Prosomapoda

Prosomapoda is a clade of euchelicerates including the groups Xiphosura (horseshoe crabs) and Planaterga (a group comprising bunodids, pseudoniscids, chasmataspidids, eurypterids and arachnids), as well as several basal synziphosurid genera.^[1] The clade is defined by the lack of exopods (outer branches) of prosomal appendage II-V in the adult instar,^[1] where in contrast the exopods of appendage II-V are well-developed in the non-prosomapod euchelicerates Offacolus and Dibasterium.^[2][3]

Prosomapoda Temporal range: Ordovician–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Cryptocellus goodnighti, a ricinuleid arachnid
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Clade:	Euchelicerata
Clade:	Prosomapoda Lamsdell, 2013
Groups
†?Borchgrevinkium †Synziphosurina Planaterga Xiphosura