ATremadocian (EarlyOrdovician) palaeoscolecidan worm from graptolitic shales inHunanProvince,SouthChina

Abstract

AbstractA new locality exposingTremadocian (EarlyOrdovician) graptolitic shales inHunanProvince,SouthChina, has yielded an exceptionally well‐preserved annulated worm. This palaeoscolecidan is described asWaflascolex changdensisgen. et sp. nov. and reveals extremely fine detail of the cuticle organization and plating array. The new taxon is characterized by three critical characters: incomplete plate rows that occur only on the posterior end of the worm (except in the posterior‐most area) and do not extend over the entire circumference or along the entire trunk; a regular rhomboidal array of platelets around intercalations; and reduced cuticular organization at the posterior termination. The unique cuticular organization and platelet ornamentation in the new taxon offer insight into functional differentiation of plates in the scleritome. Palaeoscolecid distribution through the earlyPalaeozoic is reviewed, showing that the worms were widespread in theCambrian andOrdovician, but became more restricted during theSilurian. Ordovician palaeoscolecidans are diverse in scleritome architecture, and strikingly different fromCambrian taxa, indicating that this group diversified as part of theGreatOrdovicianBiodiversificationEvent.