The group was initially contested by a significant minority of biologists. Some argued for groupings based on more traditional taxonomic techniques,[9] while others contested the interpretation of the molecular data.[10][11]
^Eernisse, D.J.; Albert, J.S.; Anderson, F.E. (1992). "Annelida and Arthropoda are not sister taxa: A phylogenetic analysis of spiralian metazoan morphology". Systematic Biology. 41 (3): 305–330. doi:10.1093/sysbio/41.3.305.
^Aguinaldo, A.M.A.; Turbeville, J.M.; Linford, L.S.; Rivera, M.C.; Garey, J.R.; Raff, R.A.; Lake, J.A. (29 May 1997). "Evidence for a clade of nematodes, arthropods, and other moulting animals". Nature. 387 (6632): 489–493. Bibcode:1997Natur.387R.489A. doi:10.1038/387489a0. PMID9168109. S2CID4334033.
^Ax, P. (1985). "The position of the Gnathostomulida and Platyhelminthes in the phylogenetic system of the Bilateria". In Conway Morris, S.; George, J.D.; Gibson, R.; Platt, H.M. (eds.). The Origins and Relationships of Lower Invertebrates. Systematics Association Special Volume. Vol. 28. New York, NY: Clarendon / Oxford University Press. pp. 168–180. ISBN019857181X. OCLC59186778 – via Internet Archive (archive.org). proceedings of an international symposium held in London, September 1983ISBN9780198571810
^Nielsen, Claus (1995). Animal Evolution: Interrelationships of the living phyla. Oxford University Press. ISBN978-0-19-850682-9.