A rare and unusual trace fossil from the Lower Jurassic (Lias Group) of Ketton, East Midlands, UK

The top of the Whitby Mudstone Formation (Lias Group, Toarcian, Bifrons ammonite Zone) is exposed low in the geological Site of Special Scientific Interest at Ketton Quarry, East Midlands. A rare burrow of Fustiglyphus annulatus Vialov from this part of the succession, not reported from the Whitby Mudstone Formation hitherto, was collected from float. In the dull brown mudrock, the burrow has a contrasting fill of grey sandstone. The shaft of the burrow is cylindrical, with two broad, bell-shaped chambers. Fustiglyphus annulatus is found in deeper water deposits in the post-Palaeozoic, so its occurrence in the Whitby Mudstone Formation, an offshore shelf deposit, is not unexpected. However, orientation is equivocal; the burrow was either angled at 45 degrees to bedding, based on the evidence of an associated Arenicolites isp., or parallel to bedding, its common configuration.