Traces of Sublethal Injuries in Upper Cretaceous Echinoid Tests from the Vicinity of Volsk (Lower Volga Region)

Three species of echinoids Conulus matesovi Moskvin, Echinocorys ovata (Leske) and Micraster corbovis Forbes from Turonian and Campanian deposits of Lower Volga region, with traces of the sublethal injuries in the tests, are described. Such injuries are of particular interest as they are not related to commensalism, predation, parasitism, or other effects of different animals, but are the result of a mechanical collision of echinoid tests with empty shells of inoceramids, which resulted in a foreign object being embedded and remaining in the tests but did not lead to their destruction or the death of the organism. Formation conditions and taphonomic aspects of the occurrences are considered. Possible mechanisms of sublethal injuries are analyzed.