This taxon may be the small cryptic species of R. macrotis described by Sun et al. (2008).
· Dorsal fur is light brown. Ventral fur is buffy.
· Forearm length 39.2 - 45.4 mm (n = 22), mass 5.5 - 6.4 g (n = 10). 22 bats could be readily assigned to this taxon, and there was no overlap with either forearm length or FMAXE of the larger R. macrotis.
· The horseshoe is wide, covering the muzzle and is distinctly notched in the middle. A secondary noseleaf is present, but this is often concealed by the horseshoe. The sella is long, rounded and broad. The connecting process is high. The lancet is long with convex lateral margins and a rounded tip. Essentially a small version of R. macrotis.
· Little known
· We recorded bats from Fujian, Guangxi, Guizhou, Jiangxi, and Yunnan. R. siamensis appears to be widespread in southern China, and was recorded more frequently than R. macrotis, which may extend further northwards given our new record from Beijing. The two species were sympatric in Guangxi. R. siamensis was previously recorded from Yunnan according to Smith and Xie (2008).
· Little known.
· Generally roosts in caves and mines. Usually found in small numbers.
· This species often shares cave roosts with other bat species.
· Most rhinolophid bats have wing shapes that make them adept at foraging in cluttered environments.
·Little known.
·Echolocation calls had frequency of most energy ranging from 60-69.3 kHz (n=22).there was no overlap with frequencies emitted by the larger R. macrotis.
· There is no estimation of population size in China.
· Thai horseshoe bats are LC in the China Species Red List. IUCN Global Status is LC.
· Caves and forests should be protected as important habitats.