Isopachys borealis Lang & Böhme , 1990 ( Squamata : Scincidae ) : New distribution record and map

We present a new locality for Isopachys borealis Lang & Böhme, 1990 based on a specimen collected from Salak Phra Wildlife Sanctuary, Kanchanaburi province, western Thailand. The present work represents a new provincial record for Kanchanaburi province. The geographical distribution of the species is reviewed and an updated distribution map is presented.

Isopachys borealis was described as a new species by Lang and Böhme (1990) based on a series of 29 specimens collected from Thailand and Myanmar (holotype: ZFMK 45709 from Lan-Sak, Uthai Thani province, western Thailand).The English common name for I. borealis differs among the users and is variously called "Western Legless Skink" (Nabhitabhata et al. 2004;Nabhitabhata and Chan-ard 2005), "Northern Limbless Skink" (Das 2010;Tantipisanuh and Gale 2013) and "Lang's Isopachys" (Uetz and Hošek 2014).Considering the appearance of new specimens in scientific publications, only one additional specimen was referred to in the work of Kunya et al. (2011).This work reported an additional locality of I. roulei in Nakhon Ratchasima province (northeastern Thailand) based on a single additional specimen (THNHM 15362).Kunya et al. (2011: 90) also listed as part of their specimens examined one specimen of I. borealis (THNHM 15366, collected from Lansak district, Uthai Thani province by staff of Khao Nang Ram Wildlife Research Station, without collection date).This specimen was not cited elsewhere, and to date, other works about reptiles have not referred to additional specimens (e.g., Chan-ard et al. 1999;Nabhitabhata et al. 2004;Nabhitabhata and Chan-ard 2005;Das 2010;Chuaynkern and Chuaynkern 2012).Therefore, I. borealis is a rare, little-known species of skink.
We recently had the opportunity to examine a single specimen of a limbless lygosomine skink clearly belonging to the genus Isopachys.The specimen (Figures 1 and 2) was collected from Salak Phra Wildlife Sanctuary, Kanchanaburi province (western Thailand) by Watchara Chitchamnong on 6 July 2012.The skink was caught at the front of the Huay Sadong Protected Unit at the coordinates UTM zone 47 052277 E / 158287 N. Then the skink was fixed in 10% formalin and transferred to 70% alcohol.The specimen was catalogued (KKUC 00627) and is housed in the Khon Kaen University Vertebrate Collection (KKUC), Khon Kaen province, Thailand.
Identification of the specimen was based on taxonomic works (Smith 1935;Taylor 1963; Lang and Böhme 1990; Das

NOTES ON GEOGRAPHIC DISTRIBUTION
number of voucher specimens housed in various collections (e.g., Lönnberg 1916;Taylor 1963;Lang and Böhme 1990;Kunya et al. 2011).However, the distribution of I. anguinoides is also limited similar to those of the three other Isopachys (known from Chumphon, Phetchaburi, Prachuap Khiri Khan, Surat Thani provinces; Chuaynkern and Chuaynkern 2012).Kamsook et al. (2006) referred to the limbless skink Isopachys sp. from Phu Khiew Wildlife Sanctuary (Chaiyaphum province, northeastern Thailand) but its voucher specimen was not cited.Phu Khiew Wildlife Sanctuary is located nearby locality 8 (Figure 3) ca.70 km southwest of Nong Rua (=Nong Rua district, Khon Kaen province).The Isopachys sp. as referred to by Kamsook et al. (2006) is I. borealis or I. roulei because its locality falls within the distribution range of I. borealis or possibly I. roulei and its highest latitude falls in area of Nakhon Ratchasima province which is bordered in the south by Chaiyaphum province (Kunya et al. 2011).Furthermore, three other congeners are known to reside along the coast of the Gulf of Thailand and also in the western part of the country.
Although the additional discovery of Isopachys borealis in Kanchanaburi province as reported in this work brings the total known locality of specimens to nine (Figure 3) -Phadow (150 km south of Moulmein, Myanmar), Mae Sot (60 km west of Tak, Tak province, 2010).The specimen was assigned to Isopachys borealis as it fits the description of the species provided by Lang and Böhme (1990).In the description of I. borealis provided by Das (2010: 234), the nasals were noted as separated but in our specimen there was clearly broad contact as similar to the description of the species and head illustration of the holotype presented by Lang and Böhme (1990).Other morphological characters (Figures 1 and 2) are similar to I. borealis as follows: snout-vent length (SVL) 91.3 mm, tail length (TaiL) 31.7 mm; body elongated; limbless; snout flattened anteriorly; nasals in broad contact; frontonasal larger than frontal; supralabials 5; parietal eye absent; midbody scale rows 18; dorsum pinkish-fawn; forehead darker with T-shaped lighter frontal and frontonasal region; tail-tip rounded; 2 broad dark stripes from parietals, narrowing on dorsum and separated from each other by 2 entire scales and 2 half scales; on tail, dorsal line less distinct and fragmented; venter gray.However, the specimen from Kanchanaburi province shows little differentiation from the type series (in parenthesis): SVL 91.3 mm (77-177 mm), scale rows at neck 27 (23-28 rows), scale rows at mid body 21 (20-22 rows), scale rows at base of tail 20 (14-17 rows) and scales between parietal and vent 143 (140-152 scales).
The present work documents the first provincial record of Isopachys borealis for Kanchanaburi province, western Thailand, based on a single specimen (KKUC 00627).The locality known as "Huay Sadong Protected Unit, Salak Phra Wildlife Sanctuary" is located ca. 260 km south of other known localities of the species (Figure 1).
To date, the genus Isopachys contains four species: I. anguinoides (Boulenger, 1914), I. borealis Lang & Böhme, 1990, I. gyldenstolpei Lönnberg, 1916, and I. roulei (Angel, 1920).Among them, I. borealis, I. gyldenstolpei and I. roulei are extremely rare in the natural history collection.Their distribution is quite limited as well (Chuaynkern and Chuaynkern 2012): I. borealis is known from the provinces of Khon Kaen, Tak, Nakhon Sawan, Phetchabun and Uthai Thani provinces; I. gyldenstolpei from Kanchanaburi, Phetchaburi, Prachuap Khiri Khan, Uthai Thani; and I. roulei from Chon Buri and Nakhon Ratchasima provinces.Isopachys Anguinoides, in particular, is likely to have a greater  Thailand), Taling Sung (M Nakhon Sawan, Kamphaeng Phet province, Thailand), Dong Noi (Uthai Thani province, Thailand), Lan Sak (20 km west of Mueang Uthai Thani, Uthai Thani province, Thailand), Tap-Tan (Uthai Thani province, Thailand), Nam Len (30 km northeast of Phechabun, Phetchabun province, Thailand), Nong Rua (45 km west of Khon Kaen, Khon Kaen province, Thailand) and Salak Phra Wildlife Sanctuary, Kanchanaburi province) -there are still insufficient voucher specimens for a conclusive understanding of the species' geographic distribution.This scarcity of voucher specimens might be due to the members of this group inhabiting underground habitats (Smith 1935(Smith , 1937;;Taylor 1963;Heyer 1972;Lang and Böhme 1990;Das 2010).Moreover, the natural history of I. borealis is little known, and taxonomic workers have failed to find this skink in its natural habitat.This species' status has not yet been assessed for the IUCN Red List (IUCN 2013).For these reasons, I. borealis was assessed as Near Threatened in the Thailand Red Data (Nabhitabhata and Chanard 2005).Although the present work helps to fill a perceived distributional gap, our knowledge of I. borealis is still based only on morphology and a few distributional records.Therefore, further research on this species is needed before a more accurate assessment can be made.
We strongly believe that the geographical distribution of Isopachys borealis, and its congeners, are likely not fully known.Additional undiscovered populations probably exist in the gaps between the western, central and northeastern Thailand or populations may extend further to the north, or south and southeast, and into neighboring parts of Laos and Myanmar.This lack of definitive knowledge exists even though the herpetofauna of the Indochinese region has been given considerable attention during the last decade.Several new species and additional records were published by various authors (e.g., Teynié et al. 2004;Stuart and Emmett 2006), and our knowledge of these animals grows rapidly with regularly published checklists (Chan-ard et al. 1999;Nabhitabhata 2000;Nabhitabhata et al. 2004;Nabhitabhata and Chan-ard 2005;Chuaynkern and Chuaynkern 2012).However, further fieldwork likely will reveal additional records of I. borealis.