A rectal foreign body in a 65 million year-old Danish sea urchin

Since David B. Busch and James R. Starling, won the 1995 Ig Nobel Literature prize for their deeply penetrating 1986 research report, “Rectal foreign bodies: Case Reports and a Comprehensive Review of the World’s Literature” the body of literature on the subject and the number of cases has increased considerably. By 2012, no less than 589 reports on these inconveniences have been published. All cases, however, refer to humans. But now a paper has come to our attention that details the first documented case of a rectal foreign body in a 65 million year-old sea urchin from Denmark.

Close up anus sea urchinJesper Milan, Bo W. Rasmussen and Lothar H. Vallon of Geomuseum Faxe and Natural History Museum of Denmark report ‘An unusual taphocoenosis of a sea urchin and a rectally inserted turriform gastropod from the lowermost Paleocene of Stevns Klint, Denmark’ in New Mexico Museum of Natural History and Science Bulletin 67 (2015): 231-234:

A specimen of the common irregular echinoid Echinocorys sulcata (Goldfuss, 1826), recovered from the lowermost Paleocene Stevns Klint Formation, at Stevns Klint, Denmark, is of note in revealing a perfect external mold of the turriform gastropod Cerithiella fenestrata (Ravn, 1902) in the anal opening. The gastropod penetrated over a length of 21 mm perpendicularly into the echinoid test, and impressions in the surrounding matrix show the gastropod to have protruded over a length of 8 mm out of the test, being tightly lodged in the periproctal opening. It is assumed that this unusual combination resulted from the activities of bioturbators which, by chance, pushed the empty gastropod shell into the anal opening of the test of the dead echinoid, although other, more colorful, explanations cannot be excluded.

When asked about the significance of this discovery, Jesper Milàn answered by e-mail:

… it might be of some comfort for the unfortunate people who had to take the long walk to the doctor, to know it has happened to sea urchins long before any humans were present on the planet.

The images below illustrate the remarkable fossil association, where A is the sea urchin, B close-up of the anal opening showing the imprint of the gastropod shell, C silicone cast of the imprint, and E transparent CT-image of the sea urchin showing the orientation of the shell.

Milàn et al - Echinoid with snail - Fig 3 color

BONUS: Jesper Milàn (co)authored two recent papers that detail the discovery of vertebrate coprolites (fossil droppings) near the Danish shell-in-sea-urchin and elsewhere in Europe.