Gronausaurus
- Bückeberg Formation ( Germany )
- Gronausaurus wegneri Hampe, 2013
Gronausaurus is a genus of plesiosaur ( Plesiosauria ). The approximately 3 m long single representatives of their kind, Gronausaurus wegneri, lived in the early Cretaceous ( 139.3 mya ) in the northwestern Thethys. The fossil material on which is based the genus comes from the Bückeberg formation in northwest Germany, where it was found in 1910 in a brick pit. The genus was first described in 2013 by Oliver Hampe and placed on the basis of a phylogenetic analysis of the skeletal elements in the Leptocleididae.
Features
Gronausaurus wegneri was a relatively small plesiosaur of approximately 3 m in length. His skeleton is characterized by several diagnostic features. Thus, the sides of the parasphenoid terminate short of the tubers on the bottom of eye sockets. The vertebral bodies of the kind are easily procoel, so the front side concave and convex behind each other. The second to fourth thoracic vertebra and the anterior dorsal vertebrae exhibit below the lateral spinous fossae on. They probably served as stabilization against train movements Musculi rotatores et levatores. The humerus has at its distal end to a point of contact for a third bone of the forearm, total are all epipodialen (ie to the forearm and shin related ) elements longer than wide.
Fossil material, distribution and stratigraphy
The only fossil specimen of Gronausaurus, a partial skeleton preserved with skull fragments, vertebrae, ribs, bits and pieces of the locomotory apparatus, was found in 1912 in a brick pit near Gronau. The locality was in the early Cretaceous of the northwestern Tethys and lay in a shallow shelf sea. Today it is part of Bückeberg lineup, the age of discovery layer ( 139.3 mya ) dated to the outgoing Berriasian.
Ecology
In the same locality as Gronausaurus different Haigattungen ( Hybodus, Egertonodus, Lonchidion, Lissodus ), the arch -finned Caturus, bone fish Lepidotes that Pycnodontiformen Coelodus and Sphaerodus and Pholidophoriformen Ionoscopus and Callopterus were found. In addition, the turtle Desmemys bertels manni, the dinosaurs Hylaeosaurus and a crocodile tooth have survived. The occurrence of Corbula shells in the Fuschschicht indicates a brackish environment.
System
The skeleton found in 1912 initially attracted little attention among paleontologists. Theodore Wegner examined the skeleton and noticed volatile 1914 that the fossil having significant differences for Brancasaurus simultaneously found in Gronau, but went on an unspecified. Paul Siegfried put it in 1961, in a study in 1912 also Brancasaurus found in Gronau, in the result, it remained under the inventory number GMM A3B.2 at the geological museum of Münster. Only at the beginning of the 21st century was Oliver Hampe bring the fossils to the Natural History Museum in Berlin and she underwent a revision there. Although he recognized a similarity of instance to Brancasaurus, but stressed that it made the differences in skeletal necessary to provide the examined piece in its own genus. He erected the genus Gronausaurus with the way Gronausaurus wegneri for fossils. The genus name means " Gronau lizard" and refers to the locality, the species name honors Theodore Wegner.
A phylogenetic analysis, which undertook Hampe, Gronausaurus pointed out as the sister taxon of Brancasaurus and situate both within the Leptocleididae. Thus originate the genera of Late Jurassic radiation of Cryptoclidia.