Thursday, March 28, 2013

An early Triassic European placodont

Reconstruction of the juvenile placodont 
Palatodonta bleekeri. The teeth are 
striking compared to other placodonts. 
Artist Credit: Jaime Chirinos.

Note that the University of Zurich press release refers to placodont reptiles as "dinosaurs," they are not dinosaurs. They are usually considered to be sauropterygians, Triassic stem reptiles.

Dental plaster dinosaurs were among the first marine reptiles. With typical cracking teeth they fed on molluscs and crustaceans. When and where these highly specialized marine reptiles arose was, up to now unclear. Recently, in the Netherlands, a 246 million years old skull of a young dental plaster dinosaur was discovered. Paleontologists of the Universities of Zurich and Bonn have now, that this is one of the first of these dinosaurs, and he was born in Europe.

While about 50 million years ago the dinosaurs populated patch tooth shallow, coastal regions of the Tethys Sea. The most striking feature of Placodonten how these dinosaurs are also called, was their teeth: your upper jaw possessed the palate and on the jawbone ever a series of plate-shaped teeth, while the lower jaw had only one row of teeth - teeth, ideal to gnaw to shellfish and crustaceans.

The emergence of these dental plaster dinosaur was not until now been resolved conclusively. A new discovery of a 246 million years old sediment layer illuminates the origin and phylogenetic development of Placodonten. As the Swiss-German team led by Torsten Scheyer, paleontologist at the University of Zurich shows, it is the skull of from Winterswijk (NL) to the original form of all known dinosaur tooth patch. The young animal lived 246 million years ago. Be approximately two inches big skull is well preserved, and his features set it apart from the previously known Placodonten.

The previously known primitive Placodonten have the characteristic of the group Doppelbezahnung maxillary teeth and have spherical. The eponymous plate-like teeth occur only in the mature dental plaster dinosaurs. "This has Winterswijker instance, unlike anything previously acquaintances no disc-shaped or spherical crack teeth, but rather conical, pointed teeth," says Scheyer the findings, "so that when biting the sharp teeth of the lower jaw precisely into the space between the palate and upper jaw bone teeth attacked . "

That it is the new find actually a Placodonten, typical of the group is double row of teeth in the upper jaw. According to the researchers was the bit of Palatodonta bleekeri, the scientific name of Winterswijk instance that specializes in keeping soft prey firmly and penetrate. This Scheyer: "The Doppelbezahnung the discovery combined with his advanced age it can be concluded that it is a very original Placodonten have from then developed the later forms." From the formation of the crack teeth and the specialization on a diet shellfish and crustaceans occurred therefore within the evolution of dinosaur tooth patch.

The small Palatodonta bleekeri skull sheds new light on the debate about the origin area of ​​the paving dinosaur tooth: The recent discoveries could be both an emergence in the shelf sea areas of contemporary China and in Europe. Due to the advanced age of the Dutch discovery and its original form, now the European origin of the plaster dinosaur tooth is considered certain. Scheyer and colleagues hope to see more exciting discoveries from Winterswijk to drive the evolution of Placodonten further progress.

Citation
James M. Neenan, Nicole Klein, Torsten M. Scheyer. European origin of placodont marine reptiles and the evolution of crushing dentition in Placodontia. Nature Communications, 2013; 4: 1621 DOI: 10.1038/ncomms2633

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