Nautiloids from Tarutao and Langkawi Islands from the Thung Song Formation or its equiva- lents were described by Stait and Burrett (1984b) and Stait et al. (1987), who considered earlier literature.All are described as shallow water assemblages.The faunas range in age from the mid-Ibexian to Whiterockian (approxi- mately Arenig-Llanvirn), and are quite diverse. Nautiloid-bearing limestones of this kind extend along the whole length of Sibumasu (Ingavat et al., 1975, Kobayashi, 1961, 1984). The faunas have been compared at the generic level with those of the North China platform and the Georgina basin, western Queensland. In view of the lithological similarities between the palaeotropical limestones in these areas this is perhaps not surprising.