The ‘smallest megabat’, Balionycteris, enters the LRT

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).

Figure 1. Subset of the LRT focusing on the resurrected clade Volitantia, including dermopterans, pangolins, bats and their extinct kin.

Figure 1. Subset of the LRT focusing on the resurrected clade Volitantia, including dermopterans, pangolins, bats and their extinct kin.

Not surprisingly
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.

Figure 5. Balionycteris hanging from both sides of a slender branch by laterally-twisted feet.

Figure 2. Balionycteris hanging from both sides of a slender branch by laterally-twisted feet.

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.

Figure 2. Balionycteris skull. Note the short rostrum, as in related micro bats.

Figure 3. Balionycteris skull. Note the short rostrum, as in related micro bats.

Like microbats, 
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.


References
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.

wiki/Pteropus
wiki/Archaeopteropus
wiki/Rousettus
wiki/Balionycteris

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