Cheloniellida
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The Cheloniellida Broili, 1932 are an unranked taxon (usually referred to as a class or order) of extinct Paleozoic arthropods, currently (Dunlop & Selden, 1997; Dunlop, 2002) thought to be a member of the Arachnomorpha and related to the Chelicerata and the Trilobita, while not included in any of those. There are six included genera, dating from Ordovician, Silurian and Devonian.
[edit] Included genera
- Cheloniellon Broili, 1932 - Lower Devonian, Germany
- Duslia Jahn, 1893 - Upper Ordovician, Czech Republic
- Neostrabops Caster & Macke, 1952 - Upper Ordovician, USA
- Paraduslia Dunlop, 2002 - Lower Devonian, Russia.
- Pseudarthron Selden & White, 1984 - Upper Silurian
- Triopus Barrande, 1872 - Upper Ordovician
[edit] Relationships - varied proposals
"Originally Cheloniellon was believed to be similar to trilobites (Broili 1932), though subsequent authors have suggested suggested that it is related to trilobites and Cambrian “merostomoids” (Størmer 1944), that it is a late representative of a trilobitomorph group giving rise to Chelicerata (Stürmer & Bergström 1978), that it is related to “loricate” crustaceans (Delle Cave & Simonetta 1991) or that it is the sister group to Chelicerata (Wills et al. 1995; Dunlop & Selden 1997)." [Account by Dunlop, 2002].
- Class Cheloniellida, sister group to class Crustacea (Boudreaux, 1979).
- Order Cheloniellida in subclass Petalopleura in class Artiopoda, this being sister to class Marellomorpha (Hou & Bergström, 1997).
- One of the five major taxa of the Arachnomorpha, sister group to the Chelicerata. The other three are Trilobita, Aglaspidida and Strabopida (Dunlop & Selden 1997, repeated by Budd, 1997).
[edit] References
- Boudreaux H. B. (1979). Arthropod phylogeny with special reference to insects. John Willey & sons, New York, Chichester, Brisbane, Toronto. 320 pp.
- Budd, Graham E. (1997). Stem Group Arthropods from the Lower Cambrian Sirius Passet Fauna of North Greenland. In Fortey, R.A.; Thomas R.H. (eds.): Arthropod Relationships. Systematics Association Special Volume Series 55.
- Jason A. Dunlop and Paul A. Selden. (1997).The early history and phylogeny of the chelicerates. Arthropod Relationships, pp. 237-245, R. A. Fortey & R. H. Thomas (eds.), Systematics Association Special Volume Series 55.
- Xianguang Hou & Bergström J. (1997). Arthropods of the Lower Cambrian Chengliang fauna, southwest China. Fossils & Strata, No.45: 1-116
