A nearly complete adult internal mould with some test, beautifully preserved on both sided, showing 4 whorls. The last few sutures are visible and the body chamber occupies 3/5 whorl. Despite its small size the ribbing and crenulate venter are clearly visible. These are the last representataives of the Cardioceratidae. The sudden diminution in size is however not an expression of phylogenetic gerontism. The last brief enfeebled appearance before extinction, for these forms occur in enormous numbers over a considerable range of strata, from the upper Eudoxus Zone to the lower Autissiodorensis Zone, and over a large area, from Britain to the Urals. Most remarkable is the apparent disappearance of the dimorphis; it has become so inconspicuous as to have escaped detection. From Ringstead, Dorset.
Size: 11.5 mm
Size: 11.5 mm