In members of this genus there are robust, simple chaetae in which the articulation between shaft and blade is fused; these simple chaetae are usually dark enough to be seen under stereo microscope and are present in the middle buch of chaetae starting at about 12-15. Paragnaths are present, but only on the maxillary ring (closest to the jaws) of the eversible phayrnx. This species can be distinguished from the only other common member of the genus in southern Australia, Simplisetia aequisetis, by having 10 or fewer paragnaths on each of Areas II and III of the eversible pharynx, and these paragnaths are often a gold or brown colour (not dark). Simplisetia aequisetis occurs in estuarine conditions while Simplisetia amphidonta occurs in fully marine environments. Body up to about 3 cm long.
Coastal bays, occasionally intertidal but normally at depths of 3-15 m.
- DSE Advisory List : Not listed
- EPBC Act 1999 : Not listed
- IUCN Red List : Not listed