title: The oldest parareptile and the early diversification of reptiles.
abstract: Amniotes, tetrapods that evolved the cleidoic egg and thus independence from aquatic larval stages, appeared ca 314 Ma during the Coal Age. The rapid diversification of amniotes and other tetrapods over the course of the Late Carboniferous period was recently attributed to the fragmentation of coal-swamp rainforests ca 307 Ma. However, the amniote fossil record during the Carboniferous is relatively sparse, with ca 33% of the diversity represented by single specimens for each species. We describe here a new species of reptilian amniote that was collected from uppermost Carboniferous rocks of Prince Edward Island, Canada. Erpetonyx arsenaultorum gen. et sp. nov. is a new parareptile distinguished by 29 presacral vertebrae and autapomorphies of the carpus. Phylogenetic analyses of parareptiles reveal E. arsenaultorum as the closest relative of bolosaurids. Stratigraphic calibration of our results indicates that parareptiles began their evolutionary radiation before the close of the Carboniferous Period, and that the diversity of end-Carboniferous reptiles is 80% greater than suggested by previous work. Latest Carboniferous reptiles were still half as diverse as synapsid amniotes, a disparity that may be attributable to preservational biases, to collecting biases, to the origin of herbivory in tetrapods or any combination of these factors.
authors.affiliation: Department of Biology, Cape Breton University, Sydney, Nova Scotia, Canada B1P 6L2.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Modesto
authors.affiliation: Department of Biology, University of Toronto at Mississauga, Mississauga, Ontario, Canada L5L 1C6.
authors.forename: Diane M
authors.initials: DM
authors.lastname: Scott
authors.affiliation: Department of Biology, University of Toronto at Mississauga, Mississauga, Ontario, Canada L5L 1C6.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: MacDougall
authors.affiliation: National Museum of Natural History, Smithsonian Institution, MRC 121, PO Box 37012, Washington, DC 20013-7012, USA.
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Sues
authors.affiliation: Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, Canada.
authors.forename: David C
authors.initials: DC
authors.lastname: Evans
authors.affiliation: Department of Biology, University of Toronto at Mississauga, Mississauga, Ontario, Canada L5L 1C6 robert.reisz@utoronto.ca.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Reisz
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005580:Fossils / Q000033:anatomy & histology*; D010163:Paleontology; D010802:Phylogeny; D011325:Prince Edward Island; D012104:Reptiles / Q000033:anatomy & histology* / Q000145:classification*
keywords: carboniferous; diversification; evolution; parareptile