Virtual reconstruction of the Canis arnensis type (Canidae, Mammalia) from the Upper Valdarno Basin (Italy, Early Pleistocene).

Taphonomic deformation, whether it be brittle or plastic, is possibly the most influential process hindering the correct understanding of fossil species morphology. This is especially true if the deformation affects type specimens or applies to or obscures taxonomically diagnostic or functionally significant traits. Target Deformation, a recently developed virtual manipulation protocol, was implemented to address this issue by applying landmark-guided restoration of the original, deformed fossils, using undeformed specimens (or parts thereof) of the same species as a reference. The enigmatic Early Pleistocene canid Canis arnensis provides a typical example of a fossil species in dire need of virtual restoration. Its lectotype specimen is heavily deformed and none of the few known skulls are well preserved, obscuring the recognition of its systematic and phylogenetic position. Our results indicate that the algorithm effectively countered the lectotype skull's laterolateral compression and its concomitant rostrocaudal elongation. Morphometrically, comparison of the retrodeformed cranium (IGF 867_W) with other specimens of the same species, and to other fossil and extant canid material, confirms IGF 867_W consistently clusters within C. arnensis variability. Overall, the evidence presented here confirms that Target Deformation provides a powerful tool to better characterize complex taxa like C. arnensis, whose knowledge is severely affected by the state of preservation of its fossil material.

Habitat changes and changing predatory habits in North American fossil canids.

The spread of open grassy habitats and the evolution of long-legged herbivorous mammals with high-crowned cheek teeth have been viewed as an example of coevolution. Previous studies indicate that specialized predatory techniques in carnivores do not correlate with the spread of open habitats in North America. Here we analyse new data on elbow-joint shape for North American canids over the past ∼37 million years and show that incipiently specialized species first appeared along with the initial spread of open habitats in the late Oligocene. Elbow-joint morphologies indicative of the behavior of modern pounce-pursuit predators emerged by the late Miocene coincident with a shift in plant communities from C3 to C4 grasses. Finally, pursuit canids first emerged during the Pleistocene. Our results indicate that climate change and its impact on vegetation and habitat structure can be critical for the emergence of ecological innovations and can alter the direction of lineage evolution.