Cyathotheca suecica and its bearing on the evolution of the Edrioasteroidea

Publisher Website
Google Scholar
Abstract
The European Ordovician edrioasteroid Cyathotheca has a variable tubular theca composed of a single plate. The oral surface is covered by 5 large inter-radial deltoids fused to biserial ambulacral cover plates, and a periproct in the C-D inter-radius accompanied by 2 or 3 adanal plates. Cyathotheca lacks ambulacral flooring plates. The American and Baltic Ordovician genus Cyanthocystis is identical except that is has a complete ring of small peripheral plates surrounding the deltoids. Both genera are assigned to the family Cyathocystidae. The Devonian genera Timeischytes and Hadrochthus are regarded as neotenous offshoots from the Agelacrinitidae and unrelated to cyathocystids. True cyathocystids arose neotenously from the Cambrian stromatocystitids by attachment of the centro-dorsal and failure to develop further aboral or ambulacral plates. This branch represents a separate evolutionary line to the main stromatocystitid-endrioasterid-isorophid line.

This publication has 3 references indexed in Scilit: