Classification and identification in the Teredinidae are based on the anatomy of the major organ systems, the shells, and particularly on the characters of the blade-like pallets which are used to plug the opening of the burrow when the siphons are retracted. Variations in the reproductive system and/or reproductive behaviour (among the most common and best documented isolating mechanisms in animals) are common in the teredinids and life history studies have shown that in at least four cases named forms which had been considered synonymous by Turner (1966) are separate species. Whilst most teredinids are oviparous (i.e. they release eggs which are fertilized externally), species of Lyrodus and Teredo are larviparous and may brood their larvae in the gills to the straight-hinge stage (short-term larviparous) or the pediveliger stage (long-term larviparous). These conditions are not easily distinguished except in adults carrying larvae in the gills. The problem of species with similar pallets but different life history patterns, first noted by Turner and Johnson (l971), was documented by Calloway and Turner (1984) for Lyrodus pedicellatus (Quatrefage 1849), a long-term sequential brooder and Lyrodus floridanus (Bartsch 1922), a short-term brooder. Subsequent studies showed that short-term brooders release their larvae en masse (synchronously) but that long-term brooders may have a single large brood and release the larvae synchronously or they may have two or more cohorts of larvae in different stages of development and release them in series, sequentially. By rearing larvae in the laboratory, by collecting and examining living adults with larvae and by histological studies we have now documented three additional species pairs: Lyrodus massa (Lamy 1923), short-term and Lyrodus singaporeana (Roch 1935) longterm synchronous; Lyrodus bipartitus (Jefferys 1860), long-term sequential and Lyrodus new sp., short-term; and Teredo furcifera (von Martens 1894), long-term synchronous and Teredo parksi (Bartsch 1921), short-term (Turner and Calloway, in preparation). These studies emphasize the fact that identification of teredinids, especially the brooders, can no longer be based solely on the pallets.

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