EXCEPTIONAL ACCUMULATIONS OF STATOLITHS IN ASSOCIATION WITH THE CHRISTIAN MALFORD LAGERSTATTE (CALLOVIAN, JURASSIC) IN WILTSHIRE, UNITED KINGDOM

摘要

In the shell-rich, laminated clays of the Phaeinum Subzone (Athleta Zone, upper Callovian, Middle Jurassic) of the Peterborough Member of the Oxford Clay Formation, large numbers of statoliths and otoliths have been recovered. This apparent mass mortality is associated with the Christian Malford Lagerstatte in which there is exceptional, soft-bodied preservation of coleoid fossils. Statoliths are the aragonitic 'stones' that are found in the fluid-filled cavities (or statocysts) within the cartilaginous head of all modern and probably many fossil coleoids. Jurassic statoliths are largely undescribed and there are no known genera or species available to aid their classification. Otoliths, which may be of somewhat similar appearance, are the aragonitic stato-acoustic organs of bony (teleost) fish. These are more familiar to micropaleontologists and have a better known, though limited, fossil record. The abundance of statoliths in the Phaeinum Subzone at Christian Malford may indicate a mass mortality of squid that extends over some 3 m of strata and, therefore, a considerable interval of time. This has been tentatively interpreted as a record of a breeding area (and subsequent death) of squid-like cephalopods over an extended period of time rather than a small number of catastrophic events.