ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Accepted by M. Vences: 15 Jul. 2019; published: 15 Aug. 2019 545 Zootaxa 4656 (3): 545–571 https://www.mapress.com/j/zt/ Copyright © 2019 Magnolia Press Article https://doi.org/10.11646/zootaxa.4656.3.11 http://zoobank.org/urn:lsid:zoobank.org:pub:C465C40A-47AB-40D3-A7E6-E7B49FCAB131 Discovery of the westernmost population of the genus Ansonia Stoliczka (Anura, Bufonidae) with the description of a new species from the Shan Plateau of eastern Myanmar EVAN S. H. QUAH 1,2,6 , L. LEE GRISMER 2 , PERRY L. WOOD, JR. 3 , MYINT KYAW THURA 4 , JAMIE R. OAKS 3 & AUNG LIN 5 1 School of Biological Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia. E-mail: evanquah@yahoo.com 2 Herpetology Laboratory, Department of Biology, La Sierra University, 4500 Riverwalk Parkway, Riverside, California 92515, USA. E-mail: lgrismer@lasierra.edu 3 Department of Biological Sciences & Museum of Natural History, Auburn University, Auburn, Alabama 36849, USA E-mail: jro0014@auburn.edu; perryleewoodjr@gmail.com 4 Myanmar Environment Sustainable Conservation, Yangon, Myanmar. E-mail: mgmyint.banca@gmail.com 5 Fauna and Flora International, No(35), 3rd Floor, Shan Gone Condo, Myay Ni Gone Market Street, Sanchaung Township, Yangon, Myanmar. E-mail: aung.lin@fauna-flora.org 6 Corresponding author Abstract A new species of Ansonia is described from the Shan Plateau of Myanmar based on an integrative taxonomic analysis that differentiates it from all other congeners. Molecular phylogenetic analyses based on the mitochondrial genes 12S and 16S rRNA and tRNA-val recover A. kyaiktiyoensis sp. nov. as the sister species to A. inthanon from Thailand but differs from it and other congeners by at least a 5.0% sequence divergence. It is further differentiated by the following combination of morphological characters: (1) maximum SVL 24 mm in males and females; (2) first finger shorter than second; (3) absence of interorbital and tarsal ridges; (4) presence of light-coloured interscapular spot; (5) presence of yellow rictal tubercle; (6) absence of wide, light-coloured patch below eye; (7) presence of large, discrete, bright-yellow submandibular spots along the underside of lower jaw; (8) iris yellow-gold; (9) presence of markings on the snout consisting of streaks below the eye to the lip, and on the canthus rostralis to the nostril; (10) dorsum grey-brown with orange-beige spots, a dark-brown X-shaped marking on the back surrounding the interscapular spot, and dark-coloured markings on rump; (11) fore- and hind limbs with orange-beige cross-bars; and (12) venter light-gray with yellow spotting, especially near flanks and underside of hind limbs. Ansonia kyaiktiyoensis sp. nov. is the westernmost known record for the genus and the only species west of the Salween Basin. Its discovery echoes the increasing number of herpetological discoveries being made in upland regions fringing the Ayeyarwady and Salween Basins. Key words: Burma, endemism, amphibian, phylogenetics, systematics, montane, Ayeyarwady Basin, Salween Basin Introduction The bufonid genus Ansonia Stoliczka, 1870 is currently represented by 33 species that collectively range from northwestern Thailand, southward through Peninsular Myanmar, the Thai-Malay Peninsula, and Sumatra, and east- ward to Borneo and the Philippines (Alacala & Brown 1998; Frost 2019; Grismer 2006a,b; Grismer et al. 2016; Iskandar & Mumpuni 2004; Malkmus et al. 2002; Sanguila et al. 2011; Wood et al. 2008). Of these, only A. thin- thinae Wilkinson, Sellas & Vindum from the northern Tanintharyi Division is known from Myanmar (Wilkinson et al. 2012). Most species of Ansonia have narrow distributions—especially true of many upland species that are restricted to specific peaks or mountain ranges (Chan et al. 2014; Davis et al. 2016; Grismer et al. 2016; Hertwig et al. 2014; Inger et al. 2017; Quah et al. 2011; Waser et al. 2017). During a recent herpetological survey of Kyaiktiyo, Mon State, Myanmar, two specimens of a Stream Toad (genus Ansonia) were collected that could not be assigned to any currently known species. Morphological analyses confirmed their placement in the genus Ansonia by having a relatively short SVL (maximum SVL 24 mm in males