Edrioasteroidea (Edrioasteroids)

The Edrioasteroids are an extinct class of echinoderm that lived from the Ediacaran (if Arkarua was indeed an edrioaster) to the Permian periods of geologic time, about 300 million years ago. The animals usually consisted of a disk-like upper body made of many plates. The body plan for this class was simple: a main body (theca), composed of many small plates, a peripheral rim for attachment, and (in some species) a pedunculate zone for extension and retraction. Circling and sometimes attached to the body was a peripheral rim of plates. The main feature was the presence of five arms, or ambulacra, contained in the body wall radiating from the central mouth outwards. The ambulacra grew either curved or straight. When curved, they may all turn in the same direction or else one or two on the right side will curve opposite the others. The ambulacra are built of underlying floor plates that form the food groove and protective cover plates the roof the food groove. The anus was situated under the mouth region and was made of small triangular plates to form a cone-shaped area. The bottom surface of the theca is unplated. Edrioasteroid species are distinguished by differences in the ambulacral curvature, the relationships of the cover plates, and ornamentation. The mode of life was sessile; they were often attached via a stalk made of small plates to a hard object such as a carbonate hardground or shell. Several examples of epibiotic attachment have also been noted. In the discocystinids, the area between the body and peripheral rim could be extended and retracted; in so doing the two were separated. The peripheral rim became the base of the stalk which was attached to a surface. Underneath the body was a recumbent zone about 12 millimetres wide in the genus Giganticlavus, followed by the pedunculate zone attached to the peripheral rim of 12 millimetres.

Source:
http://en.wikipedia.org/wiki/Edrioasteroidea

Stromatocystites pentangularis		p3380
Stromatocystites pentangularis		p3393
Stromatocystites pentangularis		VK395
Stromatocystites pentangularis		p3379
Stromatocystites pentangularis	Pompeckj (1895), Pl. XIII, fig. 1 a, b, c; Fatka et al. (2018), fig. 4A	XB5
Stromatocystites pentangularis		VK405
Stromatocystites pentangularis		p1606
Stromatocystites pentangularis		XB600
Stromatocystites pentangularis		XB594
Stromatocystites pentangularis		CW95
Stromatocystites pentangularis		OZ98
Stromatocystites pentangularis		CW48
Stromatocystites pentangularis		VK431
Stromatocystites pentangularis		VK432
Stromatocystites pentangularis		VK433
Stromatocystites pentangularis		CW64
Stromatocystites pentangularis		CW96
Stromatocystites pentangularis		CW49
Stromatocystites pentangularis		CW53
Stromatocystites pentangularis		CW58

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Img. 86:

Virtual museum of the Czech Geological Survey, www.geology.cz, (C) Czech Geological Survey, 2011, v.0.99 [13.12.2011]