The taxonomy of Crepidula has a history of instability due to the low number of informative shell characters and their phenotypic plasticity. Molecular and developmental data show that Crepidula convexa sensu Hoagland 1977 is composed of two distinct species. Animals of
the northern species are relatively larger, and have darker shells and direct development, while animals from the Gulf of Mexico and southeastern Florida have smaller, pale spotted shells and produce pediveligers. C. convexa Say, 1822 is redescribed and a single neotype is designated
for C. convexa and C. glauca Say, 1822 to represent the northern species and to formalize the synonymy of these two names. The southern species, which is distributed throughout the Gulf of Mexico, is described as a new species, C. ustulatulina.
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