A new basal sphenacodontid synapsid, represented by an anterior portion of a mandible, demonstrates for the first time the presence of amniotes in the largest European Permo−Carboniferous basin, the Saar−Nahe Basin. The new taxon, Cryptovenator hirschbergeri gen. et sp. nov., is autapomorphic in the extreme shortness and robustness of the lower jaw, with moderate heterodonty, including the absence of a greatly reduced first tooth and only a slight caniniform development of the second and third teeth. Cryptovenator shares with Dimetrodon, Sphenacodon, and Ctenospondylus, but notably not with Secodontosaurus, enlarged canines and a characteristic teardrop outline of the marginal teeth in lateral view, possession of a deep symphyseal region, and a strongly concave dorsal margin of the dentary. The new find shows that sphenacodontids were present in the Saar−Nahe Basin by the latest Carboniferous, predating the record of sphenacodontid tracks from slightly younger sediments in this region.

Key words: Synapsida, Sphenacodontidae, Carboniferous, Saar-Nahe Basin, Germany.

Jörg Fröbisch [jfrobisch@fieldmuseum.org], Department of Geology, The Field Museum, 1400 South Lake Shore Drive, Chicago, Illinois 60605, USA and and [joerg.froebisch@mfn−berlin.de], Museum für Naturkunde Leibniz−Institut für Evolutions− und Biodiversitätsforschung an der Humboldt−Universität zu Berlin, Invalidenstr. 43, D−10115 Berlin, Germany; Rainer R. Schoch [schoch.smns@naturkundemuseum-bw.de], Staatliches Museum für Naturkunde, Rosenstein 1, D-70191 Stuttgart, Germany; Johannes Müller [johannes.mueller@mfn-berlin.de], Museum für Naturkunde – Leibniz-Institut für Evolutions- und Biodiversitätsforschung an der Humboldt-Universität zu Berlin, Invalidenstr. 43, D-10115 Berlin, Germany; Thomas Schindler [psg.t.schindler@t-online.de], Büro für Paläontologie, Stratigraphie und Geotopschutz, Am Wald 11, D-55595 Spabrücken, Germany; Dieter Schweiss [dj.schweiss@t-online.de], Geoskop Urweltmuseum, Burg Lichtenberg, D-66871 Thallichtenberg, Germany.