Mortensen distinguished this taxon from other Echinothuriidae (except for some species of Tromikosoma) in having the primary ambulacral plate effectively split into two parts, the inner part having no pore-pair. In Tromikosoma there are no buccal notches or 'gills' whereas in Sperosoma the buccal notches are always evident. The two are however, undoubtedly closely related.
Mooi et al. (2004) have argued that the divided ambulacral plate is an artefact caused by fracturing of thin plates during collection and subsequent handling. In Mooi et al's (2004) cladistic analysis Spermosoma is shown to be a paraphyletic grade of species below a clade of Tromikosoma species. Given the paraphyletic nature of Sperosoma, it seems best to unite Sperosoma and Tromikosoma to form a single large monophyletic genus.
Koehler, R. 1897. Sperosoma grimaldii, nouveau genre d'Echinothurides. Zool. Anzeig. 20, 302-307.
Mooi, R., Constable, H., Lockhart, S. & Pearse, J. 2004. Echinothurioid phylogeny and the phylogenetic significance of Kamptosoma (Echinoidea: Echinodermata). Deep Sea Research II 51, 1903-1919.
Mortensen, T. 1935. A monograph of the Echinoidea. Volume 2, Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C.A. Reitzel, Copenhagen.