|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||Age range and collections|
If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
|J. Sprinkle 1973||Calyx flattened, elliptical to elongate heart-shaped with a flattened summit; made up of depressed top and bottom central areas with few, very large, thin, central plates, and surrounded by a raised and thickened rim with 8-12 U-shaped marginal plates extending part way into the central areas. Summit (oral surface) constricted and slanted, composed of marginals and small accessory plates (oral?) bearing central mouth and 2 short lateral ambulacra leading to 16-20 brachioles about 1 1/2 times as long as the calyx. Brachioles normally plated (biserial alternate) over most of length, but at proximal end plating is modified to biserial opposite for first 5-10 brachiolar plates. Anal pyramid below summit at lateral edge of central area, surrounded by 3 marginals and 1 central. Stem reduced, consisting of 1 or 2(?) inflated globular or rounded-conical columnals attached to 2-3(?) basal marginals. Early middle Ordovician (Whiterockian), central Nevada.|