TRILOBITE APPENDAGE STRUCTURE - EOREDLICHIA RECONSIDERED

New interpretations are available from recently published appendages o f Eoredlichia intermedia (Early Cambrian Chengjiang fauna), the most p rimitive trilobite for which appendages are known. The basis (formerly identified as the coxa) is preserved in one appendage. An allegedly l ong proximal podomere in the endopod is actually subdivided into two a nd, at least in posterior appendages, each of these podomeres bears a strong, angular endite. The large, subquadrate basis, angular endite o n the first podomere of the endopod, and attachment of the exopod alon g the whole length of the basis are features shared with naraoiids, fo r which Naraoia longicaudata Zhang & Hou is exemplar. The long line of attachment of the exopod to the basis works as a hinge joint in E. in termedia and is a feature shared by Olenoides serratus. This joint all ows rotation of the basis and endopod around the hinge line, permittin g extensive leg movement without forcing the large exopod fan out of p osition. The shape of the basis in O. serratus is reinterpreted here, and a new reconstruction of the exopod shows detailed similarity to E. intermedia. The limbs of Eoredlichia show that appendage structure in primitive trilobites is little altered from shared ancestry with nara oiids.