Stenopelix

The holotype of Stenopelix from the Obernkirchener sandstone

  • Germany

Stenopelix (translated " narrow pelvis " ) is a known only by sparse finds genus of bird Beck dinosaurs ( Ornithischia ), possibly from the group of Pachycephalosauria or Ceratopsia. Only known species is S. valdensis ( the surname refers to the formation, the Wealden ).

From Stenopelix so far was only one copy, and found that only parts of the body skeleton. The skull, which would undoubtedly enable a precise systematization is not known.

Stenopelix was relatively small at around 1.5 to 2 m in length. In the only specimen found - this was from a nearly fully grown animal - the preserved part of the spine is 97 cm long and 55 cm, the tail was missing, the neck. He ran biped on its hind legs. It is often reconstructed based on Psittacosaurier or Pachycephalosaurier.

The fossil remains of Stenopelix were found in 1855 in the upper churches in Lower Saxony, known by its construction sandstone. The references were the sandstone quarries of Harrl, a western foothills of the Bückeberge, had been found in the recently already crocodile fossils ( and tortoise shells ) and later dinosaur tracks.

1857 was first described Stenopelix from Frankfurt paleontologist Hermann von Meyer ( 1801-1869 ). Its fossils is (late Berriasian ) dated to the Early Cretaceous an age 142-139 million years. At that time there were swamps of a large river deltas in the northerly Lower Cretaceous sea, which also left carbon deposits.

System

The systematic classification of Stenopelix is controversial since its first description.

By Franz Baron von Nopcsa he was discovered in 1917 in a separate family ( Stenopelyxidae ) classified and assigned 1923 Hypsilophodontidae ( Gazelle dinosaurs ). Alfred Romer arranged them in 1946 in the vicinity of a Psittacosaurier.

In a re-examination of the skeleton by Hermann Schmidt ( Münster) in the 1960s Stenopelix could be unambiguously assigned to the Ornithischia, due to the discovery of Postpubis extension of the pubic bone, a typical feature of the Ornithischia.

In the 1970s, Teresa Maryanska and Halszka Osmolska noted similarities of Stenopelix skeleton with by Polish expeditions in Mongolia newfound Pachycephalosauriern (Dick head skull dinosaurs). Examples of the similarities were according to these authors: in the construction of the pool the pubis ( pubic ) had no part in the acetabular cup ( acetabulum ) ( but this was refuted by Sues and Galton ) and the strong caudal fins ( the Sues and Galton then as sacral ribs identified ).

However, the Pachycephalosaurier are the Isle of Wight, known only from the Upper Cretaceous of East Asia and North America until Yaverlandia from the Lower Cretaceous ( about 125 million years). Peter Galton ( the describer of Yaverlandia ) arranged in 1976 and therefore Yaverlandia Stenopelix in the same genus a.

After a re-examination of fossils with Hans -Dieter Sues 1982 both saw in Stenopelix contrast, one of the previously oldest known ancestors of the ceratopsians. Because of its size, it is comparable to the Psittacosauriern among these the most. In contrast to the Psittacosauridae ( and Protoceratopsidae ) of the thigh (femur) of Stenopelix was longer than the shin (tibia), the basin was comparable: short extension on Präpubis, rear extension on the pubis short, lack of processus obturator (which otherwise as an key feature of the Ornithischia applies ). Maybe he can be classified also in the proximity of common ancestors of Pachycephalosaurier and ceratopsians, both of which are today considered to be related and grouped into the Marginocephalia.

Other scientists such as Robert Sullivan keep the finds for too sparse for a systematic mapping and lead him as " incertae sedis Ornithischia ".

The specimen was in the collection of Max Ballerstedt (1857-1945), the doyen of the dinosaur - track research in the Bückebergen, in high school Adolfinum Biickeburg and came in the 1970s at the Geological- Palaeontological Institute, University of Göttingen, where in 2008 geological Museum has also set up a replica.

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