Superregnum: Eukaryota
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Echinodermata
Subphylum: Eleutherozoa
Superclassis: Asterozoa
Classes: †Somasteroidea
Ordo: †Goniactinida
Familia incertae sedis: †Archegonasteridae – †Chinianasteridae
Name
Somasteroidea Spencer 1951
References
Spencer, W.K. 1951. Early Palaeozoic starfish. Philosophical Transactions of the Royal Society of London series B 235(B623): 87–129. Reference page.
Links
Somasteroidea data
The Somasteroidea, or Stomasteroidea, is an extinct order of asterozoan echinoderms first defined in 1951 by W. K. Spencer.[1] Their first appearance in the fossil record was in the Early Ordovician (Tremadocian) and they had become extinct by the Late Devonian (Famennian). They are similar to the asteroids in that their bodies are flattened dorsoventrally and they have five petaloid arms with broad bases. The ambulacral plates in somasteroids are simple and unspecialized, and the arms were thought to be not flexible and were unable to assist in feeding, but the oral mouth parts were more complex.[6] According to the World Register of Marine Species, Stelleroidea is no longer considered valid and it has since been absorbed into Somasteroidea and Asterozoa.[7]
References
W. K. Spencer. 1951. Early Palaeozoic starfish. Philosophical Transactions of the Royal Society of London, series B 235(B623):87-129
W. K. Spencer. 1927. A monograph of the British Palaeozoic Asterozoa. Monograph of the Palaeontographical Society, London 1925(7):325-388
D. B. Blake. 2000. An Archegonaster-like somasteroid (Echinodermata) from Pomeroy, co. Tyrone, Northern Ireland. Irish Journal of Earth Sciences 18:89-99
H. G. Owen. 1965. A monograph of the British Palaeozoic Asterozoa. Table of contents, supplement and index. Monograph of the Palaeontographical Society, London 1964:541-583
H. B. Fell. 1963. A new family and genus of Somasteroidea. Transactions of the Royal Society of New Zealand, Zoology 3(13):143-146
Somasteroidea Tree of Life Web Project. Retrieved 2011-09-29.
Asterozoa World Register of Marine Species. Retrieved 2011-09-29.
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