This species was originally named
Ricinula mutica by Lamarck in 1816, grouping it with species that are now mostly in
Drupa and
Morula. In 1823, Dall defined two new genera,
Drupina and
Morulina, to hold species of
Drupa and
Morula having simple non-plaited columnellae. He chose
R. mutica as the type species for
Morulina. Thiele in 1931 and Wenz in 1941 had placed
Morulina into
Drupa. In 1968, Emerson found that the teeth on the
radula of
D. mutica had an unusual shape. As a result, he desired to split it out to its own genus, but the name
Morulina was already taken as a genus of arthropod. Thus he introduced a new name
Azumamorula, recognising Masao Azuma who had extracted the radula specimen. In 2004, Houart placed
Azumamorula and
Oppomorus as subgenera of
Morula, and moved
Morula from subfamily
Rapaninae to Ergalataxinae. However, in 2013, a phylogenetic study of the sequences for four genes indicated that
Morula (Morula) sensu stricto was polyphyletic, and
Morula (Oppomorus) was a separate clade. The relevant genes from
A. mutica haven't been sequenced, but it's unlikely to be part of a more-restricted
Morula–Habromorula group. As of 2020, Houart lists
Azumamorula as a separate genus and Molluscabase classes the combination
Azumamorula mutica as "accepted". ==Notes==