Deuterostomia Homalozoa


Deuterostomia ├─Vetulicolia └─┬─Chordata └─Ambulacraria ├─Hemichordata └─┬─Vetulocystidae └─Homalozoa ├─Stylophora └─┬─Soluta └─┬─Cincta └─┬─Ctenocystoidea └─┬─Helicoplacoidea └─Echinodermata
   A Passing Grade 
   "Haplozoa" -- A Couple of Loose Ends

Rhenocystis latipedunculata

Rhenocystis latipedunculata a Mitratan carpoid from the Early Devonian (Seigenian/Emsian) Hunsruck Slate /lagerstatten, Bundenbach Germany; Length about 3 cm, with a 2.5 cm "tail"

Image copyright The Virtual Fossil Museum

Even for a phylum as unusual as the echinoderms, the carpoids, or homalozoa as they are also known, are strange. These small (mostly only about an inch in length, although a few grew a bit larger) armoured paleozoic animals lacked the usual radial symmetry of their echinoderm cousins, which means they had a definite "front" and "rear". Even so, they resemble no animals we are familar with; their irregular flattened, asymmetric body and long "arms" and "tail" make them look more like creatures from the pages of a science fiction novel.

Homalozoans have variously been interpreted as stem-group echinoderms, stem group chordates (the calcichordates hypothesis of Jefferies), and a assemblage of groups related to Crinoids and Blastozoa. MAK120113

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