THE STATUS OF BOTHRIOCIDARIS – RECONSIDERED

Since its original description in 1848, the taxonomic position of the Ordovician echinoderm Bothriocidaris has been the subject of dispute. In the 1920s and 30s, an intense, yet studiously polite, battle raged between the most pre-eminent echinologists of the day, with one camp seeing in Bothriocidaris the first echinoid from which all others are descended, and the other believing that Bothriocidaris is not an echinoid at all, but rather a member of the diploporite cystoids. More recently, bothriocidaroids have been considered as a short-lived aberrant echinoid order or as stem holothuroids.

The discovery of a bothriocidaroid from the Silurian of Anticosti Island, Canada, together with a cladistic analysis of bothriocidaroids plus other unequivocal Palaeozoic echinoids, suggests that Bothriocidaris is indeed an echinoid. Furthermore, rather than representing an unsuccessful offshoot from the main echinoid stock, this analysis suggests that the bothriocidaroids are most closely related to the palaechinids which proliferated during the Carboniferous. With Bothriocidaris no longer considered as a primitive echinoid, the origins of the echinoids must be sought in even earlier deposits.