Tooth structure and phylogeny of the Upper Permian echinoid Miocidaris keyserlingi

Abstract
SUMMARY: Miocidaris keyserlingi is found in the Upper Permian Ford Formation, Zechstein Cycle 1, of the Sunderland district. It is confined to reef core and fore-reef talus slope facies and is absent from higher energy reef-crest and reef-flat habitats. Well preserved material permits the description of stereom microstructure and tooth construction. M. keyserlingi has teeth identical in structure to those of Recent cidarids and this contrasts with tooth structure in both the Carboniferous archaeocidarids and the early Jurassic euechinoids. Hemipyramid morphology and perignathic girdle structure also demonstrate the close relationship between M. keyserlingi and Recent cidaroids. Euechinoids and cidaroids must have diverged prior to the Upper Permian and at least two separate lineages of echinoids passed across the Permo-Triassic boundary.