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Trachypithecus popa sp. nov. Popa langur Holotype: NHMUK ZD.1914.7.19.3 (adult male, stuffed skin and skull, left zygomatic arch slightly damaged; Figures S4–S 6), collected by Guy C. Shortridge on 11 September 1913. Head-body length (HBL): 600 mm, tail length (TL): 800 mm, hindfoot length (HFL): 174 mm, ear length (EL): 33 mm, body mass (BM): 7.9 kg. Mitogenome GenBank accession No.: MT 806047. Type locality: Mount Popa, Myingyan District, Myanmar (N20°55’, E95°15’, 4 961 feet =1 512 m a.s.l.) (location 6 in Figures 1, 5). Paratypes: NHMUK ZD.1914.7.19.4 (adult male, stuffed skin and skull) collected at the type locality by Guy C. Shortridge on 27 September 1913. HBL: 580 mm, TL: 795 mm, HFL: 161 mm, EL: 32 mm, BM: 8.2 kg. NHMUK ZD.1914.7.19.5 (adult female, stuffed skin) collected at the type locality by Guy C. Shortridge on 3 September 1913. HBL: 540 mm, TL: 780 mm, HFL: 152 mm, EL: 30 mm, BM: 7.0 kg. NHMUK ZD.1917.4.24.1 (adult male, stuffed skin and skull) collected at South Zamayi Reserve, 60 miles north of Pegu by J.M.D. Mackenzie on 10 March 1916. HBL: 498 mm, TL: 795 mm, HFL: 168 mm, EL: 33.5 mm, BM: 7.7 kg. NHMUK ZD.1937.9.10.4 (subadult male, stuffed skin and skull) collected 30 miles northwest of Toungoo by J.M.D. Mackenzie on 8 January 1928. HBL: 508 mm, TL: 785 mm, HFL: 165 mm, EL: 31 mm. NHMUK ZD.1937.9.10.5 (subadult male, stuffed skin and skull) collected 30 miles northwest of Toungoo by J.M.D. Mackenzie on 8 January 1928. HBL: 509 mm, TL: 795 mm, HFL: 165 mm, EL: 31 mm. AMNH M-54 770 (juvenile male, skull) collected at Camp Pinmezali, Pegu Yoma by John C. Faunthorpe on 27 April 1924. RMNH MAM.59807 (adult male, stuffed skin with skull in situ) collected at Yado, Mount Cariani, Tounghoo (= Taungoo) District, Myanmar (800–1 000 m) by Leonardo Fea in December 1887 (field number: 40). HBL: 555 mm, TL: 750 mm. Etymology: The English name for Trachypithecus popa is Popa langur. Mount Popa is a major landmark of the Myingyan District in Myanmar, and the place where the designated holotype was originally collected. The specific name “popa” is used as a noun in apposition. Description: The species is dark brown or gray-brown on the dorsum, with a sharply contrasting gray or whitish venter. Hands and feet are black. From above the elbow, the arms on the dorsal side gradually darken to black hands. The pale underside extends onto the chin and down to the inner side of the arms and thighs. The tail is paler than the back, notably at the base and underside. The face is black with a wide fleshywhite muzzle and broad white rings fully encircling the eyes. The hairs on the head are raised to a crest or are at least long and irregularly structured, but with no parting or whorl behind the brows present. This crest of hair and the forward-facing whiskers give the head a rhomb-like shape (Figure 6, Supplementary Figures S4–S 6). Body measurements (median and range) are: males (n =5) HBL: 562 (498–600) mm, TL: 795 (775–858) mm, HFL: 168 (144–178) mm, EL: 32 (30.0–33.5) mm, BM: 7.9 (7.7–8.2) kg; females (n =3) HBL: 585 (540–589) mm, TL: 780 (720–784) mm, HFL: 156 (152–160) mm, EL: 30 (20–32) mm, BM (n =1): 7.0 kg (Supplementary Table S3). Diagnosis: Overall, Trachypithecus popa sp. nov. is externally more similar to T. phayrei than to T. melamera. Body coloration in all three species is variable, but generally more fawn in T. melamera and more brownish to gray in Trachypithecus popa sp. nov. and T. phayrei. In Trachypithecus popa sp. nov. and T. phayrei, but not in T. melamera, the pale venter sharply contrasts with the back. The hands and feet are black in all three species. In Trachypithecus popa sp. nov., the arms (dorsal side) gradually darken to the hands from above the elbow, while in T. phayrei, they gradually darken from below the elbow. In T. melamera, the lower arms are not darker than the upper arms. In Trachypithecus popa sp. nov. and T. phayrei, the hairs on the head are raised to a crest or are at least long and irregularly structured, while T. melamera has a whorl or a parting behind the brows. Whiskers are laterally directed in T. phayrei, but forward directed in Trachypithecus popa sp. nov. and T. melamera. The direction of the whiskers in combination with the hairs on the head gives the head of T. phayrei a triangular shape, versus a rhomb-like shape for Trachypithecus popa sp. nov. and a round shape for T. melamera. All three species have a fleshy-white muzzle, which is wider in Trachypithecus popa sp. nov. and T. melamera. In T. melamera, the white around the eyes is restricted to the inner side, while in T. phayrei, the white normally encircles the eyes fully, although it is sometimes restricted to the inner side. In Trachypithecus popa sp. nov., the eyes are always fully encircled with broad white eye-rings. Males of T. phayrei have significantly shorter tails than males of the other two species (Figure 3, Supplementary Tables S5–S6). Cranially, Trachypithecus popa sp. nov. has a slightly longer skull, especially relative to its width, than in T. phayrei and T. melamera; this is achieved by a slight anterior elongation of the facial region of the skull relative to these taxa, rendering Trachypithecus popa sp. nov. slightly more prognathic in lateral and dorsal views and creating a more rectangular shape of the bony palate in ventral view (vs. a more square palate in T. phayrei and T. melamera). The teeth are, on average, larger in Trachypithecus popa sp. nov. than in T. phayrei and T. melamera, and molar measurements are the clearest means for separating the skulls of this new taxon from its closest relatives (Supplementary Tables S3, S7; Figure 4, Supplementary Figures S2–S 3); in particular, the third molar (M3/m3) appears larger overall in Trachypithecus popa sp. nov. when skulls are directly compared. PCAs using molar measurements and combined craniodental measurements separated T. phayrei, T. melamera, and Trachypithecus popa sp. nov., but cranial measurements alone did not separate them (Figure 4, Supplementary Figures S2, S 3). Distribution: Between the Ayeyarwaddy and Thanlwin rivers in the central dry zone of Myanmar and into the western foothills of the Kayah-Karen Mountains (Figure 5). The northeastern limit is undefined (see Discussion), but the species may occur throughout the Kayah-Karen Mountains. This species is endemic to Myanmar. Conservation status: As evident from historical records (museum specimens and travel notes), the species was once widespread in the central dry zone of Myanmar. Only two of these populations are known to have survived (location 6: Mount Popa, location 8: Bago Yoma), while all others are considered possibly extirpated. However, during recent fieldwork, three new populations (locations 10–12) were discovered. At location 10, Myogyi Monastery, the langur population is estimated at 75–100 individuals (Quyet et al., 2019), but these langurs are probably hybrids between Trachypithecus popa sp. nov. and T. melamera. The populations at location 11, Panlaung-Pyadalin Cave Wildlife Sanctuary, and location 12, Mount Yathae Pyan, consist of 46–96 individuals (Quyet et al., 2019) and 20–30 individuals (A.K.L. and A.L. pers. observation), respectively. The population at Bago Yoma (location 8) contains about 22 individuals (A.K.L. pers. observation) and at Mount Popa (location 6), field surveys conducted in 2019 revealed a population size of 111 individuals (Thaung Win pers. communication). Mount Popa was declared a national park (Popa Mountain Park) in 1989 and has an area of 128.54 km 2, including 26.97 km 2 classified as suitable to highly suitable for langurs (Thant, 2013; Thant et al., 2013). Throughout its range, Trachypithecus popa sp. nov. is threatened by hunting, habitat loss, degradation, and fragmentation caused by agricultural encroachment, illegal/unsustainable timber extraction, and disturbances caused by collection of non-timber products and free cattle grazing (Quyet et al., 2019; Thant et al., 2013). Considering a total population size of 199–259 individuals (excluding the possible hybrid population at Myogyi Monastery) in the four disjunct populations and the dramatic habitat loss over the last century, we propose to classify Trachypithecus popa sp. nov. as Critically Endangered (CR) as it meets the IUCN Red List criteria B1a and B1b (i-v) (IUCN, 2001). Furthermore, Trachypithecus popa sp. nov. needs to be added to the national and international lists of threatened species (IUCN, CITES). Improved protected area management, in particular improved law enforcement, in Popa Mountain Park and Panlaung-Pyadalin Cave Wildlife Sanctuary is essential to stabilize the two largest known populations. Mount Yathae Pyan is an isolated karst hill. This population could be protected through the designation of a community-protected area (CPA). The population status of the species in Bago Yoma is poorly understood and additional surveys are urgently required. The forests in Bago Yoma are severely degraded and fragmented, but could still provide the largest, contiguous habitat if deforestation and forest degradation are reversed through improved forest protection and restoration. Comments: Except for species of the T. pileatus group, the natal coat of Trachypithecus spp. is generally yellowish, orange, or light brown (Anandam et al., 2013; Rowe & Myers, 2016). Trachypithecus popa sp. nov. may be an exception as photos show an infant with creamy white fur coloration (Supplementary Figure S7).

Trachypithecus phayrei (Blyth, 1847) English name: Phayre’s langur. Synonyms: Presbytis barbei Blyth, 1863; Semnopithecus holotephreus Anderson, 1878. Distribution: East Bangladesh, Northeast India (Assam, Mizoram, and Tripura), and West Myanmar, west of the Chindwin and Ayeyarwaddy rivers (Figure 5). Conservation status: Currently listed as Endangered (Bleisch et al., 2008a), but reassessment required., Published as part of Roos, Christian, M. Helgen, Kristofer, Portela Miguez, Roberto, May Lay Thant, Naw, Lwin, Ngwe, Ko Lin, Aung, Lin, Aung, Mar Yi, Khin, Soe, Paing, Mar Hein, Zin, Nyein Nyein Myint, Margaret, Ahmed, Tanvir, Chetry, Dilip, Urh, Melina, Grace Veatch, E., Duncan, Neil, Kamminga, Pepijn, A. H. Chua, Marcus, Yao, Lu, Matauschek, Christian, Meyer, Dirk, Liu, Zhi-Jin, Li, Ming, Nadler, Tilo, Fan, Peng-Fei, Khac Quyet, Le, Hofreiter, Michael, Zinner, Dietmar & Momberg, Frank, 2020, Mitogenomic phylogeny of the Asian colobine genus Trachypithecus with special focus on Trachypithecus phayrei (Blyth, 1847) and description of a new species, pp. 656-669 in Zoological Research 41 (6) on page 664, DOI: 10.24272/j.issn.2095-8137.2020.254, http://zenodo.org/record/4395899, {"references":["Blyth E. 1847. Supplementary report of the curator of the Zoological Department. Journal of the Asiatic Society of Bengal, 16 (2): 728 - 732.","Blyth E. 1863. Catalogue of the Mammalia in the Museum Asiatic Society. Calcutta: Savielle and Cranenburgh.","Anderson J. 1878. Anatomical and Zoological Researches: Comprising an Account of the Zoological Results of the Two Expeditions to Western Yunnan in 1868 and 1875, and a Monograph of the Two Cetacean Genera, Platanista and Orcella. Volume 1. London: B. Quaritch.","Bleisch B, Brockelman W, Timmins RJ, Nadler T, Thun S, Das J, et al. 2008 a [2020 - 11 - 03]. Trachypithecus phayrei ssp. phayrei. The IUCN red list of threatened species 2008: e. T 136928 A 4350467. https: // dx. doi. org / 10. 2305 / IUCN. UK. 2008. RLTS. T 136928 A 4350467. en."]}