Edrioasteroidea
Edrioasteroids Temporal range:
Possible Ediacaran occurrence | |
---|---|
Streptaster vorticellatus (13 mm across) from the Upper Ordovician of Kentucky, USA | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Echinodermata |
Subphylum: | Crinozoa |
Class: | †Edrioasteroidea Billings 1858 |
Genera | |
See text |
Edrioasteroidea is an extinct
The oldest undisputed fossils of Edrioasteroidea are known from
Anatomy
The body plan for this class was simple: a main body (theca), composed of many small plates, with 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 consisted of five arms, or ambulacra, in the body wall radiating outwards from the central mouth. 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 that roof the food groove. The anus was 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
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, which was about 12 millimetres (0.47 in) wide in the genus Giganticlavus, followed by the pedunculate zone attached to the peripheral rim of 12 millimetres (0.47 in).[5]
Taxonomy
List of genera
A very incomplete list of some genera.
- Walcottidiscus (oldest undisputed edrioasteroid, from the Middle Cambrian Burgess Shale community)
- W. typicalus
- Kailidiscus
- K. chinensis
- Edrioaster (type genus)
- E. bigsbyi
- E. priscus
- Edriophus
- E. levis
- Paredriophus
- P. elongatus
- Totiglobus
- T. nimius
- T. lloydi
- Lebedodiscus
- Foerstediscus
- F. grandi
- F. splendens
- Cystaster
- C. stellatus
- Cryptogoleus
- C. chapmani
- Bellochthus
- Streptaster
- S. vorticellatus
- Cryptogoleus
- C. chapmani
- Carneyella
- C. pilea
- C. faberi
- C. ulrichi
- Isorophus
- I. cincinnatiensis
- Isorophusella
- Camptostroma
- **C. roddyi
- Rectitriordo
- Agelacrinites
- Krama
- K. devonicum (Bassler), 1936
- Parakrama
- Hemicystites
- H. bohemica
- H. chapmani
- H. devonicus
- Neoisorophusella
- N. lanei
- N. berryi
- N. maslennikovi
- N. whitesidei
- Curvitriordo
- Thresherodiscus
- T. ramosa (Foerste, 1914)
- Postibulla
- P. westergaardi
- Parapostibulla
- P. belli
- P. graysoni
- Eopostibulla
- Pyrgopostibulla
- Yorkicystis
- Torquerisediscus
- Cooperidiscus
- Dynocystis
- Stalticodiscus
- Ulrichidiscus
- Clavidiscus
- Discocystis
- Hypsiclavus
- Spiraclavus
- Giganticlavus
- Lispidecodus
- L. plinthotus (Kesling, 1967)
References
External links
All accessed on March 8, 2008.
- http://www.ucmp.berkeley.edu/echinodermata/edrioasteroidea.html University of California, Berkeley.
- http://drydredgers.org/edrio1.htm Compiled by Colin D. Sumrall.
- https://web.archive.org/web/20060830083438/http://www.tulane.edu/~csumral/Abstract Spiraclavus nacoensis, a New Species of Clavate Agelacrinitid Edrioasteroid from Central Arizona by Colin D. Sumrall.
- http://www.science-art.com/image.asp?id=1357 Archived 2007-09-28 at the Wayback Machine Reconstruction by Emily Damstra.
- http://gsa.confex.com/gsa/2003AM/finalprogram/abstract_65113.htm Archived 2012-02-05 at the Wayback Machine Geological Society of America.
- https://web.archive.org/web/20060830083430/http://www.tulane.edu/~csumral/morph.html by Colin D. Sumrall
Taxonomy
Gallery
-
Foerstediscus splendens
-
The Upperbryozoan