Xiphosura

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Kingdom: Animalia
Subregnum: Eumetazoa
Cladus: ParaHoxozoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Cladus: Panarthropoda
Phylum: Arthropoda
Subphylum: Chelicerata
Classis: Merostomata
Ordo:
Subordines (2): Xiphosurida – †Synziphosurida

Xiphosura incertae sedis: †Belinuropsis

Xiphosura Latreille, 1802

• Xiphosures Latreille, 1802
• Xiphosura: Størmer, 1944 (nom. corr.)

• Lamsdell, J.C. 2013. Revised systematics of Palaeozoic ‘horseshoe crabs’ and the myth of monophyletic Xiphosura. Zoological Journal of the Linnean Society 167(1): 1–27. DOI: 10.1111/j.1096-3642.2012.00874.x . Reference page. 
• Rudkin, D.M.; Young, G.A. 2009: Horseshoe crabs – an ancient ancestry revealed. Pp. 25-44 in: Tanacredi, J.T. et al. (eds.) Biology and Conservation of Horseshoe Crabs, Part 1 DOI: 10.1007/978-0-387-89959-6_2
• Størmer, L. 1955. Merostomata. In: Moore, R.C. (ed.): Treatise on Inver­tebrate Paleontology, P, Arthropoda 2, P4–P41. Geological Society of America and University of Kansas Press, Lawrence, Kansas. DOI: 10.17161/dt.v0i0.5345 . [as subclass]

For more multimedia, look at Xiphosura on Wikimedia Commons.