Stem group atelostomates with:
Jurassic (Aalenian to Oxfordian) of Europe
|Species Included||Just two genera are included here. Hyboclypus and Aulacopygus|
|Classification and/or Status||Irregularia, Microstomata, stem group Atelostomata
Informal grouping for a basal paraphyletic grade.
Hyboclypids are a basal paraphyletic grade sister group to all other atelostomates. Like disasteroids they have an elongate apical disc, and this fully encloses the periproct. This informal grade unites forms which primitively retain an anal sulcus. Spatoclypus is very similar in having an aboral periproct opening into a deep anal sulcus, but accessory plates separate the posterior oculars from the posterior genital plates.