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

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 BielefeldSieker (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.

Cyclotosaurus naraserluki,sp. nov., a new Late Triassic cyclotosaurid (Amphibia, Temnospondyli) from the Fleming Fjord Formation of the Jameson Land Basin (East Greenland)

“…In this study, we provide the first complete anatomical description and phylogenetic analysis of the capitosaurid skull reported in Jenkins et al (1994) and associated vertebral intercentra. We support the original assignment of the Greenlandic specimen to the genus Cyclotosaurus based on the undoubted presence of seven of the eight synapomorphies given for this genus in Witzmann et al (2016). Cyclotosaurus naraserluki is erected as a new species, based on a combination of autapomorphies and associated characters unique among known cyclotosaurids.…”

“…7, 8), with a tree length (TL) of 109 steps and consistency index (CI) of 0.624, retention index (RI) of 0.680, and rescaled consistency index (RCI) of 0.424. Because of the recoding of character 7 and the addition of C. naraserluki, our phylogeny of Cyclotosaurus is slightly different from the one presented in Witzmann et al (2016). Cyclotosaurus loses one synapomorphy (char.…”

“…They meander anteroposteriorly from the nasals to the prefrontals, reaching the posterior part of the frontals, and weakly ending on the postfrontals, at around the midline of the orbits. Regardless of the weak preservation of both lacrimals, the left supraorbital sulcus seems to run along the suture between the prefrontal and the lacrimal, like in other cyclotosaurids and temnospondyls (see Schoch, 2008;Rinehart et al, 2015;Rinehart and Lucas, 2016;Witzmann et al, 2016).…”

“…Cyclotosaurus naraserluki MGUH.VP 9522 was coded in the data set by Witzmann et al (2016) for a total of 17 taxa and 69 characters (Appendix 1). Character 7 of Witzmann et al (2016) was reformulated for the present analysis as character 7: Lateral line sulci: weakly impressed and discontinuous (0); continuous and well impressed (1); well impressed laterally and weakly impressed or discontinuous medially (2). State 2 for character 7 was coded for C. ebrachensis, C. hemprichi, C. mordax, C. naraserluki, C. posthumus, and C. robustus.…”

“…Moreover, at least four synapomorphies are known to identify cyclotosaurids: infraorbital canals curving over the lacrimals with a 'Z' shape, vomerine tusks positioned lateral to the palatal vacuity, a wide parabolic snout, and a vomerine palate as long as wide (Damiani, 2001;Schoch, 2008). Among the largest amphibians to have ever lived (total body length up to 3 m), cyclotosaurids were mostly piscivorous, semi-aquatic predators, colonizing freshwater niches, such as rivers and lakes, as well as coastal brackish to marine areas (Milner, 1994;Fortuny et al, 2016;Witzmann et al, 2016).…”