Marine coprolite with ring-shaped inclusions

Rings (fish vertebrae?)
Church Cliff Bay Lyme Regis, Dorset, England
United Kingdom
5.3 x 3.7 x 1.3 cm

This coprolite specimen has been cut in half and polished. As with many of the coprolites found in Church Cliff Bay, the exterior surface has been eroded by the surf. Fossil feces of this type are generally attributed to marine reptiles such as ichthyosaurs or plesiosaurs; however, it is nearly impossible to definitively identify their creator.

What is fascinating about this poo, is that its LOADED mysterious inclusions. The University of Minnesota's X-ray CT Lab was kind enough to provide imagery so that we could see inside this coprolite. Because of the size and density of this coprolite, it is hard to isolate individual inclusions. That said, in the last image, a faint cluster of ring-shaped objects can be seen.

William Buckland discussed inclusions such as these in his 1829 paper On the Discovery of Coprolites, or Fossil Faeces, in the Lias at Lyme Regis, and in other Formations. He thought these rings might be from the suckers of cephalopods, but admitted the vertebrae of some small fish found in the formation were about the same size and shape as the rings found in this type of coprolite.