title: Cambrian lobopodians and extant onychophorans provide new insights into early cephalization in Panarthropoda.
abstract: Cambrian lobopodians are important for understanding the evolution of arthropods, but despite their soft-bodied preservation, the organization of the cephalic region remains obscure. Here we describe new material of the early Cambrian lobopodian Onychodictyon ferox from southern China, which reveals hitherto unknown head structures. These include a proboscis with a terminal mouth, an anterior arcuate sclerite, a pair of ocellus-like eyes and branched, antenniform appendages associated with this ocular segment. These findings, combined with a comparison with other lobopodians, suggest that the head of the last common ancestor of fossil lobopodians and extant panarthropods comprized a single ocular segment with a proboscis and terminal mouth. The lack of specialized mouthparts in O. ferox and the involvement of non-homologous mouthparts in onychophorans, tardigrades and arthropods argue against a common origin of definitive mouth openings among panarthropods, whereas the embryonic stomodaeum might well be homologous at least in Onychophora and Arthropoda.
authors.affiliation: Early Life Evolution Laboratory, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China. ouqiang@cugb.edu.cn
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ou
authors.forename: Degan
authors.initials: D
authors.lastname: Shu
authors.forename: Georg
authors.initials: G
authors.lastname: Mayer
mesh_terms: D000818:Animals; D001181:Arthropods / Q000033:anatomy & histology*; D005075:Biological Evolution; D002681:China; D005121:Extremities / Q000033:anatomy & histology; D005580:Fossils; D006257:Head / Q000033:anatomy & histology; D009055:Mouth / Q000033:anatomy & histology