Pipistrellus Kaup, 1829

Nishioka, Yuichiro, Nakagawa, Ryohei, Nunami, Shin & Hirasawa, Satoshi, 2016, Small Mammalian Remains from the Late Holocene Deposits on Ishigaki and Yonaguni Islands, Southwestern Japan, Zoological Studies 55 (5), pp. 1-21 : 13-14

Genus Pipistrellus Kaup, 1829

Material examined: A right mandible with C, M 1, M 2, and M 3 (MPM-Fo 2910).

Locality: Indeterminate layer, Umabana-zaki Fissure, Yonaguni Island.

Measurements: See Table 3.

Description: The mandible (MPM-Fo 2910) is smaller and deeper than that of Rhinolophus . The body is dorso-ventrally deep at the anterior relative to the posterior. The mental protuberance projects strongly toward the ventral side. A large mental foramen is situated below the canine. The ramus is deep dorso-ventrally, and has a large triangularshaped fossa with distinct masseteric crests.

The mandible preserves a canine and three molars. There are three small root sockets for incisors at the anterior of the canine. Although all premolars are broken, three alveoli are present between the canine and M 1. The first (anterior) alveolus forms a large socket, and is separated from the second alveolus. The second and third alveoli belong to a single premolar (P 4) because they are adjacent to each other. A tiny premolar represented by Rhinolophus species is absent. As a result, the mandible has a dental formula 3.1.2.3.

The lower canine forms as a claw and has an additional small cusp (a stylid) on the posterior side. The protoconid is moderately worn. The posterior stylid connects with the protoconid by a sharp cristid. The basal cingulum is sharp, as a V-letter line, in the buccal view. The tooth is anchored by a robust root.

The molars have the W-shaped occlusal pattern similar to those of Hipposideros turpis or of Rhinolophus perditus . The talonid basin is slightly larger than the trigonid basin. The hypoconid is prominent and approaches the buccal side. The entoconid is isolated from the hypoconulid by a gap. The hypoflexid is deep, forming a V-letter gap on the buccal side. The basal cingulum is strong on the anterior, buccal and posterior sides. The cingulum (entocingulid) on the lingual side is indistinct or absent. The crown size of M 2 is slightly larger than that of M 1. M 3 is reduced relative to M 1 and M 2. M 3 is characterized by the relatively small paraconid and wide hypoflexid. Each molar has two roots.

Remarks: Pipistrellus abramus has the lower dental formula, 3.1.2.3, without P 3, but shares many dental characteristics with the other genera of the Vespertilionidae ( Yoshiyuki 1989) . This family is one of great diversified bats in Japan, including 10 genera: Myotis , Pipistrellus , Eptesicus , Nyctalus , Vespertilio , Barbastella , Plecotus , M i n i o p t e r u s, M u r i n a, a n d Ta d a r i d a. A m o n g these, Myotis , Nyctalus , Vespertilio , Plecotus , and Miniopterus are different from Pipistrellus , in having two or three premolars single-rooted ( Abe 2000). The mandibular symphysis of Pipistrellus is short and straight (not drawing an arc). This feature distinguishes Pipistrellus from Eptesicus , Barbastella , Murina , and Tadarida , based on the illustrations of vespertilionid mandibles ( Abe 2000). The mental foramen below the canine is also diagnostic for Pipistrellus abramus , which is different from many other chiropterans ( Abe 2000).

Pipistrellus abramus is currently distributed in East Asia, including Yonaguni Island ( Kawai 2009). MPM-Fo 2910 is not different basically from P. abramus living in Japan, but the canine paraconid of the former is somewhat stronger than that of the latter. Some researchers consider that P. abramus in Japan is isolated from the continental species, P. javanicus (e.g., Yoshiyuki 1989; Volleth et al. 2001), but the difference between them is probably not clear at least in dental morphology.

Distribution: Southeast Asia, South Russia, Korea, China, Taiwan, and Japan (Honshu, Shikoku, Kyushu, Ryukyu Islands) ( Kawai 2009).