Kailidiscus, a new plesiomorphic edrioasteroid from the basal Middle Cambrian Kaili biota of Guizhou Province, China

Abstract

A new genus and species of edrioasteroid grade echinoderm, Kailidiscus chinensis, is described from the Kaili Biota of the basal lower Middle Cambrian Kaili Formation from Guizhou Province, China. This echinoderm has a strong resemblance to isorophid edrioasteroids, bearing a well-developed peripheral rim, long curved ambulacra, and slightly imbricate interambulacral plating at maturity. However, the presence of pore-bearing, double biserial floor plates, tiered cover plates, lack of radially positioned oral frame plates, and unincorporated hydropore/gonopore are unknown in isorophids. Many of these features bear strong resemblance to eocrinoids and helicoplacoids, attesting to the plesiomorphic nature of this taxon. Despite the obvious anatomical differences, specimens of this species preserve a complete ontogeny that resembles that of isorophids. Juveniles show a discoidal theca with straight ambulacra that transitions to an inflated theca with strongly curved ambulacra with maturity.