Obscure D.o.t.W: Ruehleia bedheimensis

After a long hiatus, here's the next entry in 'Obscure Dinosaur of the Week'!

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Name: Ruehleia bedheimensis
Etymology: In honour of the collector of the fossil, Hugo Ruhle von Lilienstern of Bedheim, South Thuringia.
Distribution: Late Triassic (Norian) of Thuringia, Germany.
Type Specimen: near complete composite skeleton lacking a skull.
Estimated size: ~6.5 m long
First described by: Galton, 2001a. Originally referred to Plateosaurus plieningeri HUENE, 1907-08 by Ruhle von Lilienstern et al. (1952).

Interesting fact: Do these fossils belong to many genera, or just one?

Normally, when a dinosaur is misidentified as the wrong genus or species, it is due to poorly preserved or very scrappy fossil remains confounding  the original identification. But in the case of Ruehleia bedheimensis, we have a nearly complete and well preserved fossil. So what went wrong?

It all comes down to identification and classification of specific bones.

Most animals with a backbone or spine (vertebral column) have sacral vertebrae: the part of the vertebral column that sits between the hips. Early dinosaurs had two sacral vertebrae, but some prosauropods had an extra sacral vertebrae, either being 'borrowed' from the tail end (caudosacrum - see below figure, bottom left) or from the head-end (dorsosacrum - see below figure, bottom right) of the vertebral column.

Top: Plateosaurus skeleton in right lateral view, with the sacral vertebral region marked by a red square, and two sacral vertebrae plus the caudosacral (mostly hidden behind the right ilium) coloured in red. Scale bar is 50 cm. Bottom: the two different ways some prosauropods had their sacral vertebrae configured; Bottom left: sacral vertebrae of P. longiceps in right lateral view, showing two sacral vertebrae (s1 and s2) plus a caudosacral (cs). Scale bar is 5 cm. Bottom right: sacral vertebrae of Jingshanosaurus in right lateral view, showing a dorsosacral (ds) plus two sacral vertebrae (s1 and s2). Scale bar is 5 cm. Figures taken from Galton et al. (2004).

Plateosaurus had two sacral plus one caudosacral vertebrae. But on closer inspection, some fossils assigned to Plateosaurus plieningeri were found to have two sacral plus one dorsosacral vertebrae (Galton, 2001b). By definition, these fossils with dorsosacral vertebrae could not belong to Plateosaurus, and instead had to belong to another prosauropod genus. And as there were some other different features in the hip and hand bones, it was decided that the fossil belonged to a completely new prosauropod genus, Ruehleia bedheimensis (Galton, 2001a).

So, not only can you find new dinosaur species or genera by going into the field and digging up new fossils, or by scouring museum collections for unlabelled or uncategorised specimens, you can also find them as well preserved fossils already assigned to a species and hiding in plain site!

Location of continents during the Late Triassic (Norian). The purple circle indicates the location of the modern day fossil. Image from the PBDB Navigator.

Simplified cladogram of all non-avian dinosaurs. R. bedheimensis was a plateosaurid plateosaur, within sauropodomorpha.

References
Galton, P. M., 2001a. Prosauropod dinosaurs from the Upper Triassic of Germany. In: Colectivo Arqueológico - Paleontológico De Salas (Eds.): Actas de las I Jornadas Internacionales Sobre Paleontología de dinosaurios y su entorno. Junta de Castilla y León, Salas de los Infantes (Burgos, España): 25-92.

Galton, P. M., 2001b. The prosauropod dinosaur Plateosaurus Meyer, 1837 (Saurischia: Sauropodomorpha; Upper Triassic). II. Notes on the referred species. Revue Paléobiologie, Genève 20(2): 435-50

Galton, P. M., Upchurch, P. 2004. Prosauropoda. In Weishampel, D. B., Dodson, P., and Osmolska, H. (eds.), The Dinosauria (second edition). University of California Press, Berkeley, pp 232-258

von Lilienstern, R., Lang, H. M., Huene, F. v., 1952. Die Saurier Thüringens. Fischer. Jena, 42 p.