TAXONOMY OF THAIS AND MORULA (MOLLUSCA : GASTROPODA : MURICIDAE) IN SINGAPORE AND VICINITY

Abstract

The taxonomy of intertidal muricid species in the genera Morula Schumacher, 1817 and Thais Röding, 1798 (Mollusca: Gastropoda: Muricidae) is revised for Singapore and peninsular Malaysia. Eighteen species of Thais and ten species of Morula are described from the rocky shores and mangroves of peninsular Malaysia. Of these, twelve species of Thais and seven species of Morula are found in Singapore waters. Four new species of Thais are also described. In addition, seven species not recorded from Singapore or peninsular Malaysia but found helpful in comparative studies, are also included. Synonymies, descriptions of the shell, operculum, radula and animal, notes on their habitat as well as their geographical distributions are given for each species. These are based largely on material collected by the author on the coasts of Singapore and peninsular Malaysia, and from material in various museums. The colour and pigmentation patterns within the shell aperture of many species were determined to be essential shell characters in identification. Anatomical characters such as foot pigmentation, penial shape and structure of the capsule gland were also found to be useful in delineating species. Egg capsules are described for nineteen species and their morphology used for taxonomic decisions. A preliminary clt1distic analysis based on animals obtained in this study revealed that Morula species form a well-defined, highly derived clade. The relationships between the different species of Thais and the outgroup however, are less clear.