HEAD SEGMENTATION IN EARLY CAMBRIAN FUXIANHUIA - IMPLICATIONS FOR ARTHROPOD EVOLUTION

The arthropod Fuxianhuia from the Chengjiang fauna displays primitive aspects of cephalic segmentation and trunk limb morphology that indica te a basal position within Euarthropoda. The cephalon consists of an e ye-bearing sclerite that articulates with a head shield bearing antenn ules and subchelate appendages. Eye stalks, antennules, and subchelate appendages are proto-, deuto-, and tritocerebral limbs and organs, re spectively. The anterior position of the eye-bearing sclerite parallel s the embryonic origin of arthropod eye lobes. The head of Fuxianhuia includes the acron and one somite and is regarded as a protocephalon. The definitive head of arthropods may have fused separate eye-bearing and appendage-bearing sclerites.