A new species of Mud Snake (Serpentes, Homalopsidae, Gyiophis Murphy & Voris, 2014) from Myanmar with a first molecular phylogenetic assessment of the genus Author Quah, Evan S. H. Author Grismer, L. Lee Author Wood, Perry L. Author Thura, Myint Kyaw Author Zin, Thaw Author Kyaw, Htet Author Lwin, Ngwe Author Grismer, Marta S. Author Murdoch, Matthew L. text Zootaxa 2017 4238 4 571 582 journal article 36329 10.11646/zootaxa.4238.4.5 e17e2c89-bf5a-4747-8af1-3ab31d497bd1 1175-5326 375507 8070D6DA-F5DB-4612-A768-2A61D56A2B70 Gyiophis salweenensis sp. nov. Salween River Basin Mud Snake Figs. 2–4 . Holotype . Adult female ( LSUHC 12960 ) collected on 8 October 2016 by Myint Kyaw Thura , Thaw Zin , Evan S.H. Quah , L. Lee Grismer , Perry L. Wood, Jr. , Marta S. Grismer , Matthew L. Murdoch and Htet Kyaw from close to Sanpel Cave, Mawlamyine , Mon State , Myanmar ( N16°22.427 , E97°46.388 ; 44 m in elevation). Diagnosis. Gyiophis salweenensis sp. nov. is separated from all congeners by having a unique combination of the following characters: a narrow rostral scale; the first three dorsal scale rows square; 129 (female) ventral scales; 30/29 (female) paired subcaudals; a divided cloacal plate; eight or nine supralabials; 10 infralabials; a maximum total length of 416 mm ; relative tail length ratio of 0.13; a ventral patterning lacking a central spot on each ventral scale; the presence of a faint stripe on the lower, dorsal scale rows; and four rows of dark spots on the dorsum ( Table 1 ). TABLE 1. Comparison of the scalation and colour pattern in G. maculosa , G. vorisi and G. salweenensis sp. nov. *data obtained from Murphy 2007b, – no data available.

Characteristics Scale rows on neck (ASR)	Gyiophis maculosa * (N=1) 25	Gyiophis vorisi * (N=11) 26–28	Gyiophis salweenensis sp. nov. (N=1) 26
Scale rows at mid-body (MSR) Scale rows near vent (PSR) Scale shape in first 3 rows	25 22 Ovate	25 21–23 Square	25 20 Square
Supralabials Ventral scales in males Ventral scales in females	8 - 122	8 147– 152 142–148	9/8 - 129
Subcaudal scales in males Subcaudal scales in females Central spot on each ventral	- 32/31 Present	51–58 41–53 None	- 30/29 None
Stripe on dorsal rows 2–4 Number of rows of spots on the dorsum Width of rostral scale	Absent 5–6 Narrow	Present 3 Broad	Present (Faint) 4 Narrow

Description of holotype ( Figs. 3–4 ). Head depressed, distinct from neck; snout short and rounded, rostrum tapers downwards; rostral scale pentagonal, nearly as broad as tall, visible from above; eye moderate in size, pupils rounded; nasals semi-divided with nasal groove contacting first supralabial, nare in center (on left side of snout is a small, aberrant, triangular scale positioned between rostral, nasal and first supralabial); internasal small, quadrangular, not in contact with loreal; loreal 1/1, quadrangular, contacting first three supralabials on right side and supralabials 1, 2 and 4 on left side; preocular 1/1; supraocular 1/1; postoculars 2/2; prefrontals 2, in broad contact with each other, frontal, internasal, loreals, preoculars, supraoculars, and posterior tip of nasals; frontal pentagonal, 1.4 times longer than supraocular; parietals elongate; temporal scale formula 1 + 2 + 3; supralabials 9/ 8, largest supralabial 7/6, smallest 3/8, supralabial entering orbit 5/4 (on left side of head there is fragmentation of supralabial scales with third supralabial being small and sandwiched beneath second and fourth supralabials ( Fig. 4 b); infralabials 10/10, seventh elongate, first four in contact with anterior chin shield; anterior pair of chin shields largest and rounded, second pair small; 26 ASR, 25 MSR, 20 PSR; scales of first three rows of dorsal scales square; 129 ventrals; cloacal plate divided; subcaudal scales 30/29. Body short, somewhat stocky; tail short; SVL 364 mm ; TaL 52mm ; TL 416mm . There is a puncture wound on the right side of the dorsum at the position of ventral 63. Colouration in life ( Figs. 2–4 ). The colour of each ventral and subcaudal scale is uniform cream with dark edging on the anterior right and left corners of each scale. These markings merge with the dark spot on the anterior half of each scale of the first dorsal scale row and some on the second row of dorsal scales to form a zig-zag stripe along the dorsoventral edge that runs the length of the body and tail. There are no central spots on the ventral scales except for ventrals 21, 54 and 55 that are extensions of the dark edgings of the corners of the scales. The chin and throat are cream and the infralabials, chin shields, and scales on the throat are edged in dark-grey. The posterior portion of dorsal scale rows one, two, three, and four form a faint cream stripe that is most prominent on the anterior portion on the body near the jaw and neck. The ground colour of the top of the head and the dorsum is greyish-brown. On dorsal scale rows 5–7 there are a series of large black spots 3–7 scales wide along the flanks and the anterior portion of the body near the neck. Some of these spots merge to form an irregularly shaped stripe. On the back are two rows of smaller black spots approximately 2–4 scales in width and usually on dorsal scale rows 11–14 and rows 15–17. Some single, darker scales are interspersed along the body on dorsal scale rows nine or 10. The tail is greyish brown with black spots. The head is speckled with small dark-grey spots with some larger spots; one on the frontal; another beneath the eye on the lower postocular and supralabials 4/5 and six. There is a broad dark-coloured streak across the anterior temporal, lower middle temporal, and the seventh and eighth supralabials; one at the corner of the jaw; and another two-scale wide streak on the crown from the posterior tip of the parietals extending posteriorly the length of five dorsal scales. The supralabials are cream and edged in dark-grey. Distribution ( Fig. 2 ). Gyiophis salweenensis sp. nov. is only known from the type locality near Sanpel Cave, Mon State, Myanmar . It is expected to be wider ranging throughout the Salween River Basin and found wherever appropriate habitat occurs. Natural history ( Fig. 5 ). The holotype was found at approximately 1930 hours crossing a narrow dirt road between flooded fields that we presume to be its natural habitat. The weather was overcast and it rained later that night. Many other species of homalopsids are semiaquatic and commonly found in streams, rivers, ponds, and flooded rice fields ( Murphy 2007a ; Stuebing et al . 2014 ). Gyiophis salweenensis sp. nov. is expected to share a similar life history and the valvular nostrils located dorsally on the snout indicate this species probably spends a large part of its life in the water. Homalopsid snakes such as Enhydris enhydris , Homalopsis buccata ( Linnaeus, 1758 ) and Hypsiscopus plumbea have been observed crawling on land and crossing roads during wet weather ( Voris & Karns 1996 ; Lim & D’Rozario 2009; EQSH personal obs.) and the holotype of G. salweenensis sp. nov. could have been dispersing to a new area as well. The holotype also had a puncture wound on its back which might have come from an encounter with a predator such as a heron. Etymology. The specific epithet salweenensis is in reference to area where the holotype was found which is close to the vicinity of the Salween River near the city of Mawlamyine. The suffix ensis is a Latin derivation meaning “from” or “inhabiting.” It renders the specific epithet an adjective that must be in grammatical accord with the gender of Gyiophis . Comparison. Gyiophis salweenensis sp. nov. is distinguishable from G. maculosa by the shape of the dorsal scales of first three rows (square vs. ovate), the ventral scale pattern (absence of a central spot on each ventral scale vs. its presence), and a stripe running through the scales of the lower dorsal scale row (faint one vs. absent). It is further distinguished from G. vorisi by its lower number of ventrals (129 vs. 142–152), lower number of subcaudals (30/29 vs. 41–58), shape of the rostral scale (narrow vs. broad), and the number of rows of spots on the dorsum (four vs. three) ( Table 1 ). It differs from the other species of homalopsids found in Myanmar by unique suite of characters presented in the key below.