Rediscovery of one of the very few ‘unequivocally extinct’ species of marine molluscs:Littoraria flammea(Philippi, 1847) lost, found—and lost again?

The littorinid gastropod Littoraria flammea has been widely quoted as one of only three or four marine molluscs believed to have become extinct in historic times. It is easily recognized by its delicate, elongate, striped shell. We review the literature and available museum material to show that its only recorded locality was Shanghai and that it has not been collected since about 1855. We report the rediscovery of this species in salt marshes near Shanghai, where the habitat is under threat from invasive Spartina. For the first time we describe the penis, pallial oviduct and radula. These are the same as those of L. melanostoma, previously recorded only from Fujian province and southwards, where its shell is different from that of L. flammea. We now report a population of L. aff. melanostoma from between Fujian and Shanghai, with shells of intermediate form and colour. Analyses of sequences of COI, 12S and 28S genes do not support separation of these two Littoraria species, in terms of either reciprocal monophyly or genetic distance. Present evidence suggests that L. flammea could be only a distinctive morphological form or extreme of a cline, at the northern limit of the range of L. melanostoma.