The baculum in the Vespertilioninae (Chiroptera: Vespertilionidae) with a systematic review, a synopsis of Pipistrellus and Eptesicus, and the desriptions of a new genus and subgenus

Current classification of the Vespertilioninae rests chiefly on a suite of mainly adaptive characters, among which facial shortening throughout the subfamily with consequent changes in the structure, size, relative position and number of the incisive and premolar teeth features prominently. Such characters may not necessarily reflect relationships or phyletic diversity, and sometimes do not serve properly to distinguish the genera that they purport to define, as in the distinction of Pipistrellus and Eptesicus, where generic boundaries remain unclear. The search for possibly less strongly adaptive features suggested the possibility that the morphology of the os penis or baculum might prove valuable in the study of the systematics of these genera and perhaps in the subfamily as a whole.This paper reviews earlier studies of the baculum in the Chiroptera and their relevance to systematics in the Order, with an examination of its gross morphology throughout the Vespertilioninae, especial attention being given to species currently allocated either to Pipistrellus or to Eptesicus. A synoptic review of the species content of these genera is presented, with the recognition and definition of subgenera and included species groups: three such (pumilus, capensis and tenuipinnis) currently referred to Eptesicus on dental grounds seem instead more closely related to Pipistrellus to which they are here transferred. One subgenus of Pipistrellus is described as new (p. 250).The Vespertilioninae as a whole display a wide range of bacular variation, which falls into two major and several minor groups. This has suggested a revision of the current classification of the subfamily, combining bacular features with those conventionally in use. Bacular morphology provides a clear indication that the ’Nycticeini’ (or ’Nycticeiini’) is an artificial grouping and that the genus Nycticeius as presently understood is composite. Currently it is held to include two species, the North American humeralis and the African schlieffenii: these are here thought to be sufficiently characterised to justify generic separation and a new generic name is proposed for schlieffenii (p. 254).A suggested classification of the subfamily is presented, with a tabulated review of earlier classifications; possible relationships between the constituent genera are discussed and the zoogeography of the bacular types within the subfamily is examined.