taxonID	type	description	language	source
FA2887C8CD478A7FFF4C41FEFDAE0E06.taxon	materials_examined	New material: Two adult males (VN 20 - 20200305.1, VN 20 - 20200305.2, vouchers, in ethanol) and one pregnant female (VN 20 - 080, voucher, in ethanol), 5 March 2020, secondary lowland mixed forest, Co To mountain, Tri Ton district, An Giang province (10.388637 oN, 104.995033 oE [AG 1, Figure 1]).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD478A7FFF4C41FEFDAE0E06.taxon	description	Morphology: The external characters and measurements of our specimens (FA: 54.5 ± 1.8 mm (52.5 – 56.1 mm), TIB: 31.6 ± 0.4 mm (31.3 – 32.0 mm) agree with published data for Megaderma spasma (52 – 62 mm: Kruskop 2013). Members of the Megadermatidae are easily distinguished from all other bats by their short and convex-sided vertical noseleaf, large ears joined (to differing extents), and a long bifid tragus. Megadema spasma differs from the closely related Lyroderma sinensis by its smaller size (FA: 54.5 ± 1.8 mm vs 68.4 mm), shorter vertical noseleaf with a rounded apex and distinctly convex sides, median ridges with wide heart-shaped base, and fusin of inner margins of ears fused at about 15 % or less of their height (Figure 2 A). Genetics: No sequences were generated for this species, as morphological identification was considered reliable and prior evidence indicates low genetic structure across Southeast Asia (e. g., Feng et al. 2025; Soisook et al. 2015).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD478A7FFF4C41FEFDAE0E06.taxon	biology_ecology	Echolocation: Consistent with published data for M. spasma in Vietnam (Furey et al. 2009; Győrössy et al. 2024 a), our bats emitted short, broadband, frequency-modulated (FM) calls with multiple harmonics (lowest frequency of the second harmonic: 37 – 40 kHz) (Appendix 4).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD498A73FF4C47A6FBE50B48.taxon	materials_examined	New material: Five adult males (VN 18 - 142, VN 18 - 144, VN 18 - 156 [16 May 2018], 20191204.8, 20191204.11 [04 December 2019], vouchers, in alcohol, skull extracted), one one adult male (VN 18 - 141 [16 May 2018], voucher, in alcohol) and four pregnant females (VN 20 - 088, VN 20 - 090, VN 20 - 091, VN 20 - 092 [18 March 2020], vouchers, in alcohol). All were collected in secondary lowland mixed evergreen forests, Co To mountain, Tri Ton district, An Giang province (central coordinates: 10.388637 oN, 104.995033 oE [AG 1, Figure 1]).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD498A73FF4C47A6FBE50B48.taxon	description	Morphology: Our specimens were identified as members of the R. pearsonii group, which includes four strikingly similar species — R. pearsonii Horsfield, 1851, R. yunanensis Dobson, 1872, R. thailandensis Wu, Harada & Motokawa, 2009, and R. chiewkweeae Yoshiyuki & Lim Boo Liat, 2005 — based on the following morphological characters: Externally, they are medium-sized horseshose bats with an FA of 51.7 – 52.8 mm (Table 2). The pelage is long and woolly, dorsally orangish-brown and ventrally lighter. The noseleaf structure includes a lancet that is broadly triangular and long, with nearly parallel, straight sides; the connecting process is low and broadly rounded in lateral view. The sella is relatively blunt at the tip, broader at the base, with a characteristic medial constriction, and lacks basal lappets. The horseshoe is wide, covering the muzzle, and the ears are moderately large (Figure 2 B). Craniodentally, the skull is large with a GLS of 25.39 ± 0.47 (24.89 – 26.00) mm and CCL of 21.79 ± 0.22 (21.60 – 22.13) mm and robust; the zygomatic width exceeds mastoid width. The rostrum profile is relatively low, and the frontal depression is shallow. Both the sagittal and supraorbital crests are well developed. The anterior median swellings are prominent, whereas the lateral swellings are less pronounced and the posterior swellings are relatively concave. The upper canine (C ¹) is strong and well developed. The second upper premolar (P ²) is small and situated within the tooth row. The second lower premolar (P 3) is small, slightly extruded from the toothrow (Figure 3 A; Table 2). Within the R. pearsonii group, R. pearsonii includes two recognized subspecies: R. p. pearsonii occurring across South Asia, China, and mainland Southeast Asia (excluding Cambodia and the VMD), whereas R. p. chinensis K. Andersen 1905 is endemic to eastern China (Bates et al. 2019; Hutson et al. 2019). Rhinolophus yunanensis is found widely across China, India, Myanmar, and Thailand (excluding southern Thailand) (Bates et al. 2019), whereas R. thailandensis has been recorded from northwest and southern Thailand (close to the border between Thailand and Malaysia) to southern Cambodia (Bokor National Park [10.695841 ºN, 104.050246 ºE]) (Bouillard 2020; Zhou et al. 2023) and R. chiewkweeae is endemic to the south of the Isthmus of Kra (Waldien 2019). Given this distribution, our bats from An Giang province (southern Vietnam) are tentatively conspecific with R. thailandensis in Bokor National Park, Cambodia. This preliminary identification is supported by: 1) geographic proximity (~ 100 km distance) and lack of physical barriers between the two sites; 2) high overlap with published measurements for Cambodian R. thailandensis (= R. pearsonii in Chheang et al. 2013) (FA: 51.7 – 52.8 mm vs. 51.5 – 53.6 mm; CCL: 21.60 – 22.13 mm vs. 21.30 – 22.02 mm; (Table 2).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD498A73FF4C47A6FBE50B48.taxon	biology_ecology	Echolocation: The constant frequency (CF) component of echolocation calls emitted by our bats (53.1 – 54.9 kHz) is comparable to that of Cambodian R. thailandensis (53.6 kHz: Chheang et al. 2013) (Table 2; Appendix 4). Genetics: Consistent with previous studies (Francis et al. 2010; Mao et al. 2010; Zhou et al. 2023), our COI sequence analyses support the monophyly of “ pearsonii group ”. Within this species group, multiple monophyletic lineages (PP = 0.75 – 1.0) — differing from each other by ≥ 2.7 % (p-distance) — can be identified (Figure 4). Among these, our two tentatively identified R. thailandensis individuals, one R. yunanensis (= R. thailandensis sensu Francis 2019) from southern Thailand, and three R. chiewkweeae from Peninsular Malaysia form a monophyletic lineage (PP = 1), which diverged by ≥ 9.3 % p-distance from the other lineages including samples from China to central Vietnam, Laos and northeastern Thailand. Within this group, our bats occupy a basal position and are divergent from the south Thailand and Malayan counterparts by 1.5 % and 2 % p-distances, respectively (Appendix 5).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD498A73FF4C47A6FBE50B48.taxon	discussion	Taxonomic notes: While chromosomal differences among Rhinolophus pearsonii, R. yunanensis, and R. thailandensis (species with overlapping distributions) were reported by Zhou et al. (2023), no cytogenetic data exist for R. chiewkweeae. Examination of additional specimens reveals extensive overlap in mensural data between the geographically adjacent sister species R. thailandensis and R. chiewkweeae (e. g., FA: 51.5 – 61.0 mm vs. 51.9 – 56.9 mm; CCL: 21.30 – 24.80 mm vs. 21.30 – 23.50 mm) and echolocation frequencies (FmaxE: 49.0 – 53.6 kHz vs. 53.6 – 54.7 kHz) (Chheang et al. 2013; Francis 2019; Hutson et al. 2019; Morni et al. 2016; Wu et al. 2009; Yoshiyuki & Lim 2005). This phenetic overlap undermines the reliability of morphological and acoustic characters proposed to distinguish the two species; a situation likely attributable to limited specimen availability at the time of initial description, as observed in other rhinolophid pairs such as R. rex and R. paradoxolophus (Tu et al. 2023). Consistent with this, our COI sequence analyses — while supporting previous indications of higher cryptic diversity within the pearsonii group (Francis et al. 2010; Zhou et al. 2023) — found low genetic divergence (p - distance ≤ 2 %) between allopatric populations currently classified as R. thailandensis (e. g., VMD, southern Thailand) and R. chiewkweeae (W Malaysia). This low genetic divergence suggests that R. thailandensis would represent a junior synonym of the older name R. chiewkweeae, should further evidence confirm their conspecificity.	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4A8A75FF4C45F7FF110868.taxon	materials_examined	New material: Three pregnant females (VN 19 - 114, VN 19 - 113, VN 19 - 106, voucher specimens, in alcohol, skull extracted), and three other females (VN 19 - 23, VN 19 - 83, VN 19 - 138, voucher specimens, in alcohol), 19 March 2019. All were collected in secondary lowland mixed evergreen forests, Co To mountain, Tri Ton district, An Giang province (central coordinates: 10.388637 oN, 104.995033 oE [AG 1, Figure 1). Morphology: Our specimens were assigned to the Rhinolophus macrotis complex, which encompasses R. macrotis s. str., R. osgoodi, R. siamensis, and R. episcopus s. l. based on the following diagnostic traits: measurements (FA: 41.8 – 44.5 mm; Sl: 17.3 – 18.9 mm), external features (very large ears, a long and broad tongue-shaped sella, and a well-developed lancet with a rounded tip), and cranial traits (long palatal bridge, weak upper canines, and well-developed anterior nasal swellings). More specifically, our bats keyed out as an undescribed subspecies of R. episcopus (referred to as R. cf. macrotis by Tu et al. (2017 b) in northern Vietnam (Liu et al. 2019, 2021): medium size (FA of 41.8 – 44.5 mm; SL of 17.3 – 18.9 mm; ML of 11.46 – 11.54 mm); ears large with a length of 23.3 – 23.8 mm; sella parallel-sided, width <3 mm, but significantly broader at base; interpterygoid space shallow and cone-shaped. Supplementary leaflet clearly visible; sella without basal lappets; lancet long, lateral margins convex with a rounded tip; connecting process high, lower part almost parallel with sella; skull slender and elongated with MB (8.63 – 8.75 mm) exceeding ZB (8.05 – 8.40 mm); anterior median swellings well inflated, long, and expanded anteriorly but reaching slightly beyond front of rostral wall (Table 2; Figures 2 C – 3 B).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4A8A75FF4C45F7FF110868.taxon	description	Echolocation: Our bats emitted calls with constant frequency components ranging between 56.2 and 57.6 kHz (Table 2; Appendix 4) which are comparable to those of individuals in the macrotis complex in northern Vietnam (52.0 ± 0.3 kHz) (Tu et al. 2017 b). Genetics: Our Bayesian tree reconstructed from Cytb sequences (Figure 5) supported the monophyly of “ R. macrotis ” group (PP = 1), which comprises R. rex, R. mashalli, and four sister species in the R. macrotis complex (R. macrotis s. str., R. osgoodi, R. siamensis, and R. episcopus s. l.). Within this group, the species R. marshalli was monophyletic (PP = 1) and appeared as the sister-group to all other representatives (PP = 0.84). Within the latter subclade, four lineages were distinguished (PP ≥ 0.75): R. rex and three other lineages, namely A, B, and C, each including individuals of two or three different species: cluster A (R. osgoodi + R. episcopus s. l.); cluster B (R. osgoodi + R. episcopus s. l. + R. siamensis); and cluster C (Nepalese / Indian R. macrotis s. str. + our newly sequenced bats) (Figure 5). The p - distances calculated from Cytb sequences showed that interspecific divergences between R. marshalli, R. rex, and R. macrotis s. l. of “ R. macrotis ” group ranged between 2.5 – 5.8 %, whereas those were 2.4 – 4.3 % among the three clusters (A, B, and C) of R. macrotis. Within cluster C, the genetic distances between our bats and Nepalese / Indian R. macrotis ranged from 3.0 – 3.3 %, although one specimen from Himachal Pradesh, northwestern India (GB: PQ 778192), diverged by 2.8 – 3.0 % from topotypic R. macrotis s. str. from Nepal and Meghalaya, northeastern India (sensu Chakravarty et al. 2020; Saikia et al. 2025) (Appendix 6). Taxonomic notes: The “ R. macrotis ” complex currently comprises four closely-related species in mainland Asia: R. macrotis, R. episcopus, R. osgoodi, and R. siamensis (Hutson et al. 2019; Liu et al. 2019, 2021). Three of these (R. episcopus, R. osgoodi, and R. siamensis in China, Laos, Vietnam, and Cambodia) show exceptionally low mtDNA variation but can be distinguished by morphological, acoustic, and nuDNA differences. These discordances were thought to result from multiple mitochondrial introgression events (Liu et al. 2019, 2021; Tu et al. 2017 b). Given their phenotypic similarities and geographical proximity, we expected our VMD specimens to cluster with congeners from Vietnam, Cambodia, Laos, and China. Contrary to this prediction, our Cytb analyses revealed a closer affinity to Nepalese / Indian R. macrotis s. str. While our mtDNA-based phylogenetic patterns require nuDNA confirmation (which would provide some new insights into the evolutionary history and taxonomic systematics of the R. macrotis complex), these findings suggest delimitation of R. episcopus, R. osgoodi, and R. siamensis from R. macrotis s. str. based solely on mtDNA (Liu et al. 2019; Tu et al. 2017 b) is uncertain.	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4A8A75FF4C45F7FF110868.taxon	distribution	Distribution and ecological notes: We tentatively treat our relict population as taxonomically distinct from R. episcopus s. l. and R. siamensis populations in Vietnam and neighbouring countries. Like sympatric rhinolophids at AG 1, this taxon is also forest-dependent. Although documented only from a single site (AG 1), the species likely inhabits nearby mountainous and / or karst areas within the VMD (e. g., AG 2 - 4, KG 1 - 3: Figure 1) and southern Cambodia, where similar conditions occur. Records of pregnant females in March indicate a breeding season from at least February to August, similar to insectivorous bats in Vietnam and Cambodia (Furey et al. 2011; Lim et al. 2018).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4C8A75FF4C4617FD540C90.taxon	materials_examined	New material: Two pregnant females (VN 19 - 24 [14 March 2019], voucher specimen, in alcohol, skull extracted; VN 19 - 110 [19 March 2019], voucher specimen, in alcohol) and one adult male (20191206.01 [06 December 2019], voucher specimen, in alcohol). All were collected in secondary lowland mixed evergreen forests, Co To mountain, Tri Ton district, An Giang province (central coordinates: 10.388637 oN, 104.995033 oE [AG 1; Figure 1).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4C8A75FF4C4617FD540C90.taxon	description	Morphology: The morphology and mensural data (FA = 42.5 – 45.9 mm; SL = 17.61 mm; ML = 11.27 mm; Table 2) of our bats match R. marshalli in Vietnam (Csorba et al. 2003; Kruskop 2013; Tu et al. 2017 b): supplementary leaflet absent; sella with conspicuous basal lappets; lancet greatly reduced, more or less triangular; internarial cup expanded sideways to form prominent leaflets; lateral margins of internarial cup merge with margins of sella; sella very long, leaf-like, approaching ears in length; connecting process with very wide base; ears enormous (length 23 – 27 mm) (Figure 2 D); skull slender and elongated with MB (8.96 mm) exceeding ZB (8.23 mm); anterior median swellings low, long, and well-expanded anteriorly beyond the front of the rostral wall.	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4C8A75FF4C4617FD540C90.taxon	biology_ecology	Echolocation: Consistent with our morphology-based identification, the constant frequency components of calls (45.4 – 46.2 kHz: Table 2, Appendix 4) are comparable to calls emitted by R. marshalli in northern Vietnam and China (ca. 44 kHz: Tu et al. 2017 b) or northern Cambodia (43.0 – 44.0 kHz: Furey et al. 2021), but higher than bats from the Da Lat plateau (34.1 ± 0.2 kHz: Son et al. 2021) or western Cambodia (36.6 kHz: Furey et al. 2021). Genetics: Our analyses of Cytb sequences show that our two R. marshalli specimens and their allies from China and northern Vietnam appear in a well-supported monophyletic lineage (PP = 1), basal to a reciprocally monophyletic clade (PP = 0.84) uniting R. rex and species of the R. macrotis complex, with an interspecific divergence of 3.9 – 5.8 %. Within R. marshalli, our bats form a distinct lineage (PP = 1), divergent from another lineage (PP = 1) comprising their Chinese and northern Vietnamese conspecifics by p - distances of 2.4 – 2.6 % (Figure 5; Appendix 6). Since these populations are allopatric, their genetic differences are likely attributable to geographical variation.	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4C8A77FF4C4107FC640C20.taxon	materials_examined	New material: one parous female (VN 19 - BT 2019: voucher specimen, in alcohol, skull extracted), 9 August 2019, roosting in a house surrounded by rice field, orchards and small pockets and strips of remnant mangrove, Phu Ngai commune, Ba Tri district, Ben Tre province (10.077162 oN, 106.636503 oE [BT 1, Figure 1]); eight pregnant females (released), two nulliparous females (VN 22 - 19, VN 22 - 22: voucher specimens, in alcohol, skull extracted), and three adult males (VN 22 - 13, VN 22 - 17, VN 22 - 23: voucher specimens, in alcohol, skull extracted), 9 Febuary 2022, hollow cracks under the foundations of buildings in the centre of My Phuoc Melaleuca Forest, My Tu district, Soc Trang province (9.575333 oN, 105.751368 oE [ST 1: Figure 1]).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4C8A77FF4C4107FC640C20.taxon	description	Morphology: The morphology of our bats clearly distinguishes them from all Hipposideros species previously recorded in Vietnam, Cambodia and Laos (Furey et al. 2021; Kruskop 2013) and matches the diagnostic characters of H. kingstonae described by Wongwaiyut et al. (2023). Externally, our specimens are small-sized hipposiderids with an average forearm length of 38.2 mm (range 37.0 – 40.3 mm: Table 2). The pelage is relatively uniform dark brown, with hairs darker at the tips and paler at the bases. The noseleaf is characterized by an anterior leaf with a deep V-shaped median notch, absence of a lateral leaflet, and an internarial septum bearing a small median swelling (Figure 2 E). Craniodentally, the skull is small and elongated (GTL: 15.64 – 15.82 mm, CCL: 13.11 – 13.41 mm: Table 2). Mastoid width exceeds zygomatic width. In lateral profile, the skull is elevated over both the frontal and parietal regions of the braincase. The posterior rostral swellings are inflated and clearly set off from a narrow postorbital constriction. The sagittal crest is increasingly pronounced anteriorly, and the zygoma bear a well-developed dorsal process on their posterior sections. The dentition include a very small first upper premolar (P ²) situated within the tooth row; the upper canine and second upper premolar (P 4) do not contact; and the crown area of the first lower premolar (P 2) is approximately equal to that of the second lower premolar (P 4) but only about half its height (Figure 3 C).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4C8A77FF4C4107FC640C20.taxon	biology_ecology	Echolocation: The constant frequency component of echolocation calls emitted by free-flying and captured individuals at BT 1 and at ST 1 ranged between 142.0 – 144.0 kHz (Table 2; Appendix 4). This differs from Hipposideros spp. in Vietnam and neighbouring countries (Győrössy et al. 2024 a; Phauk et al. 2013) and matches acoustic data for H. kingstonae in the Thai-Malay Peninsula (Wongwaiyut et al. 2023). Genetics: Consistent with our morphological and acoustic identification, the COI and Cytb sequences of our Vietnamese H. kingstonae and allies from either Thailand or Malaysia (Sabah) in GenBank formed a monophyletic lineage (PP = 1), distantly related to other Southeast Asian Hipposideros (Figure 6). Genetic divergences within the H. kingstonae lineage are notably low (COI: ≤ 2.0 %; Cytb: ≤ 3.4 %) and contrast with substantially higher variation between H. kingstonae and congeners (COI: 3.3 – 16.7 %; Cytb: 6.0 – 13.9 %; Appendix 7).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4E8A69FF4C42DFFD240DD4.taxon	materials_examined	New material: one adult male (VN 18 - 143 [16 May 2018], voucher, in alcohol, skull extracted), two released lactating females (VN 18 - 121, VN 18 - 189, [16 May 2018]) and two pregnant females (VN 19 - 49 [15 March 2019], VN 20 - 0087 [03 March 2020], vouchers, in alcohol); five adult males (VN 19 - 50, VN 19 - 51, VN 19 - 52 [15 March 2019], VN 19 - 63, VN 19 - 64 [16 March 2019], vouchers, in alcohol); four adult males (20191203.1, 20191203.3, 20191204.3, 20191204.4 [3 - 4 December 2019], vouchers, in alcohol). All were collected in secondary lowland mixed forests, Co To mountain, Tri Ton district, An Giang province (10.388637 oN, 104.995033 oE [AG 1, Figure 1]).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4E8A69FF4C42DFFD240DD4.taxon	description	Morphology: Mensural data from our specimens (e. g., FA = 48.1 ± 1.0 mm, range 46.5 – 50.0 mm; CCL = 14.96 mm; Table 2) accord with published measurements for H. galeritus from Vietnam (FA: 45 – 51 mm; CCL: 14.6 – 15.8 mm) (Kruskop 2013) and Southeast Asia (FA: 47.8 ± 1.68 mm; CCL: 14.46 ± 0.28 mm) (Srinivasulu et al. 2025). External characters also match previous descriptions: the noseleaf is broad, covering the entire muzzle. The anterior leaf lacks a medial emargination and possesses two well-developed supplementary leaflets; the proximal leaflets are expanded and fused to form a single, impaired structure surrounding the anterior leaf which considerably exceeds it in width. The intermediate leaf is simple, equal to or wider than the posterior leaf. The posterior leaf is subdivided into four septa. Males possess a frontal sac behind the posterior leaf. The ears are triangularly pointed and the antitragal lobe is subangular, approximately one-third of the ear length. The pelage is thick and soft, dark to reddish brown dorsally, paler ventrally; hairs have pale bases. The muzzle and ears are variably pigmented (Figure 2 B). The skull is small and elongated (GLS = 17.66 mm), with the mastoid width exceeding zygomatic breadth (Table 2). In lateral profile, the skull is elevated over the frontal and parietal regions of the braincase. The sagittal crest is low, moderately developed anteriorly but indistinct posteriorly, extending into the parietal region. The lambdoid crests are weakly developed. The interorbital region is narrow. Three pairs of rostral inflations are present: the anterior rostral chambers are similar in length to the posterior-median rostral chambers. The posterior-lateral chambers are much wider than kidney-shaped posterior-median chambers. The dentition includes robust and tall upper canines; the small first upper premolars (P ²) situated within the toothrow between the upper canines and second upper premolars (P 4); and the crown area of the first lower premolar (P 2) is approximately equal to that of the second lower premolar (P 4) but only about half its height (Figure 3 B).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4E8A69FF4C42DFFD240DD4.taxon	biology_ecology	Echolocation: The constant frequency (CF) component of echolocation calls emitted by our bats ranged between 84 – 85 kHz (Table 2; Appendix 4). As tabulated in Srinivasulu et al. (2025) and our own data, only populations of H. galeritus found in the Thai-Malay peninsula and Bokor National Park, Cambodia (close to the AG 1) are known to emits calls at similar frequencies (80.7 – 92.0 kHz and 86 – 87 kHz respectively), whereas populations elsewhere in mainland Southeast Asia and on Borneo produce significantly higher constant frequency components (typically ≥ 98 – 110 kHz). Genetics: Consistent with previous studies (Francis et al. 2010; Murray et al. 2012; Srinivasulu et al. 2025), our Bayesian trees based on COI and Cytb datasets strongly support the monophyly of Southeast Asian H. galeritus s. l. (PP = 1). In our COI tree, the H. galeritus s. l clade is subdivided into three well-supported geographic subclades (PP = 1): A – insular Sundaic (Borneo (Kalimantan, Indonesia and Sarawak, Malaysia) + Java), B – mainland Sundaic or the Thai-Malay Peninsula, and C — Indochinese comprising Thailand excluding the peninsula, Cambodia, Laos, Vietnam, including our specimens in the VMD. In our Cytb tree, bats from insular Sundaic and Indochinese subregions appeared in two divergent and highly supported lineages (PP = 1) (Figure 6). Genetic divergences based on COI / Cytb sequences within three recognized subclades A, B, C Southeast Asian H. galeritus s. l. are between 0 – 4.9 % / 0.3 – 2.8 %, 0.3 / –, and 0 – 2.7 / 0.2 – 0.9 %, respectively; distances between these clades are between 11.4 – 14.6 % / 10.7 – 11.5 % and comparable with interspecific variations in the Hipposideros genus (Appendix 7).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD4E8A69FF4C42DFFD240DD4.taxon	discussion	Taxonomic notes: Hipposideros galeritus was historically regarded as a widespread species across the Indomalayan Region, comprising four geographic subspecies: H. g. galeritus (distributed in the Thai-Malay peninsula, including Tarutao, Penang, and Bangka islands, Sumatra, SE Thailand, S. Laos, Cambodia, and C-S. Vietnam), H. g. brachyotus Dobson, 1874 (India, Bangladesh, Sri Lanka), H. g. insolens Lyon, 1911 (endemic to Borneo), and H. g. longicauda Peters, 1861 (restricted to Java) (Corbet & Hill 1992; Monadjem et al. 2019; Simmons 2005). Based on analyses of COI gene sequences, morphological and acoustic data, Srinivasulu et al. (2025) revised this classification by: (1) re-elevating brachyotus to species rank for Indian populations, (2) describing the Sri Lankan population as H. srilankaensis, and (3) concluding that Southeast Asian H. galeritus s. l. represents several distinct species. This conclusion aligns with earlier studies (Francis et al. 2010; Murray et al. 2012) which found substantial genetic divergence and distinct echolocation call frequencies among allopatric populations (e. g., ~ 115 kHz in Borneo, 89.1 ± 1.5 kHz in Peninsular Malaysia, ~ 108 kHz in Laos), supporting their status as evolutionarily and ecologically distinct species. However, Srinivasulu et al. (2025) interpreted the observed call frequency variation across Southeast Asian COI lineages as vocal plasticity. Our genetic results confirm deep geographic structuring within Southeast Asian H. galeritus s. l. but delimiting these taxa and elucidating their evolutionary history remains challenging. For instance, despite similar isolation by marine barriers, COI p-distances between one Javan and two Bornean bats were unexpectedly low (4.7 – 4.9 %), contrasting sharply with higher divergences between insular and continental Southeast Asian populations (11.4 – 14.6 %; Appendix 7). These distances exceed maximum intraspecific variations in the Indochinese H. galeritus (pdistances ≤ 2.7 %) and interspecific variations between certain pairs of sister species such as 3.3 % between H. kunzi and H. kingstonae or 3.5 % between H. rotalis and H. khaokhouayensis. However, they are lower than the intraspecific variation between Bornean and Peninsular Malaysian populations of H. cervinus (5.9 – 6.2 %; Appendix 7). This pattern suggests allopatric populations in insular Southeast Asia either represent deeply structured populations of a single species or recently diverged sister species (Francis et al. 2010; Murray et al. 2012). Likewise, our low-frequency emitters in the VMD (AG 1: 84 – 85 kHz) are phylogenetically nested within the high-frequency Indochinese clade (~ 110 kHz), yet genetically divergent from the low-frequency emitters of the Thai-Malay Peninsula (mainland Sundaic subregion). While call plasticity may be a plausible explanation for frequency variation in the Indochinese subregion clade, these mtDNA phylogenetic patterns can stem from either incomplete lineage sorting of ancestral polymorphisms after diversification or introgression following secondary contact (Ballard & Whitlock 2004; Funk & Omland 2003). Long branches in the mtDNA phylogenetic tree, especially among the two phonic forms (excluding individuals showing potential introgression) indicate that these lineages have had substantial time to evolve independently after their divergence from a common ancestor. Instead, the “ low-frequency ” bats carrying mtDNA haplotypes of “ high-frequency ” congeners was not found randomly but specifically in parapatric zones (including AG 1 and KG 1 - 3 [Figure 1] and in Bakor National Park, Cambodia), suggesting historical or ongoing introgression between previously isolated incipient species following secondary contact (s) (Mao et al. 2010, 2013; Zhou et al. 2023). As proposed by Srinivasulu et al. (2025) and supported by regional phylogeographic studies (Khan et al. 2010; Tu et al. 2017 a, 2018 b), the evolutionary history of taxa within the H. galeritus s. l. complex in mainland Southeast Asia was likely shaped by climatic fluctuations and associated changes in forest range and sea levels during the Pliocene – Pleistocene. In line with this hypothesis, cycles of forest contraction and expansion, along with the submersion and re-emergence of the Isthmus of Kra due to sea-level oscillations, may have facilitated allopatric speciation, followed by secondary contact and asymmetric introgressive hybridization. Given the limitations of our study (incomplete geographic sampling, reliance solely on mtDNA markers), future research incorporating nuclear DNA data is needed to (1) test gene flow hypotheses and clarify species boundaries within mainland Southeast Asia; and (2) resolve the taxonomy and phylogeography of insular Sundaic populations (Borneo, Sumatra, Java, Sulawesi).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD508A6AFF4C438BFF060810.taxon	materials_examined	New material: One pregnant female (VN 19 - 53, voucher specimen, in alcohol), 19 March 2019, and two parous females (20191205.01, 20191205.02, voucher specimens, in alcohol), 5 December 2019, secondary lowland mixed forest, Co To mountain, Tri Ton district, An Giang province (10.388637 oN, 104.995033 oE [AG 1, Figure 1]).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD508A6AFF4C438BFF060810.taxon	description	Morphology: Our bats were unequivocally identified as Coelops frithii based on diagnostic characters provided by Kruskop (2013). They are small-sized bats with a FA of 38.4 – 39.2 mm. External tail virtually absent, interfemoral membrane slightly reduced, wings broad and rounded, terminal phalanges of 4 th and 5 th wing digits with conspicuous T-shaped cartilaginous apexes. Ears broadly rounded, with very well developed antitragal lobes, not separated by notches. Noseleaf rather simple, with reduced intermediate leaf and small posterior leaf not subdivided by median septa (Figure 2 G).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
FA2887C8CD508A6AFF4C438BFF060810.taxon	biology_ecology	Echolocation: Consistent with the previous studies (Győrössy et al. 2024 a; Ho et al. 2013; Huang et al. 2019 a), our bats emitted calls of varying structures, where the dominant energy in the second harmonic was typically concentrated in the FM sweep (ca. 160 kHz) rather than the very short quasi-constant frequency (QCF) component (192 – 194 kHz) preceding this (Appendix 4). Genetic s: Our Bayesian tree reconstructed from Cytb sequences show our bat (VN 19 - 53) nested well in a well-supported monophyletic lineage alongside its conspecifics from China and Taiwan. Genetic distances among our bats and their Chinese and Taiwanese allies ranged between 4.2 – 6.1 % (data not shown).	en	Tu, Vuong Tan, Furey, Neil M., Koyabu, Daisuke, Arai, Satoru, Görföl, Tamás, Ngon, Lam Quang, Nojiri, Taro, Fukui, Dai, Csorba, Gábor, Balvín, Ondřej, Tuan, Le Quang, Tuan, Tran Anh, Hang, Chu Thi, Hanh, Le Minh, Thi, Van Anh Le, Thien, Huynh Huu, Hassanin, Alexandre (2026): Bats of the Vietnamese Mekong Delta: A revised checklist with significant new records. Zootaxa 5768 (3): 301-334, DOI: 10.11646/zootaxa.5768.3.1, URL: https://doi.org/10.11646/zootaxa.5768.3.1
