THE LATE CAMBRIAN (MARJUMAN) TRILOBITE GENUSHYSTEROPLEURARAYMOND FROM THE COW HEAD GROUP, WESTERN NEWFOUNDLAND

Abstract

Although known previously from only two specimens from northern Greenland, new material from Marjuman boulders in debris flows of the Cow Head Group of western Newfoundland demonstrate that Verditerrina Robison is a menomoniid trilobite that is closely related to Hysteropleura Raymond. Following a parsimony analysis using the PAUP program, Verditerrina is used at the subgeneric level to label a distinctive monophyletic group within Hysteropleura. Three new species are established for the Newfoundland material: Hysteropleura (Verditerrina) adraini, H. (V.) edgecombei and H. (V.) ramskoldi. All three species undergo substantial modification of the anterior border of the cranidium during holaspid ontogeny. Two of the species, H. (V.) adraini and H. (V.) edgecombei, develop elongate, tongue-like borders that are reminiscent of those of calymenids such as Spathocalymene Tillman.