New genus and species of giant rat from Alor Island, Indonesia

Abstract

Gigantism is a common phenomenon observed in murids from islands, particularly the Indonesian islands belonging to the Lesser Sunda chain. Rats in this island group are often considerably larger than their continental sister taxa and have been reported from the islands of Timor, Sumba, and Flores. Here, we describe the first record of a giant rat from the island of Alor, at the northeastern end of the Lesser Sundas. Alormys aplini gen. et sp. nov. is described from isolated molars and a partial lower jaw from excavations in the twilight zone of Makpan Cave, a lava tube cave situated on the southwestern margin of the island. Speleological and taphonomic information suggests that these remains were deposited as a result of owl activities. Alormys aplini is characterized by its large size relative to members of Rattus and a relatively unspecialized, moderately hypsodont dentition. Among the larger rodents of the Lesser Sunda chain, Alormys most closely resembles Milimonggamys and Papagomys. Carbon and oxygen isotope analysis indicates that it consumed C3 plants almost exclusively. Its extinction in the late Holocene appears coeval with the disappearance of Timor’s and Sumba’s giant rats and may be related to increased aridity and deforestation on these islands.