|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Helicoplacoidea - Helicoplacidae
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. W. Durham 1993||Paired grooves for tubefeet in opposing margins of contemporaneous ambulacral plates. Plates of medial column of interambulacra pustulose or with longitudinal ridges. In each volution eight interambulacral areas adoral to primary ambu- lacrum.|
|B. C. Wilbur 2006||Echinoderm with a spindle to bulb-shaped theca composed of left-handed spiraling interambulacral pleats composed of ridge and accessory plates, which allowed for expansion and contraction of the test. Three ambulacral branches are imbedded within interambulacral pleats and extend away from a mediolateral mouth; two separated by one to three interambulacral pleats extend toward the upper pole, and one toward the lower pole. Ambulacra are comprised of biserial floor-plates and sheets of coverplates. The ambulacral groove have sutural gaps between laterally adjacent floorplates, which form compensation space for the ampullae of tube feet.|