Digging adaptation in insectivorous subterranean eutherians. The enigma ofMesoscalops montanensisunveiled by geometric morphometrics and finite element analysis

Abstract

The enigmatic Early Miocene fossorial mammal Mesoscalops montanensis shows one of the most modified humeri among terrestrial mammals. It has been suggested, on qualitative considerations, that this species has no extant homologues for humerus kinematics and that, functionally, the closest extant group is represented by Chrysochloridae. We combine here three dimensional geometric morphometrics, finite element analysis and phylogenetic comparative methods to explore the shape and mechanical stress states of Mesoscalops montanensis as well as of extant and extinct Talpidae and Chrysochloridae under realistic digging simulations. Evolutionary convergence analyses reveal that the shape of Mesoscalops montanensis represents a unique morphology in the context of fossorial mammals and that its functional performance, albeit superficially similar to that of extant Chrysochloridae, still represents a nonconvergent optimum for adaptation to digging.

Talpa fossilis or Talpa europaea? Using geometric morphometrics and allometric trajectories of humeral moles remains from Hungary to answer a taxonomic debate

“…In this case we would expect to find very similar static allometric trajectories, as predicted by the allometric-constraint theory (Voje and Hansen, 2013;Firmat et al, 2014;Voje et al, 2014). The humerus of highly fossorial moles experienced a strong phenotypical channeling in order to adapt to the underground environment (Nevo, 1979;Sán-chez-Villagra et al, 2006;Piras et al, 2012Piras et al, , 2015. The absence of a climatic influence on humeral shape, related to the climatic stability of the subterranean ecotope (Nevo, 1979), supports the evidence that the different allometric slopes likely indicate the presence of two separate species.…”

“…In particular, T. europaea has a larger teres tubercle and pectoral ridge than T. fossilis. In these humeral regions two of the main muscles associated with the burrowing motion are inserted ( Figure 2.2) (Gambaryan et al, 2003;Piras et al, 2012Piras et al, , 2015. On the teres tubercle the Teres major and Latissimus dorsi muscles are inserted, while on the pectoral ridge the Pectoralis Pars Sternalis muscle inserts (Dobson, 1882;Freeman, 1886;Gambaryan et al, 2003).…”

Adaptive evolution of a derived radius morphology in manakins (Aves, Pipridae) to support acrobatic display behavior

“…Our main analysis involved micro-CT scans of the manakins and cotinga. Similar to previous work in this field, we sampled one individual per species (Bostwick et al, 2012;Bird et al, 2014;Van Valkenburgh et al, 2004;Eastman et al, 2014;Crumpton et al, 2015;Piras et al, 2015;Qu et al, 2015;Sentoku et al, 2015;Sharp, 2015). Scans were performed in a General Electric Phoenix Nanotom S Nano-CT scanner.…”

Variation in the shape and mechanical performance of the lower jaws in ceratopsid dinosaurs (Ornithischia, Ceratopsia)

“…A 2D solid geometry was used to study the mechanical behavior of the lower jaws by means of FEA. FEA is a popular mathematical tool among morphologists and vertebrate bio-mechanists to evaluate the strain and stress state within a solid, given its material properties, and under the actions of appropriate loads and constraints that represent a particular functional or behavioral scenario (McHenry et al 2007;Rayfield, 2007Rayfield, , 2011Farke, 2008;Snively & Cox, 2008;Slater & Van Valkenburgh, 2009;Farke et al 2010;Young et al 2010;Tseng et al 2011;Piras et al 2012Piras et al , 2013Piras et al , 2015.…”