Remarks on the black and red squirrels allied to Sciurus prevosti. F.N. Chasen and C.B. Kloss. Records of the Raffles Museum, No. 11
This short note by F. N. Chasen and C. Boden Kloss (1925) addresses the taxonomic placement of black-and-red squirrel forms in Sumatra and Borneo that have been variously described as distinct species or races of Sciurus prevosti.
The authors argue that the black-and-red squirrel of northern Sumatra (S. piceus Peters) is a strongly differentiated race of S. prevosti, linked to the typical three-coloured form by the intermediate S. nyx Miller from Rupat Island, which retains a vestigial buffy side stripe (p. 98). In Borneo the situation is more complex: S. pluto Gray (from Sabah, Kinabalu, and Gantian) and S. rufoniger Gray (from Labuan) represent two colour phases that may be dimorphic forms of a single species, each divisible into geographic races (p. 99). The authors note the taxonomic difficulty of naming these forms—whether to treat them as races of prevosti or of rufoniger (which has priority)—and conclude that the Bornean black-and-red squirrel is likely not specifically distinct from its Sumatran counterpart, though further distributional data are needed (p. 99).