Nektaspida

Nektaspida Temporal range: Cambrian–Silurian PreЄ Є O S D C P T J K Pg N
Naraoia spinosa
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Stem-group:	Chelicerata
Order:	Nektaspida Raymond, 1920
Families
Liwiidae† Naraoiidae†

The Nectaspida (also called Naraoiida, Nectaspia and Nektaspida) is an extinct order of soft-bodied arthropods proposed by Raymond in 1920; its taxonomic status is uncertain. Specimens are known from the early Cambrian to the upper Silurian periods. Whittington (1985) placed the order in the Trilobita. Cotton & Braddy (2000) place it in a new "Trilobite clade" containing the Trilobita, recognizing the close affinities of the Nectaspids to trilobites. However this necessitates the inclusion of genera that look very little like trilobites.^[1] Strictly speaking, it is best placed in the stem-group to the chelicerates.^[2]

Naming history

The order was originally proposed by Raymond in 1920 as Nectaspia. Størmer corrected it to Nectaspida for the 1959 Treatise on Invertebrate Paleontology to conform with the names of the other trilobite orders. Whittington described it in 1985 with the spelling Nektaspida; the revised 1997 Treatise by Raymond and Fortey uses this spelling, as do other modern works.^[1]

References

1. ^ ^{a b} Budd, G. E. (1999). "A nektaspid arthropod from the Early Cambrian Sirius Passet fauna, with a description of retrodeformation based on functional morphology". Palaeontology 42: 99. doi:10.1111/1475-4983.00064.  edit
2. ^ Budd, G. E.; Jensen, S. (2000). "A critical reappraisal of the fossil record of the bilaterian phyla". Biological Reviews of the Cambridge Philosophical Society 75 (2): 253–95. doi:10.1017/S000632310000548X. PMID 10881389. 

External links

• Are Naraoids trilobites? -- photographs of specimens and discussion of classification controversy.
• Order Nectaspida -- more technical overview with references and descriptions of known genera.