A new skeleton of Ianthasaurus hardestii, a primitive edaphosaur (Synapsida: Pelycosauria) from the Upper Pennsylvanian of Kansas S. P. MODESTO AND R. R. REISZ Department of Zoology, Erindale Campus, University of Toronto, Mississauga, Ont., Canada L5L lC6 Received September 11, 1989 Revision accepted February 7, 1990 A new specimen from the Upper Pennsylvanian of Garnett, Kansas, is referable to the edaphosaur Ianthasaurus hardestii.It is the second articulated skeleton known of this species, and possesses previously undescribed midline elements of the skull roof. This specimen features a new autapomorphy, an elongate cross-barred dorsal process on the axial neural spine. The presence of ventral webbing and multiple tubercles on several basal lateral protuberances of the presacral neural spines in this skeleton may represent a sexual dimorphism of lanthasaurus. Two synapomorphies of sphenacodonts and edaphosaurs, the presence of a lateral lappet on the frontal and exclusion of the reduced quadratojugal from the ventral margin of the temporal bar, are confirmed in this specimen. The presence of these traits in Ianthasaurus supports the hypothesis that edaphosaurs and sphenacodonts form a clade more derived than other pelycosaur groups. New information provided by this specimen indicates that edaphosaurs can be recognized only by the morphology of their distinctive presacral neural spines. Small, problematical edaphosaur species assigned to the genus Edaphosaurus may be reinterpreted as insectivores, closely related to the Garnett edaphosaur and distinguishable from the large, bulky herbivore Edaphosaurus. Un nouveau spCcimen du site Garnett (Pennsylvanien superieur) est assign6 A 1'Cdaphosaure Ianthasaurus hardestii. I1 s'agit du second squelette articulC connu de cet Cdaphosaure. Ce squelette possbde des ClCments mCdians du toit cranien non prCsemCs dans l'autre sp6cimen de ce genre. Ce specimen dCmontre la prksence d'une nouvelle autapomorphie : I'tpine neurale axiale possbde un processus transverse dorsal allongC. La prksence d'une palmure ventrale et de tubercules multiples sur plusieurs protubCrances IatCrales proximales des vertbbres prtsacrCes indiquent peut-Ctre un dimorphisme sexuel. L'existence de deux synapomorphies des sphtnacodontes et des Cdaphosaures, la prCsence d'un processus literal du frontal et I'exclusion du quadratojugal du bord ventral de l'arc temporal, est confirmke par ce spCcimen. L'Cdaphosaure de Garnett possbde des caractbes qui supportent I'hypothbe selon laqulle les Cdaphosaures et les sphCnacodontes foment un clade plus dCrivC que les autres p6lycosaures. Ce nouveau spCcimen indique que 1'Edaphosauridae peut &tre dCfinie seulement par la morphologie de leurs Cpines neurales prksacrkes. Les petites espbces d'edaphosaures d'affinitks incertaines qui avaient CtC assignCes au genre Edaphosaurus peuvent &tre rkinterprktkes comrne Ctant des insectivores Ctroitement apparentis B 1'Cdaphosaure de Garnett et distincts du grand herbivore Edaphosaurus. Can. J. Earth Sci. 27, 834-844 (1990) Introduction The pelycosaur family Edaphosauridae, represented by the genera Edaphosaurus and Ianthasaurus, spans the Upper Pennsylvanian and the Lower Permian strata of Europe and North America. Edaphosaurus is one of the most widespread and successful of Permian reptiles. Eight species are currently recognized (Reisz 1986). Dental morphology indicates that Edaphosaurus probably fed upon plant material. The majority of differences between Edaphosaurus and Ianthasaurus are directly attribut- able to this adaptation to herbivory: large body size, barrel- shaped trunk, relatively small skull, enlarged temporal fenes- trae, slightly bulbous marginal dentition, and massive crushing tooth plates on the palate and the medial surface of the mandible. Edaphosaurus is adequately represented by five North American species, four of these by cranial as well as postcranial material. In the absence of adequate specimens, the validity of two small European and a small North American species has been questioned by Reisz (1986). Ianthasaurus, the smaller, earlier, and morphologically more primitive member of the Edaphosauridae, is known from a single species from the Upper Pennsylvanian of Kansas. Ianthasaurus is distinguished from later edaphosaurs by its small body and dorsal-sail size, slim trunk, relatively large skull, small temporal fenestrae, long and low maxillae with sharp, recurved teeth, caniniform teeth, and no tooth plates (Reisz and Berman 1986). On the basis of the morphology of its marginal and inferred palatal dentition, Reisz and Berman (1986) suggested that this edaphosaur fed primarily upon soft-bodied insects. The small, elongate body, large head, and small temporal openings support this hypothesis. Therefore, Ianthasaurus differs from Edaphosaurus essentially in its adaptation to insectivory. The description of Ianthasaurus hardestii (Reisz and Berman 1986) was based solely on material from Garnett, Kansas. The Garnett locality has produced an abundance of vertebrate, inver- tebrate, and plant remains, including taxa of great phylogenetic significance such as the oldest known diapsid Petrolacosaurus kansensis (Reisz 1977, 198I), the earliest sphenacodont Hap- todus garnettensis (Currie 1977), and other unique, endemic arnniote species (Reisz et al. 1982; Dilkes 1987). The speci- mens available to Reisz and Berman (1986) depicted a very primitive eupelycosaur with a single autapomorphy, the pres- ence of at least 29 presacral vertebrae. The holotype also characterized Ianthasaurus as bearing a maximum of five pairs of lateral tubercles on each neural spine, with crossbars concentrated on the anterior two thirds of the sail. However, the palate, braincase, occiput, most of the skull table, and much of the pectoral girdle were absent from the known specimens or, in the case of the limb elements, too poorly preserved for descriptive purposes. The description of the Garnett edaphosaur appeared soon after recent reevaluations of pelycosaur interrelationships. Brinkman and Eberth (1983) showed that the Edaphosauridae and the Sphenacodontidae form a clade defined by several synapomorphies. Reisz and Berman (1986) demonstrated that Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by Renmin University of China on 06/04/13 For personal use only.