Belongs within: Phymosomatoida.
Thylechinus is a genus of echinoids known from the Upper Cretaceous to the Oligocene of Eurasia, northern Africa and South America (Fell & Pawson 1966).
Characters (from Fell & Pawson 1966): Test hemispherical, of moderate size. Ambulacral plates trigeminate. Apical system dicyclic, oculars usually widely exsert. Female (of type species) with sunken aboral marsupia in interambulacrals.
<==Thylechinus Pomel 1883 [incl. Cenchritechinus Lambert 1911, Terina Agassiz 1838 (n. n.)] FP66
|–T. (Thylechinus) FP66
| |–T. (*T.) said (Peron & Gauthier 1881) [=Cyphosoma said] FP66
| `–T. (T.) aublini FP66
|–T. (Mistechinus de Loriol 1897) [incl. Egyptechinus Lambert 1936] FP66
| |–T. (*M.) mayeri (de Loriol 1897) [=*Mistechinus mayeri] FP66
| `–‘*Egyptechinus’ cuvillieri Lambert 1936 FP66
|–T. (Orthechinus Gauthier 1889) FP66
| `–T. (*O.) tunetanus (Gauthier 1889) [=*Orthechinus tunetanus] FP66
`–T. (Orthocyphus Arnaud 1896) FP66
`–T. (*O.) pulchellus [=Cyphosoma pulchellus] FP66
*Type species of generic name indicated
REFERENCES
[FP66] Fell, H. B., & D. L. Pawson. 1966. Echinacea. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt U. Echinodermata 3 vol. 2 pp. U367–U440. The Geological Society of America, Inc., and The University of Kansas Press.