The Singapore rat is distinguished from other rats in Singapore by its sharply demarcated white underside, brownish throat and uniformly coloured tail. It inhabits secondary forest and scrubland (Baker & Lim, 2012: 140). The example featured here was most likely killed and flattened by the tyres of a motor vehicle while it attempted to cross the road from one forest patch to another.

The presence of this species in Singapore was first mentioned by Kottelat & Whitten (1996: 5 as Omobranchus meniscus). Omobranchus meniscus, described by Springer & Gomon (1975: 52) from Chantabun, Thailand, is a junior synonym of Omobranchus smithi (see Springer, 1981: 703). Omobranchus smithi is readily distinguished from its congeners by the black crescent-shaped mark extending dorsally from the posterior margin of the eye (Springer & Gomon, 1975: 52 as Omobranchus meniscus). The species was described from the Godavari Estuary in India, and has been recorded in Vietnam at Nha Trang Bay (Williams, 2014). Although very poorly known, it should be expected to occur along the mangrove coasts in between the known localities. The apparent rarity of this fish could be linked to its supposed preference for deep crevices. The specimen from Sungei Pandan was obtained from within a piece of timber.

Recorded in Singapore since 1852 (see Fowler, 1938: 191), Choerodon oligacanthus is among three species of tuskfishes known from Singapore waters. The other two are Choerodon anchorago, the anchor tuskfish, and Choerodon schoenleinii, the blackspot tuskfish (Fowler, 1938: 191-192). The Singapore tuskfish is distinguished from its two local congeners by its colour pattern which consists of bluish stripes on the lower sides of its body and the absence of a black spot on the middle of its dorsal fin. It occurs singly or in pairs over sand-rubble substrates next to coastal reefs in Indonesia (east Sumatra, Kalimantan and Sulawesi), Malaysia and the Philippines (Allen & Erdmann, 2012: 647)