Fossil Record 19(2): 83-100, doi: 10.5194/fr-19-83-2016
A new species of Cyclotosaurus (Stereospondyli, Capitosauria) from the Late Triassic of Bielefeld, NW Germany, and the intrarelationships of the genus
expand article infoFlorian Witzmann, Sven Sachs§, Christian J. Nyhuis|
‡ Museum für Naturkunde Berlin, Berlin, Germany§ Naturkundemuseum Bielefeld, Abteilung Geowissenschaften, Adenauerplatz 2, 33602 Bielefeld, Germany| Galileo-Wissenswelt, Mummendorferweg 11b, 23769 Burg auf Fehmarn, Germany
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A nearly complete dermal skull roof of a capitosaur stereospondyl withclosed otic fenestrae from the middle Carnian Stuttgart Formation (LateTriassic) of Bielefeld-Sieker (NW Germany) is described. The specimen isassigned to the genus Cyclotosaurus based on the limited contribution of the frontal tothe orbital margin via narrow lateral processes. A new species,Cyclotosaurus buechneri sp. nov., is erected based upon the following unique combination ofcharacters: (1) the interorbital distance is short so that the orbitae aremedially placed (shared with C. robustus); (2) the region lateral to the orbitae isonly slightly broader than the orbitae (shared with C. posthumus, C. ebrachensis, C. intermedius, and C. mordax); (3) thepostorbital region is slender (shared with C. ebrachensis); (4) the preorbital projectionof 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 furthercapitosaur taxa with the Rhinesuchidae as an outgroup finds a monophyleticCyclotosaurus. In accordance with its stratigraphic occurrence, C. buechneri nests at its base but ismore derived than C. robustus. Among the more derived Cyclotosaurus species, C. ebrachensis and C. intermedius, as well as C. posthumus andC. hemprichi, form sister groups, respectively. However, the phylogenetic position of C. mordaxwith respect to both groups remains unresolved. In the phylogenetic analysispresented here, Cyclotosaurus is the sister group of the Heylerosaurinae(Eocyclotosaurus + Quasicyclotosaurus). Cyclotosaurus buechneri represents the only unequivocal evidence of Cyclotosaurus (and of a cyclotosaurin general) in northern Germany.