Arminisaurus
| Arminisaurus | ||||||||||
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Arminisaurus skeleton, Bielefeld Natural History Museum |
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| Temporal occurrence | ||||||||||
| Lower Jurassic (Upper Pliensbachian ) | ||||||||||
| 187.5 to 182.7 million years | ||||||||||
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| Scientific name | ||||||||||
| Arminisaurus | ||||||||||
| Sachs & Kear , 2017 | ||||||||||
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Arminisaurus is a genus of plesiosaurs from the Pliosauridae family thatlivedin what is now Germany during the early Jurassic period. The only species is Arminisaurus schuberti . The genus is, after Westphaliasaurus and Cryonectes , only the third plesiosaur, which was named from the level of Pliensbachium (190.8-182.7 mya ). The holotype and the only known specimen of Arminisaurus schuberti is an incomplete skeleton (about 40% have been preserved), which includes part of the lower jaw, teeth, vertebrae and bones from the chest girdle and extremities. The body length was estimated at 3–4 m.
discovery
The holotype was discovered in the early 1980s by the Hanoverian fossil collector Lothar Schulz in the now disused Beukenhorst II clay pit in the Jöllenbeck district of Bielefeld . The find layer belongs to the Amaltheenton formation of the upper Pliensbachian ( Amaltheus margaritatus -Ammonite zone). The specimen later came into the possession of the Steinhagen amateur paleontologist Siegfried Schubert, who handed the find over to the Bielefeld Natural History Museum in 2015 . Here the holotype is inventoried under the copy number NAMU ES / jl 36052.
Naming
Arminisaurus schuberti was in 2017 by Sven Sachs and Benjamin Kear described . The generic name Arminisaurus refers to the Cheruscan prince Arminius and pays homage to the region in which the fossil was found. The species name schuberti honors Siegfried Schubert, who through his publications (including various scientific papers) has expanded our knowledge of the geological conditions in the Bielefeld region.
Anatomical features
Arminisaurus schuberti has a combination of anatomical features that is unique within the plesiosaurs. Among other things, a striking notch is formed at the rear end of the joint socket of the lower jaw and the lateral area of the lower jaw is not dented in front of the joint socket as is usual for other plesiosaurs of this group. The cervical vertebrae have small thorn-like protrusions, so-called parazygapophyseal processes, as well as strongly concave joint surfaces. The shoulder blade is not rod-shaped and thickened in the middle, as in other plesiosaurs of the Lower Jurassic, but rather thin. In addition, the shoulder blade has a distinctive keel on the lower outside.
Taxonomy
In a phylogenetic analysis, Arminisaurus schuberti was recognized as a member of the Pliosauridae family, a globally widespread clade within the plesiosaurs, which is documented from the Lower Jurassic to the Early Upper Cretaceous . Arminisaurus was a basic representative of the group, but shows anatomical features (including the notch in the lower jaw and the lateral keel on the shoulder blade ) that were previously only known in a group of plesiosaurs, the Leptocleidia , that appeared 50 million years later .
The following cladogram from Sachs & Kear (2017) shows the relationship to other pliosaurs:
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literature
- ↑ a b c d e f S. Sachs, B. Kear: A rare new Pliensbachian plesiosaurian from the Amaltheenton Formation of Bielefeld in northwestern Germany . In: Alcheringa . 2017. doi : 10.1080 / 03115518.2017.1367419 .
- ^ Ancestor of sea reptile super predators found in Germany . University of Uppsala.
- ↑ S. Schubert: The Pliensbachium in the border area Lower / Upper Pliensbachium (Carixium / Domerium) of Pödinghausen in the Herford Lias hollow . In: Reports of the natural science association for Bielefeld and the surrounding area . 44, 2004, pp. 7-39.
- ↑ S. Schubert: The Ober-Pliensbachium (Domerium) of the Herford Lias basin — Part 1 — The outcrops . In: Geology and Paleontology in Westphalia . 68, 2007, pp. 1-90.