Omphalosaurus was a marine reptile and probably an ancestor of the ichthyosaurs. It lived during Middle Triassic times, about 240 million years ago and consequently almost 10 million years before the first dinosaurs. There is very little known about the evolution of Omphalosaurus. Fossils of these reptiles have been found in Nevada, Spain, Austria and Spitzbergen until recently, consequently each single bone is important for reconstructing its evolutionary history. The Bremen collection owns a jawbone from the Schaumkalk (foam limestone) from Rüdersdorf, east of Berlin. This is the first fossil described of that species. Probably the animal looked like a modern dolphin, however, in contrast its body length did not exceed 150 cm. The fossil shows circular bottom-like teeth that enabled the reptile to crack even hard shells of bivalves and brachiopods that probably provided its diet. This perfectly fits to the supposed environment the animal inhabited. The rock releasing the Bremen reptile was investigated in detail. As a result the petrified sea floor deposit was believed to have been deposited in the proximate coastal seam of the ancient sea.
Habitat and distribution of Omphalosaurus
The Geosciences Collection posses the holotype of Omphalosaurus peyeri, a species recently described by Maisch & Lehmann (2002). This species is distinguished from other species of Omphalosaurus by possessing only one functional row of teeth. This makes it likely that it represents the basal most of all species of Omphalosaurus known so far.
The specimen was donated in 1903 by the Naturwissenschaftlicher Verein, but was not cataloged before 1913 in the collection of the former museum for Natural Sciences, Ethnology and Trading of the city of Bremen. Until 2001 this fossils was missidentified as the jaw fragment of the placodont reptile genus Placodus. A determination as a placodont was not astonishing since the teeth look superficially very similar. However, the teeth of Omphalosaurus show an orange-peel structure contrary to that of Placodus.
The Schaumkalk of Rüdersdorf (Streichan 1990) is interpreted as a deposit of the direct coastal area that was even run dry temporarily (Zwenger 1985). It fits well with the idea of a very shallow epicontinental sea, the North German Syncline, established in the early Middle Triassic. The Bremen specimen of Omphalosaurus lived consequently in the proximate coastal seam. The patchy distribution of Omphalosaurus in Northern Germany, Nevada, Spain, Austria and Spitzbergen is striking. At least in Northern Germany a further omphalosaurid reptile, Tholodus, lived simultaneously with Omphalosaurus. Nevertheless, fossils of Tholodus are alsovery rare.
- Maisch, M. W. & J. Lehmann (2002): A new basal omphalosaurid from the Middle Triassic of Germany. – Neues Jahrbuch für Geologie und Paläontologie, Monatshefte 2002(9): 513-525.
- Streichan, H.-J. (1990): Der Rüdersdorfer Muschelkalk. – In: Weidert, W.-K. (Hrsg.): Klassische Fundstellen der Paläontologie – Band II Korb, Goldschneck-Verlag, 66-77.
- Zwenger, W. H. (1985): Mikrofaziesuntersuchungen im Unteren Muschelkalk von Rüdersdorf. – Wissenschaftliche Zeitschrift der Ernst-Moritz-Arndt-Universität Greifswald, Mathematisch-Naturwissenschaftliche Reihe 34(4): 17-20.