SilesianTriassic

Reptilia indet.

Dating uncertain – Upper Roeth or Lower Muschelkalk (Olenekian or Anisian)

Upper Silesia, Poland

The specimen is the lateral gastralium (ventral rib) of an indeterminate reptile. Gastralia were present in almost all Triassic marine reptiles (the exception being Ichthyosauria). Their morphology is very similar, making such specimens non-diagnostic.

The specimen is approximately 56 mm long and 2 mm at its widest point. Its straight shape indicates that it is a lateral gastralium. Due to the length and lack of pachyostotic features, it seems that we can exclude the group Pachypleurosauridae. At this length, the animal must have been quite large.

The gastralia are dermal bones and were not connected to the axial skeleton, therefore they lack a proximal head – they have sharp, tapering tips. The gastralia formed a sort of basket protecting the abdomen.

The gastralia of Triassic reptiles are most often associated with V-shaped bones. Gastralia of this shape are called medial gastralia – they were located along the axis of symmetry of the animal while the lateral gastralia were located on the sides.

Reference:

Diedrich, C. G. (2013). Marine Triassic reptile biodiversity and change in the Bad Sulza Formation (Illyrian, Middle Triassic) of Central Germany and a contribution to the evolution of Nothosaurus in the Germanic Basin. New Mexico Museum of Natural History and Science Bulletin, 61, 147-157.