Cotyledion tylodes is an extinct, stalked filter-feeder known from the Chengjianglagerstatten. The living animal reached a couple of centimetres in height, and bore a loose scleritome of ovoid sclerites. Its interpretation has been controversial, and it has been previously identified as a carpoidechinoderm,[1] or as a stem groupechinoderm.[2]C. tylodes is now classified as a stem groupentoprocta based on new fossils that clearly show a U-shaped gut and a crown of tentacles.[3]
This entoproct interpretation of Cotyledion, however, has been questioned by Mark McMenamin, who considers it best interpreted as a stem group echinoderm based on the morphology of its stem sclerites.[4]
^Clausen, S. B.; Hou, X. G.; Bergström, J.; Franzén, C. (2010). "The absence of echinoderms from the Lower Cambrian Chengjiang fauna of China: Palaeoecological and palaeogeographical implications". Palaeogeography, Palaeoclimatology, Palaeoecology. 294 (3–4): 133–141. Bibcode:2010PPP...294..133C. doi:10.1016/j.palaeo.2010.01.001.