title: The remarkable convergence of skull shape in crocodilians and toothed whales.
abstract: The striking resemblance of long-snouted aquatic mammals and reptiles has long been considered an example of morphological convergence, yet the true cause of this similarity remains untested. We addressed this deficit through three-dimensional morphometric analysis of the full diversity of crocodilian and toothed whale (Odontoceti) skull shapes. Our focus on biomechanically important aspects of shape allowed us to overcome difficulties involved in comparing mammals and reptiles, which have fundamental differences in the number and position of skull bones. We examined whether diet, habitat and prey size correlated with skull shape using phylogenetically informed statistical procedures. Crocodilians and toothed whales have a similar range of skull shapes, varying from extremely short and broad to extremely elongate. This spectrum of shapes represented more of the total variation in our dataset than between phylogenetic groups. The most elongate species (river dolphins and gharials) are extremely convergent in skull shape, clustering outside of the range of the other taxa. Our results suggest the remarkable convergence between long-snouted river dolphins and gharials is driven by diet rather than physical factors intrinsic to riverine environments. Despite diverging approximately 288 million years ago, crocodilians and odontocetes have evolved a remarkably similar morphological solution to feeding on similar prey.
authors.affiliation: Monash Biomedicine Discovery Institute and Centre for Human Anatomy Education, Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia m.r.mccurry1@gmail.com.|Geosciences, Museums Victoria, Melbourne, VIC, Australia.|Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
authors.forename: Matthew R
authors.identifier: http://orcid.org/0000-0002-2452-1404
authors.initials: MR
authors.lastname: McCurry
authors.affiliation: School of Biological Sciences, Monash University, Melbourne, VIC, Australia.|Geosciences, Museums Victoria, Melbourne, VIC, Australia.
authors.forename: Alistair R
authors.initials: AR
authors.lastname: Evans
authors.affiliation: Geosciences, Museums Victoria, Melbourne, VIC, Australia.|Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.|Department of Life Sciences, Natural History Museum, London, UK.
authors.forename: Erich M G
authors.initials: EM
authors.lastname: Fitzgerald
authors.affiliation: Monash Biomedicine Discovery Institute and Centre for Human Anatomy Education, Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia.
authors.forename: Justin W
authors.initials: JW
authors.lastname: Adams
authors.affiliation: School of Engineering, University of Newcastle, Newcastle, NSW, Australia.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Clausen
authors.affiliation: Monash Biomedicine Discovery Institute and Centre for Human Anatomy Education, Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia.|School of Engineering, University of Newcastle, Newcastle, NSW, Australia.|School of Life and Environmental Science, University of Newcastle, Newcastle, NSW, Australia.
authors.forename: Colin R
authors.initials: CR
authors.lastname: McHenry
mesh_terms: D000489:Alligators and Crocodiles / Q000033:anatomy & histology*; D000818:Animals; D010802:Phylogeny; D012886:Skull / Q000033:anatomy & histology*; D014907:Whales / Q000033:anatomy & histology*
keywords: Crocodilia; Odontoceti; crania; ecomorphology; feeding; rostra