Yesterday we looked at how bats are able to
cling inverted to broad cave walls and narrow branches with their twisted feet.
Today we add
Balionycteris (Fig. 2), the ‘smallest megabat’ to the large reptile tree (LRT, 1670+ taxa, subset Fig. 1).
Balionycteris nests basal to two larger megabats (= fruit bats = flying foxes), Pteropus and Rousetta in the LRT. The megabat clade nests between two micro bats, extinct Icaronycteris and extant Rhinopoma, both of which have a long Chriacus-type free tail. Balionycteris does not share this trait, so I searched for a megabat with a long tail.
Such a bat exists in the long-tailed fruit bat (Notopteris macdonaldi ). As expected, it nests at the base of the megabits in the LRT. More on this transitional taxon soon.
Balionycteris maculatus (originally Cynopterus Thomas 1893; Matschie 1899; 5-6cm in length) is the extant spotted-winged fruit bat, the smallest megabat and (for one day, yesterday) the most primitive one in the LRT (details above). It can be readily distinguished from other small species of Pteropodidae by a single pair of lower incisors, 2 pairs of upper molars, and by characteristic pale spots on wing membranes, particularly on digit joints.
Balionycteris has short, broad wings and highly maneuverable flight. Balionycteris inhabits small cavities, but rarely cave entrances, and roosts singly, or in small groups. Note the premolars and molars have reduced cusps, convergent with edentates, whales, pangolins and other placental mammals.
Matschie P 1899. Die Fledermäuse der Berliner Museums für Naturkunde. 1. Megachiroptera 72: 80.
Thomas O 1893. On some new Bornean mammalia. Ann. Nag. Nat. Hist., S.6 (65):341-347.