Hipposideros besaoka is an extinct bat from Madagascar is the genus Hipposideros. It is known from numerous jaws and teeth, which were collected in a cave at Anjohibe in 1996 and described as a new species in 2007. The site where H. besaoka was found is at most 10,000 years old; other parts of the cave have yielded Hipposideros commersoni, a living species of Hipposideros from Madagascar, and some material that is distinct from both species. H. besaoka was larger than H. commersoni, making it the largest insectivorous bat of Madagascar, and had broader molars and a more robust lower jaw. As usual in Hipposideros, the second upper premolar is small and displaced from the toothrow, and the second lower premolar is large.
Taxonomy and DistributionEdit
In 1996, a team led by biologist David Burney collected breccias containing bats and other animals from the cave of Anjohibe in northwestern Madagascar. The bats in the sample were described by Karen Samonds (previously Irwin) in her 2006 Ph.D. dissertation and a 2007 paper. She found several living species in addition to two extinct ones, Triaenops goodmani and Hipposideros besaoka, that she described as new. Hipposideros, the genus to whichH. besaoka is assigned, contains the living species Hipposideros commersoni from Madagascar, among many others. The specific name besaoka is the Malagasy for "big chin". The material of H. besaoka is from locality TW-10 within the cave and is about 10,000 years old or younger. A cladistic analysis using morphological data suggests that H. besaoka is most closely related to the mainland African H. gigas and H. vittatus, previously included in H. commersoni, and somewhat more distantly to H. commersoni itself.
Samonds also found Hipposideros material in other sites at Anjohibe, but did not assign it to H. besaoka. In Old SE, also at most 10,000 years old, a single fourth upper premolar (P4) was found with dimensions different from those seen in both H. commersoni and H. besaokaand lacking a cusp on the front lingual (inner) corner, present in both other species; Samonds assigned this specimen to Hipposideros sp. cf. H. commersoni. In NCC-1 (estimated 69,600 to 86,800 years old), a lower incisor and a third lower molar (m3) were found; these teeth resemble H. commersoni and are distinct from H. besaoka, so Samonds assigned them to the former species. Locality SS2, which could not be dated, contained a few teeth and isolated jaws of Hipposideros. Some of these showed measurements distinct from both Hipposiderosspecies, rendering the assignment of the material doubtful; Samonds referred it to H. sp. cf. H. commersoni.
Hipposideros besaoka is known from numerous jaw bones and isolated teeth. The material is identifiable as Hipposideros by having one incisor, one canine, two premolars, and three molars in the upper dentition on both the left and right; two incisors, one canine, two premolars, and three molars in the lower dentition on the left and right; the second premolar is shifted out of the toothrow toward the side of the skull, so that the canine and premolar touch or nearly tough; and the second lower premolar is large and has a borad, steep facet on the buccal side. Morphometric analysis shows that H. besaoka is significantly different from H. commersoni and falls outside the substantial variation within that species. In particular, the upper molars are broader and the mandible is more robust. In bats, robust mandibles are often associated with a diet that includes hard objects. H. besaoka was the largest insectivorous bat of Madagascar, a position now filled by the smaller H. commersoni.