title: New reconstruction of the Wiwaxia scleritome, with data from Chengjiang juveniles.
abstract: Wiwaxiids are a problematic group of scale-covered lophotrochozoans known from Cambrian Stages 3-5. Their imbricating dorsal scleritome of leaf-like scales has prompted comparison with various annelids and molluscs, and has been used as a template to reconstruct the articulation pattern of isolated Small Shelly Fossils. The first articulated specimens of Wiwaxia from the Cambrian Stage 3 Chengjiang Konservat-Lagerstätte show that the Wiwaxia scleritome comprised nine equivalent transverse rows associated with outgrowths of soft tissue, but did not possess a separate zone of anterior sclerites. This serial construction is fundamentally incompatible with the circumferential disposition of sclerites in early molluscs, but does closely resemble the armature of certain annelids. A deep homology with the annelid scleritome must be reconciled with Wiwaxia's mollusc-like mouthparts and foot; together these point to a deep phylogenetic position, close to the common ancestor of annelids and molluscs.
authors.affiliation: Early Life Institute, State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, 710069, P. R. China.
authors.forename: Zhifei
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK.
authors.forename: Martin R
authors.initials: MR
authors.lastname: Smith
authors.affiliation: Early Life Institute, State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, 710069, P. R. China.
authors.forename: Degan
authors.initials: D
authors.lastname: Shu
mesh_terms: D000818:Animals; D000845:Annelida / Q000033:anatomy & histology; D005580:Fossils / Q000033:anatomy & histology*; D008974:Mollusca / Q000033:anatomy & histology; D010163:Paleontology