Fossil Record 18(1): 17-30, doi: 10.5194/fr-18-17-2015
New information on the cranial and postcranial anatomy of the early synapsid Ianthodon schultzei (Sphenacomorpha: Sphenacodontia), and its evolutionary significance
expand article infoF. Spindler, D. Scott§, R. R. Reisz|
‡ TU Bergakademie Freiberg, Institut für Geologie, Bernhard-von-Cotta-Straße 2, 09599 Freiberg, Germany§ Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, Ontario, L5L 1C6, Canada| Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Road N, Mississauga, ON L5L 1C6, Canada
Open Access
Newly identified material belonging to the holotype specimen of Ianthodon schultzeisubstantially increases our knowledge of this poorly known basalsphenacodont synapsid from the fossil site in Garnett, Kansas (Missourian, LatePennsylvanian). The original description, based on a partial dermal skullroof, is augmented with information on the palate and braincase, togetherwith data on the mandible and a few postcranial elements. The known skeletalmorphology resembles that of Haptodus garnettensis, another synapsid taxon known from thislocality, but with fewer marginal, distinctly recurved teeth and smallerteeth on the transverse flange of the pterygoid. Although recognizing thatthe holotype and only known specimen represents a juvenile individual,Ianthodon appears to reflect a more basal sphenacodontian condition than H. garnettensis. Arestricted phylogenetic analysis based on previous work and newly scoredcharacters for Ianthodon, Cutleria and Pantelosaurus supports this hypothesis. The Garnett localityappears to preserve an assemblage of synapsids (Haptodus, Ianthasaurus, Ianthodon) that are close to the baseof the large clade that includes Edaphosauridae and Sphenacodontia,suggesting that an initial diversification of this clade occurred well within theCarboniferous Period.