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Helicoplacidae
Taxonomy
Helicoplacidae was named by Durham and Caster (1966).
It was assigned to Helicoplacida by Durham (1993); and to Helicoplacoidea by Wilbur (2006).
It was assigned to Helicoplacida by Durham (1993); and to Helicoplacoidea by Wilbur (2006).
Synonymy list
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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.
Fm. †Helicoplacidae Durham and Caster 1966
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G. †Helicoplacus Durham and Caster 1963
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†Helicoplacus gilberti Durham and Caster 1963
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Invalid names: Helicoplacus casteri Durham 1993 [synonym], Helicoplacus curtisi Durham and Caster 1963 [synonym], Helicoplacus everndeni Durham 1967 [synonym], Helicoplacus guthi Durham 1993 [synonym], Westgardella blancoensis Durham 1993 [synonym], Westgardella firbyi Durham 1967 [synonym]
Invalid names: Westgardella Durham 1993 [synonym]
Diagnosis
Reference | Diagnosis | |
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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. |