The first solute which is attached as an adult: A Mid-Cambrian fossil from Utah with echinoderm and chordate affinities

Abstract

A monotypic new genus, Coleicarpus, is proposed for Castericystis? sprinklei Ubaghs & Robison 1988, the only solute known to be attached when adult. Coleicarpus sprinklei was fixed by the tip of its stele or tail to trilobite exoskeletal fragments which themselves adhered to the sea bed. The tail of C. sprinklei is uniformly circular in cross-section and made of small non-imbricating plates which form imprecise transverse rings and longitudinal rows. The tail of C. sprinklei is not divided into discrete regions as are the tails of other solutes. C. sprinklei is probably the most primitive known solute because of its attachment and lack of tail regions. These features of its tail are consistent with the theory of the descent of solutes from a Cephalodiscus-like ancestor and also the phylogenetic placement of C. sprinklei in the stem group of the Dexiothetica, the monophyletic group which comprises the echinoderms and chordates exclusively. © 1996 The Linnean Society of London.