|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||Slender, fusiform, probably about 60 mm long in contracted state; with principal ambulacrum and branch separated by two interambulacral areas; 12 interambulacral areas between branch and principal ambulacrum in next volution; ambulacrum complex, in cross-section with about 5 medial small plates and 3 to 4 laterally on each side; ambulacrum with lateral pores on each side for "tubefeet"; interambulacral areas built of short plates; at least every other medial interambulacral plate with a well developed spine, spinose plates usually slightly larger than non spinose plates; lateral interambulacral plates slightly more numerous than medial plates.|
|J. W. Durham 1993||As for genus [ Helicoplacida with tubefeet emerging between sequential ambulacral plates (see Durham, 1967, text-fig. I; Figure 3.3 herein), and 12 interambulacral areas involution adoral to primary ambulacrum.]|
|B. C. Wilbur 2006||As for genus. [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.]