Belongs within: Echinozoa.
Contains: Orthopsidae, Echinacea, Irregularia, Diadematoida, Pedinidae.
The Euechinoidea are a clade of sea urchins ancestrally characterised by the presence of external gills.
Characters (Moore 1966): Test composed of five bicolumnar ambs and five alternating bicolumnar interambs. Plates imbricating, or joined by flexible integument, or (more usually) united by rigid sutures. Anus and surrounding periproct either placed within apical system (endocyclic condition) or secondarily translocated to interamb 5, which is termed posterior interamb (exocyclic condition). Lantern present or absent, or present only in juvenile stage. Gills and gill slits present or absent. Spheridia present. Pedicellariae present, including ophicephalous types.
<==Euechinoidea [Aulodonta]
|--AcroechinoideaSG93
| |--+--EchinaceaB01
| | `--IrregulariaB01
| `--DiademataceaSG93
| |--DiadematoidaB01
| |--Micropyga Agassiz 1879F66 [=Rotapedina Lambert & Thiéry 1914F66; Micropygidae, MicropygoidaSG93]
| | `--*M. tuberculata Agassiz 1879 [=*Rotapedina tuberculata]F66
| `--Pedinoida [Pedinina]SG93
| | i. s.: Leptocidaris Quenstedt 1858F66
| | `--*L. triceps Quenstedt 1858F66
| | Farquharsonia Currie 1927F66
| | `--*F. somaliensis Currie 1927F66
| `--PedinidaeF66
`--Echinothurioida [Echinothuriacea, Echinothurioidea]B01
|--Pelanechinidae [Pelanechininae]SG93
| |--Pelanodiadema oolithicum Hess 1973SG93
| `--Pelanechinus Keeping 1878F66
| `--*P. corallinus (Wright 1856) [=Hemipedina corallina]F66
`--Echinothuriidae [Asthenosominae, Echinothuriinae]F66
|--Phormosomatinae [Phormosomatidae, Phormosominae]F66
| |--Hemiphormosoma Mortensen 1934F66
| | `--*H. paucispinum Mortensen 1934F66
| |--Paraphormosoma Mortensen 1934F66
| | `--*P. alternans (de Meijere 1902) [=Phormosoma alternans]F66
| `--Phormosoma Thomson 1872F66
| |--*P. placenta Thomson 1872F66 [incl. P. sigsbei Agassiz 1880D05]
| |--P. bursariumF66
| |--P. rigidum Agassiz 1881MG-H11
| `--P. verticillatumBO01
`--Echinothuriinae [Asthenosominae]F66
|--Echinothuria Woodward 1863F66
| `--*E. floris Woodward 1863F66
|--Calveriosoma Mortensen 1934 [incl. Calveria Thomson 1872 (preoc.)]F66
| `--*C. hystrix (Thomson 1872) [=Calveria hystrix]F66
|--Hapalosoma Mortensen 1903F66
| `--*H. pellucidum (Agassiz 1879) [=Asthenosoma pellucidum]F66
|--Hygrosoma Mortensen 1903F66
| `--*H. petersii (Agassiz 1880) [=Phormosoma petersii]F66
|--Sperosoma Koehler 1897F66
| `--*S. grimaldii Koehler 1897F66
|--Asthenosoma Grube 1868 [incl. Cyanosoma Sarasin 1886]F66
| |--*A. varium Grube 1868 [incl. *Cyanosoma urens Sarasin 1886]F66
| `--A. striatissimum Ravn 1928SG93
|--Tromikosoma Mortensen 1903 [incl. Echinosoma Pomel 1883 non Audinet-Serville 1839]F66
| |--*T. kochleri Mortensen 1903F66
| `--T. panamenseF66
`--Araeosoma Mortensen 1903F66
|--*A. fenestratum (Thomson 1872)F66 (see below for synonymy)
|--A. bruennichi Ravn 1928SG93
|--A. mortenseniF66
|--A. owstoni Mortensen 1904MG-H11
|--A. thetidisF66
`--A. violaceumF66
Euechinoidea incertae sedis:
Bursulella Jones 1887B01
`--*B. triangularis Jones 1887B01
OrthopsidaeFP66
Trichodiadema Agassiz 1863 (n. d.)A66
Heterocidaris Cotteau 1860 [incl. Heteroechinus Quenstedt 1874; Heterocidaridae]F66
|--*H. trigeri Cotteau 1860F66
|--H. bruni Lambert in Lambert & Thiéry 1925SG93
|--H. dumortieri Cotteau 1871SG93
`--H. taylorensis (Clark 1893) [=Cidaris taylorensis]SG93
Serpianotiaris Jeannet in Peyer 1933F66
`--*S. hescheleri Jeannet in Peyer 1933F66