Hyboclypus has often been placed in the Galeropygidae Lambert, 1911, together with Aulacopygus and Galeropygus. The compact apical disc of Galeropygus, coupled with long phyllodes that stretch over much of the oral surface, suggest its affinities lie with the cassiduloids. The elongate apical disc of Hyboclypus and Aulacopygus places these taxa as basal within the Atelostomata.
Hyboclypus and Aulacopygus are distinguished on differences in the structure of their apical systems. In both, the apical disc is elongate, with complemental plates separating genital plates 1 and 4. However, in Aulacopygus the complemental plates also completely separate oculars II and IV, whereas in Hyboclypus such complemental pales only partially separate oculars II and IV. It is worth noting, however, that Kier (1962, p. 29) did not believe this difference to be of generic significance, and considered Hyboclypus the senior subjective synonym of Aulacopygus. Spatoclypus also has an elongate apical disc and an anal sulcus, but differs in having the posterior ocular plates separated from the remainder of the apical disc.
Barras, C. 2006. British Jurassic irregular echinoids. Monograph of the Palaeontographical Society, 1-168, pls 1-14 (publication number 625).
Kier, P. M. 1962. Revision of the cassiduloid echinoids. Smithsonian Miscellaneous Collections 144 (3), 262 pp.
Jesionek-Szymanska, W. 1963. Echinides irreguliers du dogger de pologne. Acta Palaeontologica Polonica 8, 293-397, pls 1-7.