Arachnomorpha ("Spider Form") Lameere 1890 is a subdivision of Arthropoda, containing the monophyletic group formed by the trilobites and other trilobite-like families (Helmetiidae, Xandarellidae, Naraoiidae, Liwiidae, and Tegopeltidae, and a diverse sister clade including the chelicerates. Great debate is held on the position of the Pycnogonida, which are currently thought not to be placed in the immediate vicinity of the Chelicerata (Dunlop & Arango, 2005).
There is no consensus as to assigning Arachnomorpha a formal Linnean category. It could be a Subphylum or a Superclass and then its subgroups Cheliceromorphora and Trilobita would be ranked as various infrataxa and the Chelicerata sensu stricto would be a Class.
The proposal of Lauterbach (1980) to consider the Olenellinae as sister group to the Chelicerata was refuted by Fortey & Whittington (1989), which contraposed many synapomorphies uniting them to the Trilobita instead.
Synonyms include Arachnata Paulus, 1979 and Palaeopoda Packard 1903.
Classification of the Arachnomorpha
-
- ???Pycnogonida Latreille, 1806 (incl. Pantopoda Gerstaecker 1863)
Arachnomorpha Lameere 1890 [= Arachnata Paulus, 1979, = Palaeopoda Packard 1903]
References
Cotton, T.J., and S.J. Braddy. 2004. The phylogeny of arachnomorph arthropods and the origins of the Chelicerata. Transactions of the Royal Society of Edinburgh: Earth Sciences, 94: 169–193,
Dunlop, J. A. & Arango, C. P. 2005. Pycnogonid affinities: a review. Journal of Zoological Systematics and Evolutionary Research, 43: 8-21.
Fortey, RA, and HB Whittington. 1989. The Trilobita as a natural group. Historical Biology, 2:125–138.
Lauterbach, K. E. 1980. Schüsselereignisse in der Evolution des Grundplans der Arachnata (Arthropoda). Abhandlungen des Naturwissenschaftlichen Vereins Hamburg (NF), 23:163-327.
|
