Articles | Volume 19, issue 2
Foss. Rec., 19, 83–100, 2016
Foss. Rec., 19, 83–100, 2016

Research article 23 Mar 2016

Research article | 23 Mar 2016

A new species of Cyclotosaurus (Stereospondyli, Capitosauria) from the Late Triassic of Bielefeld, NW Germany, and the intrarelationships of the genus

Florian Witzmann1,2, Sven Sachs3,a, and Christian J. Nyhuis4 Florian Witzmann et al.
  • 1Department of Ecology and Evolutionary Biology, Brown University, Providence, G-B204, RI 02912, USA
  • 2Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115 Berlin, Germany
  • 3Naturkundemuseum Bielefeld, Abteilung Geowissenschaften, Adenauerplatz 2, 33602 Bielefeld, Germany
  • 4Galileo-Wissenswelt, Mummendorferweg 11b, 23769 Burg auf Fehmarn, Germany
  • aprivate address: Im Hof 9, 51766 Engelskirchen, Germany

Abstract. A nearly complete dermal skull roof of a capitosaur stereospondyl with closed otic fenestrae from the middle Carnian Stuttgart Formation (Late Triassic) of Bielefeld-Sieker (NW Germany) is described. The specimen is assigned to the genus Cyclotosaurus based on the limited contribution of the frontal to the orbital margin via narrow lateral processes. A new species, Cyclotosaurus buechneri sp. nov., is erected based upon the following unique combination of characters: (1) the interorbital distance is short so that the orbitae are medially placed (shared with C. robustus); (2) the region lateral to the orbitae is only slightly broader than the orbitae (shared with C. posthumus, C. ebrachensis, C. intermedius, and C. mordax); (3) the postorbital region is slender (shared with C. ebrachensis); (4) the preorbital projection of the jugal is shorter than half the length of the snout (shared with C. mordax, C. ebrachensis, C. intermedius, C. posthumus, and C. hemprichi). A phylogenetic analysis of seven Cyclotosaurus species, including C. buechneri, and eight further capitosaur taxa with the Rhinesuchidae as an outgroup finds a monophyletic Cyclotosaurus. In accordance with its stratigraphic occurrence, C. buechneri nests at its base but is more derived than C. robustus. Among the more derived Cyclotosaurus species, C. ebrachensis and C. intermedius, as well as C. posthumus and C. hemprichi, form sister groups, respectively. However, the phylogenetic position of C. mordax with respect to both groups remains unresolved. In the phylogenetic analysis presented here, Cyclotosaurus is the sister group of the Heylerosaurinae (Eocyclotosaurus + Quasicyclotosaurus). Cyclotosaurus buechneri represents the only unequivocal evidence of Cyclotosaurus (and of a cyclotosaur in general) in northern Germany.

Short summary
In this study, the well-preserved skull of a giant amphibian from the Late Triassic Stuttgart Formation (Schilfsandstein) of Bielefeld-Sieker in NW Germany is described and a new species, Cyclotosaurus buechneri sp. nov., is erected. Cyclotosaurus buechneri represents the only unequivocal evidence of Cyclotosaurus in northern Germany. The amphibian skull was found more than 40 years ago and is well known in Bielefeld and the surrounding areas but has so far never been described.