EOCRINOIDS OF THE MIDDLE CAMBRIAN KAILI BIOTA, TAIJIANG COUNTY, GUIZHOU, CHINA

The Uppermost Lower to Middle Cambrian Kaili Formation in Taijiang County, Guizhou Province in SW China is older than the Burgess Shale but contains a number of Burgess soft-bodied genera. The Kaili Formation is about 200 meters thick and consists of mostly deeper water (inner to outer shelf) calcareous mudstones and shales. The bioturbation index, except near the top of the formation is 1 or low 2. The Kaili Biota ss. is the earliest and a very important Middle Cambrian Burgess Shale-type biota that contains eleven phyla. Despite their low diversity, echinoderms are second to arthropods (52+ genera) in numbers of fossils within the biota and are represented by three exceptionally well preserved eocrinoid species and a Stromatocystites-like edrioasteroid. "Sinoeocrinus globus" is the most abundant eocrinonid. It has a globular theca, very short column, with a large disc-like mutiplated holdfast, and spiral brachioles. It is over ten times more abundant than S. lui. Sinoeocrinus lui in adult forms, has an elongated theca, a long irregularly plated column with a small multiplated holdfast, and straight brachioles. A complete ontogenetic growth sequence of this species can be observed. Early juveniles ((thecal height (TH) less than 5mm)) commonly are paired at the holdfast. By TH 5mm a 2-1-2 ambulacral pattern is present derived from a 2-2 pattern. Sutural pores appear at the edges of thecal plates at about TH 10mm. Brachioles are added juxtaposed to original brachiole seats at the end of the ambulacra to produce lateral bunches. Both "S. globus" and S. lui are equally able to attach to the essentially unbioturbated sea floor or to brachiopods, pieces of trilobites, or other fossil particles. The third eocrinoid is very rare and undescribed. It has a very long column, globular theca, and numerous straight brachioles.