Article: Appendages of the arthropod Aglaspis spinifer (Upper Cambrian, Wisconsin) and their significance

A single specimen of Aglaspis spinifer is unique in having the appendages preserved approximately in place. Re-examination has shown that the cephalic region bore four (perhaps five) pairs of appendages, and not six as Raasch (1939) claimed. The first pair was uniramous, apparently cylindrical and jointed, but cannot be confirmed as being chelate. The remaining pairs on the cephalic region were like those on the anterior half of the trunk, uniramous walking legs composed of five podomeres. The aglaspidids are therefore not chelicerates, and we do not consider them to be closely related to trilobites. The order is not assigned to any higher taxon. The record of Chelicerata in the Cambrian is dramatically reduced.