Cyclaster danicus, a shallow burrowing non-marsupiate echinoid

The spatangoid Cyclaster danicus has been placed in the genus Brissopneustes by previous authors. The material from the Lower Danian of Denmark includes some abnormal individuals with depressed apical area. These have been previously interpreted as females with a marsupium. A study of both normal and abnormal tests indicates that the depressed apical area is not a marsupium but rather a malformation, possibly caused by adverse environmental conditions or by a parasite. The skeletal morphology indicates that C. danicus was a shallow burrowing form but the malformed individuals probably did not burrow.