. ) have revealed both morphological and functional changes associated with dietary specialization.…”

Section: Introductionmentioning

confidence: 99%

The evolution of bite force in horned lizards: the influence of dietary specialization

Meyers

Nishikawa

Herrel³

2017

Journal of Anatomy

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Dietary specialization is an important driver of the morphology and performance of the feeding system in many organisms, yet the evolution of phenotypic specialization has only rarely been examined within a species complex. Horned lizards are considered primarily myrmecophagous (ant eating), but variation in diet among the 17 species of horned lizards (Phrynosoma) makes them an ideal group to examine the relationship between dietary specialization and the resultant morphological and functional changes of the feeding system. In this study, we perform a detailed analysis of the jaw adductor musculature and use a biomechanical model validated with in vivo bite force data to examine the evolution of bite force in Phrynosoma. Our model simulations demonstrate that bite force varies predictably with respect to the gape angle and bite position along the tooth row, with maximal bite forces being attained at lower gape angles and at the posterior tooth positions. Maximal bite forces vary considerably among horned lizards, with highly myrmecophagous species exhibiting very low bite forces. In contrast, members of the short-horned lizard clade are able to bite considerably harder than even closely related dietary generalists. This group appears to be built for performing crushing bites and may represent a divergent morphology adapted for eating hard prey items. The evolutionary loss of processing morphology (teeth, jaw and muscle reduction) and bite force in ant specialists may be a response to the lack of prey processing rather than a functional adaptation per se.

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“…The hypothetical model proposed for adult V. niloticus is actually witnessed in durophagous teiids such as Dracaena and Tupinambis (Conant, ; Rand, ; Schaerlaeken et al. ). Their craniodental adaptations of durophagy are superficially similar to the condition found in V. niloticus , including distal molariform teeth and a concave mandible (MacLean, ; Presch, ; Dalrymple, ).…”

Section: Discussionmentioning

confidence: 99%

Illustrating ontogenetic change in the dentition of theNile monitor lizard,Varanus niloticus: a case study in the application of geometric morphometric methods for the quantification of shape–size heterodonty

D’Amore

2015

Journal of Anatomy

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Many recent attempts have been made to quantify heterodonty in non-mammalian vertebrates, but the majority of these are limited to Euclidian measurements. One taxon frequently investigated is Varanus niloticus, the Nile monitor. Juveniles possess elongate, pointed teeth (caniniform) along the entirety of the dental arcade, whereas adults develop large, bulbous distal teeth (molariform). The purpose of this study was to present a geometric morphometric method to quantify V. niloticus heterodonty through ontogeny that may be applied to other non-mammalian taxa. Data were collected from the entire tooth row of 19 dry skull specimens. A semilandmark analysis was conducted on the outline of the photographed teeth, and size and shape were derived. Width was also measured with calipers. From these measures, sample ranges and allometric functions were created using multivariate statistical analyses for each tooth position separately, as well as overall measures of heterodonty for each specimen based on morphological disparity. The results confirm and expand upon previous studies, showing measurable shape-size heterodonty in the species with significant differences at each tooth position. Tooth size increases with body size at most positions, and the allometric coefficient increases at more distal positions. Width shows a dramatic increase at the distal positions with ontogeny, often displaying pronounced positive allometry. Dental shape varied in two noticeable ways, with the first composing the vast majority of shape variance: (i) caniniformy vs. molariformy and (ii) mesially leaning, 'rounded' apices vs. distally leaning, 'pointed' apices. The latter was twice as influential in the mandible, a consequence of host bone shape. Mesial teeth show no significant shape change with growth, whereas distal teeth change significantly due primarily to an increase in molariformy. Overall, heterodonty increases with body size concerning both tooth size and shape, but shape heterodonty changes in the mandible are much less pronounced. Although it is unclear to what degree V. niloticus specializes in hard prey items (durophagy), previous studies of varanid feeding behavior, along with research on analogous durophagous vertebrates, indicate a division of labor along the tooth row in adults, due to a possible transition to at least a partial durophagous niche. The geometric morphometric method proposed here, although not without its own limitations, may be ideal for use with a number of dental morphotypes in the future.

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Built to Bite: Feeding Kinematics, Bite Forces, and Head Shape of a SpecializedDurophagous Lizard,Dracaena Guianensis(Teiidae)

Cited by 33 publications

References 37 publications

Ontogeny of bite force in a validated biomechanical model of the American alligator

Ontogeny of bite force in a validated biomechanical model of the American alligator

The evolution of bite force in horned lizards: the influence of dietary specialization

Illustrating ontogenetic change in the dentition of theNile monitor lizard,Varanus niloticus: a case study in the application of geometric morphometric methods for the quantification of shape–size heterodonty

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