Evolutionary Biomechanics

Water collection and drinking in Phrynocephalus helioscopus: a possible condensation mechanism

by Kurt Schwenk

A simple, inexpensive system for digital particle image velocimetry (DPIV) in biomechanics

by Kurt Schwenk

Van der Meijden, A., T. Kleinteich, P. Coelho (In Press) Packing a pinch; Functional implications of chela shapes in scorpions using finite element analysis. Journal of Anatomy.

by Arie van der Meijden

Scorpions depend on their pedipalps for prey capture, defense, mating and sensing their environment. Some species... more Scorpions depend on their pedipalps for prey capture, defense, mating and sensing their environment. Some species additionally use their pedipalps for burrowing or climbing. Because the pincers or chelae at the end of the pedipalps vary widely in shape, they have been used as part of a suite of characters to delimit ecomorphotypes. We here evaluate the influence of the different chela cuticular shapes on their performance under natural loading conditions. Chelae of 20 species, representing seven families and spanning most of the range of chela morphologies, were assigned to clusters based on chela shape parameters using hierarchical cluster analysis. Several clusters were identified corresponding approximately to described scorpion ecomorphotypes. Finite element models of the chela cuticulae were constructed from CT scans and loaded with estimated pinch forces based on in vivo force measurements. Chela shape clusters differed significantly in mean Von Mises stress and strain energy. Normalized FEA showed that chela shape significantly influenced Von Mises stress and strain energy in the chela cuticula, with Von Mises stress varying up to an order of magnitude and strain energy up to two orders of magnitude. More elongate, high-aspect ratio chela forms showed significantly higher mean stress compared with more robust low-aspect ratio forms. This suggests that elongate chelae are at a higher risk of failure when operating near the maximum pinch force. Phylogenetic independent contrasts (PIC) were calculated based on a partly resolved phylogram with branch lengths based on an alignment of the 12S, 16S and CO1 mitochondrial genes. PIC showed that cuticular stress and strain in the chela were correlated with several shape parameters, such as aspect ratio, movable finger length, and chela height, independently of phylogenetic history. Our results indicate that slender chela morphologies may be less suitable for high-force functions such as burrowing and defense. Further implications of these findings for the ecology and evolution of the different chela morphologies are discussed.

In vivo bone strain and finite‐element modeling of the craniofacial haft in catarrhine primates

by Callum Ross

Ross, C. F., Berthaume, M., Iriarte-Diaz, J. Dechow, P. C., Porro, L.B., Richmond, B. G., Spencer, M. and Strait, D. (2011) In vivo bone strain and finite-element modeling of the craniofacial haft in catarrhine primates. Journal of Anatomy 218: 112-141.

The evolution of cranial design and performance in squamates: consequences of skull-bone reduction on feeding behavior

by Callum Ross

Herrel, A., Schaerlaeken, V., Meyers, J.J., Metzger, K.A., and Ross, C.F. (2007) The evolution of cranial design and performance in squamates: consequences of skull bone reduction on feeding behavior. Integrative and Comparative Biology 47:107-117.

Rhythmicity in teleost chewing: A comparison with amniotes.

by Callum Ross

Gintof, C., Konow, N., Ross, C.F., Sanford, C.P.J. (2010) Journal of Experimental Biology 213: 1868-1875.

Chewing variation in lepidosaurs and primates.

by Callum Ross

Ross, C.F., Baden, A.L., Georgi, J.A., Herrel, A., Metzger, K.A., Reed, D.A., Schaerlaeken, V., Wolff, M.S. (2010) Journal of Experimental Biology 213: 572-584.

The evolution of cranial design and performance in squamates: consequences of skull bone reduction on feeding behavior.

by Callum Ross

Herrel, A., Schaerlaeken, V., Meyers, J.J., Metzger, K.A., and Ross, C.F. (2007) Integrative and Comparative Biology 47:107-117.

The functional significance of the lower temporal bar in Sphenodon punctatus.

by Callum Ross

Schaerlaeken, V., Herrel, A., Aerts, P., Ross, C.F. (2008)  Journal of Experimental Biology 211: 3908-3914.

Horned Lizards (Phrynosoma) Incapacitate Dangerous Ant Prey With Mucus

by Kurt Schwenk

The evolution of extreme hypercarnivory in Metriorhynchidae (Mesoeucrocodylia: Thalattosuchia) based on evidence from microscopic denticle morphology

by Mark Young

Journal of Vertebrate Paleontology, 2010

Metriorhynchids were a peculiar group of fully marine Mesozoic crocodylomorphs. The derived genera Dakosaurus and... more Metriorhynchids were a peculiar group of fully marine Mesozoic crocodylomorphs. The derived genera Dakosaurus and Geosaurus exhibit a macroevolutionary trend towards extreme hypercarnivory, underpinned by a diverse array of craniodental adaptations, including denticulate serrated (ziphodont) dentition. A comparative analysis of serrations in Metriorhynchidae shows that known Dakosaurus species had conspicuous denticles, in contrast to the microscopic denticles of Geosaurus. A new tooth from the Nusplingen Plattenkalk of Germany provides evidence for a previously unknown large species of Geosaurus. Metriorhynchid specimens from the upper Kimmeridgian–lower Tithonian of Southern Germany show that ziphodont species of Dakosaurus and Geosaurus co-occurred in the Nusplingen and Solnhofen Seas. Although these genera are similarly denticulate, they diverge in overall crown morphology. Therefore, resource/niche partitioning via craniodental differentiation is posited as maintaining two contemporaneous genera of highly predatory metriorhynchids. Additionally, the new generic name Torvoneustes is proposed for “Geosaurus” carpenteri, the only known metriorhynchid with false-ziphodont dentition. A cladistic analysis shows that ziphodont dentition may have evolved independently in Dakosaurus and Geosaurus, or been acquired earlier by their common ancestor and secondarily lost in Torvoneustes and related taxa.

The evolution of Metriorhynchoidea (Mesoeucrocodylia, Thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics

by Mark Young

Zoological Journal of the Linnean Society, 2010

Metriorhynchoid crocodylians represent the pinnacle of marine specialization within Archosauria. Not only were they a... more Metriorhynchoid crocodylians represent the pinnacle of marine specialization within Archosauria. Not only were they a major component of the Middle Jurassic–Early Cretaceous marine ecosystems, but they provide further examples that extinct crocodilians did not all resemble their modern extant relatives. Here, we use a varied toolkit of techniques, including phylogenetic reconstruction, geometric morphometrics, diversity counts, discrete character disparity analysis, and biomechanical finite-element analysis (FEA), to examine the macroevolutionary history of this clade. All analyses demonstrate that this clade became more divergent, in terms of biodiversity, form, and function, up until the Jurassic–Cretaceous boundary, after which there is no evidence for recovery or further radiations. A clear evolutionary trend towards hypercarnivory in Dakosaurus is supported by phylogenetic character optimization, morphometrics, and FEA, which also support specialized piscivory within Rhacheosaurus and Cricosaurus. Within Metriorhynchoidea, there is a consistent trend towards increasing marine specialization,
with the hypermarine Cricosaurus exhibiting numerous convergences with other Mesozoic marine reptiles (e.g. loss of the deltopectoral crest and retracted external nares). In addition, biomechanics, morphometrics, and character disparity analyses consistently distinguish the two newly erected metriorhynchid subfamilies. This study illustrates that together with phylogeny, quantitative assessment of diversity, form, and function help elucidate the macroevolutionary pattern of fossil clades.

Bite forces and evolutionary adaptations to feeding ecology in carnivores (Ecology)

by Stephen Wroe

Christiansen, P., and Wroe, S. 2007. Bite forces and evolutionary adaptations to feeding ecology in carnivores. Ecology, 88: 347-358

The Carnivora spans the largest ecological and body size diversity of any mammalian order, making it an ideal basis... more The Carnivora spans the largest ecological and body size diversity of any mammalian order, making it an ideal basis for studies of evolutionary ecology and functional morphology. For animals with different feeding ecologies, it may be expected that bite force represents an important evolutionary adaptation, but studies have been constrained by a lack of bite force data. In this study we present predictions of bite forces for 151 species of extant carnivores, comprising representatives from all eight families and the entire size and ecological spectrum within the order. We show that, when normalized for body size, bite forces differ significantly between the various feeding categories. At opposing extremes and independent of genealogy, consumers of tough fibrous plant material and carnivores preying on large prey both have high bite forces for their size, while bite force adjusted for body mass is low among specialized insectivores. Omnivores and carnivores preying on small prey have more moderate bite forces for their size. These findings indicate that differences in bite force represent important adaptations to and indicators of differing feeding ecologies throughout carnivoran evolution. Our results suggest that the incorporation of bite force data may assist in the construction of more robust evolutionary and palaeontological analyses of feeding ecology.