Key to Heth species groups

1. With continuous collar of cervical spines, having only a minor interruption of larger lateral spines; lappets present or absent (Figs. 9, 10).......................................................................................... 2

- Cervical collar of spines discontinuous or absent; lappets absent................................................ 3

2. Lappets absent (Figs. 9, 10, 11D)........................................................... Group 1 Heth spp.

- Lappets present (Figs. 11, excluding 11D, 12)............................................... Group 2 Heth spp.

3. With discontinuous cervical collar (Figs. 13, 14)............................................... Group 3 Heth spp.

- Without clear cervical collar; lappets absent: not conforming to any other group description (Fig. 15)..... Group 4 Heth spp.