|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 1967||
Comparatively slender, fusiform helicoplacoids with short, mostly highly spinose medial interambulacral plates; ambulacra complex, medial plates slender and very numerous.
|J. W. Durham 1993||Helicoplacida with tubefeet emerging between sequential ambulacral plates (see Durham, 1967, text-fig. I; Fig- ure 3.3 herein), and 12 interambulacral areas involution adoral to primary ambulacrum.|
|B. C. Wilbur 2006||Helicoplacoids with a rhombus-shaped plate at the intersection of the distal corners of floorplates and proximal corners of primary coverplates. Faces of interambulacral plates are pentagons with the acute end directed away from the animal.|