Echyridella onekaka

Echyridella onekaka is a species of freshwater mussel endemic to New Zealand. E. onekaka is an aquatic bivalve mollusc in the family Unionidae, the river mussels.

Taxonomy
The species was first recognised as a distinct species by Mark Fenwick and Bruce Marshall in 2006. It can be distinguished from Echyridella menziesii by a more strongly separated anterior pedal retractor muscle.

Distribution
Echyridella onekaka is found exclusively in the north-west of the South Island. It is the rarest known freshwater mussel species in New Zealand.