Rhytidarex johnsoni is a species of land snail belonging to the family Rhytididae. It is endemic to ManawatÃÂwhi / Three Kings Islands, northwest of mainland New Zealand.
In the original description, Powell described the species as below:
The shells of the species have a diameter of (maximum of ), and a height of . The species resembles Rhytida greenwoodi, but can be identified due to having a narrowly rounded body whorl that is almost carinated at the shell periphery.
The species was first described by A. W. B. Powell in 1948 as Rhytida (Rhytidarex) johnsoni, who named it the type species of the subgenus Rhytida (Rhytidarex). When Rhytidarex was raised to genus status by Frank Climo in 1977, it remained the type species for the taxon. Powell named the species after Major Magnus Earle Johnson, one of the two collectors of the holotype, in recognition of his exploration of ManawatÃÂwhi / Three Kings Islands. The holotype of the species is held by the Auckland War Memorial Museum. Individuals on different islands have very little genetic diversity.
R. johnsoni is endemic to ManawatÃÂwhi / Three Kings Islands, known to occur on Oromaki / North East Island, Moekawa / South West Island and à Âhau / West Island. It is one of the widest distributed endemic land molluscs of ManawatÃÂwhi / Three Kings Islands. The species has been found in leaf litter associated with Meryta sinclairii.
Under the New Zealand Threat Classification System, this species is listed as "Naturally Uncommon".