Article: Pedicellariae of two Silurian echinoids from western England
Pedicellariae have been discovered on the Silurian (Ludlovian) echinoids Echinocystites pomum and Palaeodiscus ferox from Leintwardine, England. All pedicellariae of both species are tridentate in form and simple in morphology. Most are interambulacral in position. Pedicellariae of E. pomum are abundant, all are probably three-valved, and of variable size. Those of P. ferox are relatively rare, apparently two-valved, and small in size. These pedicellariae, and an Australian occurrence, are the oldest known echinoid pedicellariae. The unusually large size of one fossil pedicellaria, combined with a general morphology of all pedicellariae intermediate between that of spines and modern pedicellariae suggests that pedicellariae were derived from spines.