1	Presence of a clump of dental papillae at the apex of the jaw (Fig. 2h, 10c)	3
–	Without dental papillae	2
2	One pair of infradental oral papillae on apex of jaw (Fig. 4c)	Amphiuridae
–	One apical papilla on apex of jaw (Fig. 9c, 13c)	4
3	A continuous series of oral papillae (Fig. 11c)	Ophiocomidae
–	Without oral papillae (Fig. 2h)	Ophiotrichidae
4	Disk and arms covered with a thick and naked tegument	Ophiomyxidae
–	Disk covered with scales, granules or spines	5
5	Two pairs of bursal slits in each interradius (Fig. 13b, g)	Ophiodermatidae
–	One pair of bursal slits in each interradius (Fig. 3b, 8b, 9b)	6
6	Disk covered only with scales. Oral papillae in continuous series	7
–	Disk covered by scales and spines. Presence of a diastema separating the lateral oral papillae from the apical papillae (Fig. 8b, i)	Ophiactidae
7	Dorsal scales of disk thin and imbricating (Fig. 9a, f, 10a, f). Genital papillae present or absent (Fig. 9b, 10b)	Ophionereididae
–	Dorsal scales of disk thick and imbricating (Fig. 3a). Dorsal arm plate present or absent	Ophiolepididae