Abstract
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.
Highlights
The largest amphibians in earth’s history can be found among the capitosaur stereospondyls, a group of temnospondyls that reached body lengths of more than 5 m with large skulls and heavily ossified postcranial skeletons
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; (2) the region lateral to the orbitae is only slightly broader than the orbitae; (3) the postorbital region is slender; (4) the preorbital projection of the jugal is shorter than half the length of the snout
Witzmann et al.: A new species of Cyclotosaurus (Stereospondyli, Capitosauria) fenestrae are represented by an isolated find of Eocyclotosaurus lehmani (E. woschmidti) from the Upper Buntsandstein (Anisian) of Baden-Württemberg (Ortlam, 1970) as well as different species of the genus Cyclotosaurus, known from the middle Carnian (?upper Ladinian) to the late Norian (Schoch and Milner, 2000)
Summary
The largest amphibians in earth’s history can be found among the capitosaur stereospondyls, a group of temnospondyls that reached body lengths of more than 5 m with large skulls and heavily ossified postcranial skeletons. The specimens from Melle were illustrated by neither Römer (1857) nor by von der Marck (1892) and Dienemann (1928, 1939) and it can not be stated whether they belonged to the skull or the dermal pectoral girdle. They were part of the Oberbergrat Jugler collection and are believed to be lost. The find was brought to the Staatliches Museum für Naturkunde in Stuttgart, Germany, where it was prepared It became part of the collection of the Museum of Natural History in Bielefeld and was assigned to Cyclotosaurus robustus. Because of the unique combination of characters present in the Bielefeld specimen, we erect a new species, Cyclotosaurus buechneri sp. nov
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