Enigmonia aenigmatica Sowerby, a Motile Anomiid (Saddle Oyster)

Abstract

AMONG the most obscure of marine bivalves are the elongated anomiids which occur on the leaves and exposed roots of mangroves over an uncertain area in the tropical central Indo–Pacific, but certainly ranging from Malaya to the Philippines and to north-east Australia. According to Iredale¹, the original description, based on a single valve from the East Indies, is that of Chemnitz in 1795. He named it Tellina aenigmatica, but he was non-binomial and the earliest valid user was Sowerby, who in 1825 used the name Anomia aenigmatica. Later, Koch introduced the generic name, as it later turned out pre-occupied, Aenigma, Iredale² being responsible for its substitution in 1918 by Enigmonia. Individuals found on mangrove leaves (Fig. 1) are flat and oval; those on stems and roots are more elongate with the shell curved in the line of the long axis so as to conform with the surface. It is not known whether these are separate species or are growth forms.