Description of holotype: A small pitviper with a subtriangular head that is very distinct from the neck, and a prehensile tail. Rostral overall trapezoidal, lower margin of rostral 2 × wider than upper margin, higher than wide, almost vertical along suture with first supralabial on right side, only slightly concave along supralabial suture on left side; dorsal margin of rostral rounded, projecting anteriorly, forming part of very sharply upturned canthus rostralis; nasal very large, undivided, dorsal margin of nasal projecting dorsally and laterally, forming major part of canthus rostralis; internal naris subelliptical, upper part turned slightly more anteriorly, twice as high as wide; external nare with posteroventral extension pointing toward supralacunalpostlacunal suture; posteroventral margin of external nare terminating at level of end of first half of nasal; loreals absent, nasal borders upper half (right side) to almost upper two-thirds (left side) of anterior margin of prelacunal; prefoveals 1 / 1, tiny, at junction of nasal, prelacunal and first supralabial; subfoveals 2 / 2, anterior one elongate, projecting towards anteroventral margin of orbit, bordering posteroventral corner of prelacunal, posterodorsal corner of second supralabial, anterodorsal corner of third supralabial, anteroventral half of postlacunal, and posterior subfoveal; posterior subfoveal drop-like in shape, wider posteriorly, directed towards lower margin of orbit, bordering posterior margin of anterior subfoveal, posterior part of first half of third supralabial, posteroventral half of postlacunal, anterior margin of sublacunal, lower margin of preocular; twothirds of posterior subfoveal extending beyond posterior corner of pit; prelacunal separated from second supralabial on both sides; postfoveals 1 / 1, tiny, anterior and lower portions partly covered by sublacunal and posterior subfoveal, excluded from orbit by posteroventral extension of supralacunal. Prelacunal moderately large, wider in lower part, higher than wide; on both sides bordered anteriorly in upper two-thirds by nasal, in lower one-third by first supralabial; anterior two-thirds of upper margin of prelacunal bordered by posterior half of third canthal; posterior one-third deep inside pit, covered by supralacunal; lower margin of prelacunal bordered by upper margin of second supralabial; lower posterior extension of prelacunal ending at level of upper posterior corner of second supralabial, bordered posteriorly by 1 / 1 subfoveals. Sublacunal small and short; shorter than lower margin of prelacunal, about as wide as height of posterior margin of nasal, slightly wider than lower margin of supralacunal; anterior end narrow, covered by lower posterior extension of prelacunal; extending in straight line up to contact with supralacunal; about 2 × wider posteriorly than anteriorly; lower anterior margin bordered by subfoveal that also contacts upper posterior part of second supralabial, upper anterior corner of third supralabial, lower / anterior postfoveal, and lower posterior corner of prelacunal; posteriorly, sublacunal bordering 2 / 2 postfoveals. Supralacunal large, anterodorsal projection bordering posterolateral margin of third canthal, remaining dorsal margin of supralacunal covered by fourth canthal which also forms upper preocular; posterior margin of supralacunal almost vertical, but rounded in lower posterior corner, here covering upper anterior end of small, rounded lower preocular; lower margin anteriorly bordering sublacunal, posteriorly bordering upper postfoveal; lower anterior margin forming posterodorsal border of pit, extending upwards in an angle of approximately 45 ° from above posterior one-third of sublacunal to start of posterolateral one-fourth of third canthal and posterior one-fourth of dorsal margin of prelacunal; lower anterior margin of supralacunal straight to slightly concave in upper part bordering pit. Preoculars 3 / 3, formed by entire posterior margin of small keeled scale that is completely fused to the posteriormost (fourth) canthal (upper preocular, bordering one-fourth of anterior margin of orbit), posterior margin of supralacunal (middle preocular, bordering half of anterior margin of orbit), and a small lower preocular; lower preocular touching the eye, forming only one-fourth of anterior margin of orbit; lower preocular located between supralacunal and subocular, separated from third supralabial by subocular and one small interoculabial. Suboculars 1 / 1, long and narrow; extending from before anterior margin of lower preocular to level of posteriormost point of orbit, about as wide anteriorly as posteriorly, smooth anteriorly, slightly rugose posteriorly, upper posterior margin covered by lower of two postoculars. Postoculars weakly keeled; upper postocular slightly larger, participating in orbit with about half of length of scale, about as much as lower postocular. Anterior end of left subocular in contact with central part of upper margin of third supralabial, posterior one-third of dorsal margin of third supralabial separated from subocular by one tiny triangular and one larger keeled interoculabial; right subocular separated from third supralabial; interoculabials 3 / 3, one row of scales between subocular and supralabials: one scale each between subocular and suture of third / fourth and fourth / fifth supralabial; 2 / 2 scales (in diagonal view) between posterior part of subocular and corner of sixth supralabials, the lowermost covered anteriorly by posterodorsal margin of fifth supralabial, posteriorly covering anterodorsal margin of sixth supralabial, both weakly keeled; 3 / 3 scales between posterior part of subocular and corner of seventh supralabials. Upper lip curved; highest parts located at rostro-mental contact and the corners of the mouth; lowest parts at suture of third / fourth supralabials, corresponding approximately to level of fourth / fifth infralabials. Supralabials 9 / 10; first supralabial extending up to one-third of height of prelacunal, separate from nasal; second supralabial about as large as first, separate from prelacunal; third supralabial largest, more than 2 × size of first supralabial, about 2 × wider than high; fourth supralabial second largest, about as high as wide; supralabials 5 – 9 / 5 – 10 much smaller than fourth, but larger than dorsally adjacent scales; ninth / tenth supralabials smallest. Internasals 1 / 1, small, about as wide as long; laterally covering anteromedian ends of first canthals. Canthals 4 / 4, first pair widest, second shortest, third and fourth elongate and narrow, smooth but some with uneven scale surface; first pair approximately 2 × longer than wide, entirely on top of head, bordered laterally by two intercanthals; second canthals ca. 1 ½ × longer than wide, bordered by three intercanthals; third canthals about 2 × longer than wide, bordered by two intercanthals; fourth canthals approximately 2 × longer than wide, bordered by two intercanthals and the supraocular; outer margins of third and fourth canthals turned to side of head; posteror tip of fourth canthal on both sides fused to tiny keeled scale adjacent to anterolateral margin of supraoculars. Canthus rostralis sharply pronounced, projecting anteriorly and anterolaterally; nasals, first and second canthals and internasals contributing more to canthus rostralis than third and fourth canthals. Anterior and lateral intercanthals only weakly keeled, central intercanthals more distinctly keeled, mostly narrower than internasals but often longer; three intercanthals between first pair of canthals immediately posterior to internasals, the middle one directly posterior to the internasal suture being very small; increasing posteriorly to 5, 6, 7, 8 and 9 – 10 intercanthals, the latter between the fourth canthals. Supraoculars small, elongate and narrow, with uneven scale surface and poorly defined margins due to obvious fusion with at least two adjacent scales each, on either side with 1 – 2 indistinct keels; supraoculars about 1 ½ – 2 × longer and 2 × wider than fourth canthals; bordered by 8 / 8 scales including the fourth canthals with posteriorly fused scale and postoculars. Intersupraoculars keeled, minimum number 9 (between anterior ends of supraoculars), maximum number 13 (between posterior ends), 11 between middle of supraoculars. Posterior head scales weakly to strongly keeled; approximately 32 interrictals. Scales on lower head (especially mental, chinshields, also anterior infralabials and supralabials) with numerous tiny tubercular structures (presumably mechanoreceptors). Mental large, anterior margin of convex appearance, slightly concave on both sides, wider than long; bordered by first infralabials; posterior tip of mental separating first infralabials, extending between anterior end of chinshield suture. Infralabials 9 / 10; first infralabials 2 × higher than wide in upper part, in contact with mental, second infralabials, and chinshields; second infralabials small, rectangular, wider than high; on left side, third infralabial wider and ca. 1 ½ × higher than second infralabials; on right side, third infralabial small, 2 × higher than wide; infralabials 4 / 5 + 6 largest, infralabials 5 – 9 / 7 – 10 of similar size and shape, gradually becoming smaller posteriorly; on left side, ninth infralabial smallest (about ½ × smaller than second infralabial); on right side, tenth infralabial second smallest, being slightly larger than third infralabial. One pair of chinshields, wide, with pointed posterior extension left and right of distinct mental groove, about 2 × longer than wide at longest part; bordered by mental, infralabials 1 – 2, two sublabials, and first gular; chinshields followed by seven pairs of smooth to very slightly keeled gulars, the anterior of which are wider than long, followed posteriorly by one preventral that is mostly covered by laterally adjacent scales; 6 – 7 rows of sublabials between last infralabial and posteriormost gular; 146 ventrals; anal plate undivided; 52 subcaudals, all divided, plus a terminal scale equal in length to two terminal subcaudals; dorsal body scales arranged in 21 / 21 / 17 rows, only slightly keeled, most keels only on posterior half of scale, extending to terminus of scale; paraventrals smooth over most of body, slightly wider than adjacent dorsals; dorsal scales on tail and parasubcaudals without keels. Measurements of holotype (in millimeters): SVL 350, TL 66, EP 1.2, EN 5.8, ED 3.5, HL 20.9, RH 2.69, RW 2.63. Coloration of holotype (in preservative; figs. 1 – 5, 6 A, 7 A): Top of head with ornate head pattern composed of brown, green and cream elements; in dorsal view, outer margins of internasals and first canthals greenish cream, central portions as well as anteromedian parts of first intercanthals brown; posterior part of resulting brown spot on right side connected to larger brown spot centered in anterior canthal region, covering an area of approximately ten intercanthals; two brown spots of similar size and shape in posterior intercanthal region, left one separate from anterior intercanthal spot and left supraocular but with small V-shaped central extension, right one broadly fused to anterior intercanthal spot and just contacting anteromedian margin of right supraocular; two smaller, irregularly shaped brown spots in anterior intersupraocular region; supraoculars centrally with brown area that is continuous (left) or near continuous (right) to large L-shaped (left) and inversely L-shaped (right) brown blotch; posteromedian extensions of these latter blotches pointing toward each other but not in contact in occipital region, thereby framing a fronto-parietal area that contains a roughly trapezoidal brown mark with central green spot; another brown spot involving about ten scales posterior to where short legs of L-shaped blotches point toward each other; right (inversely) L-shaped blotch posteriorly fused to large brown interrictal mark that is concave anteromedially and posterolaterally, convex anterolaterally, has a posteromedian extension pointing toward the neck, and at its outer posterior margins connects to brown pattern elements on the posterior sides of the head; brown spots on top of head in various parts with indistinct darker to blackish outer margins, in addition to more distinct, narrow cream to greenish cream borders that set off the brown head pattern from much of the intervening light green (top of snout) to dark green (posterior head) areas. Rostral pale greenish yellow with brown upper and lower margins and small brownish central suffusion; anteroventral corner of nasal pale greenish yellow up to anteroventral margin of naris, rest of nasal brown; first pair of supralabials brown along sutures with rostral and brown part of nasal and prelacunal, pale greenish yellow elsewhere; second supralabial pale yellow with greenish hue centered near posterodorsal corner, and irregularly dark-edged brown spot in lower central part of scale; lower part of prelacunal cream, upper part greenish, finely dusted with brown; posterior two canthals with cream inner and brown outer margins; all scales bordering anterior orbit, including entire supralacunal, brown mixed with green pigment; posterior half of sublacunal brown mixed with green, anterior half cream; subfoveal cream; postfoveals brown mixed with green; third supralabial with wide central brown area extending down from brown preocular area, set off from cream anterior and posterior margins of third supralabial by narrow dark brown to black margins; anteriormost tip of subocular brown (part of brown preocular area), then cream up to about level of center of eye, and brown posteriorly; lower postocular brown, upper postocular cream with brown lower corner; from fourth supralabial posteriorly, ground color of supralabials and margins of adjacent scales pale yellowish green; anterior margin of fourth supralabial and anterior one-third of interoculabial between third and fourth supralabial and subocular cream; fourth supralabial with dorsally rounded brown spot on lower central margin; fifth to eighth supralabials with brown or black lower central margins; color of eye golden, with extensive black pigment anterior and posterior to vertically elliptical pupil, indicative of a continuation of the brown pre-and postocular stripe; wide brown postocular stripe extending from posterior orbit to beyond angle of jaw, covering 3 – 4.5 scales in width, upper and lower margin delimited by black pigment only on a few scales; upper margin of postocular stripe bordered by narrow cream line extending from upper postocular to beyond angle of jaw. Mental and first infralabials greenish yellow, with indistinct brown spots on both upper mental-infralabial sutures and lower (posterior) end of mental; ground color of infralabials from cream and greenish yellow anteriorly to pale yellowish green posteriorly, with variable degrees of brown dusting and spots; posterior part of second infralabial dusted with brown; third infralabial with poorly defined small brown streak in upper central part; fourth infralabial with brown spot in lower anterior corner and narrow diagonal extension to upper posterior corner; brown posterior margin of fifth and brown anterior margin of seventh supralabial forming dark-edged light brown infralabial spot together with brown-dusted sixth infralabial; upper posterior corner of seventh and upper anterior corner of eighth infralabial also with brown spot; posterior half of posteriormost supralabial and posterior one-third of posteriormost infralabial forming part of dark brown margin of postocular stripe; ground color of scales on lower side of head cream to yellowish green; chinshields each with small black central spot and posterolateral black-edged brown spot that continues posteriorly as a poorly defined brown pattern element on adjacent scales; numerous gulars and other scales with small brown or black spots or streaks or dusted with brown or black pigment. Dorsal body pattern consisting of 35 brick-red to brown rings that are 2.5 – 4 dorsal scales long midvertebrally; ventrally, most of these rings are slightly directed toward the head; several rings laterally divided, juxtaposed, or incomplete dorsally or laterally (ring 1 split on right side; 2 split on left; 2 + 3 dorsally almost fused, 3 on right side separated from ventral part; 4 split on left; 5 split on right; 7 split on left; 8 incomplete on right; 13 + 30 dorsally almost interrupted, juxtaposed; 15 ventrally incomplete; 31 + 33 laterally divided on both sides; 34 with anterior dorsal extension pointing toward 33; 35 present only on right side, dorsally pointing toward 34); brown rings about as wide as or wider than interspaces; anterodorsal part of light interspaces of body pattern containing wide green bands; posterodorsal part of light interspaces with narrow cream bands; laterally, green color of light interspaces gradually fading towards venter; ventrolaterally, interspaces mostly cream to white, on outer edges of ventrals with small dark (brown or black-edged brown) spots of variable number (usually 1 – 3), size, and shape; brown rings across belly connected midventrally to form midventral stripe; midventral stripe almost continuous along body, only four times interrupted at levels of first to sixth brown rings; midventral stripe about as wide as ventral part of brown rings, approximately as wide as 1 – 3 ventrals, with lateral extensions; midventral stripe and ventral part of brown rings tan to light brown, mostly blackedged; posterior margins of most ventrals at midventral stripe darker brown or black; ventral ground color cream to light tan; base of tail with ten distinct brown rings; rings 2 + 3 on tail dorsally fused; rings 4 + 5 in contact dorsally; all other rings on tail separated by cream interspaces; green color on tail confined to dorsal parts of basal light interspaces; tip of tail light reddish brown with no rings or bands. Variation: The number of ventral scales varies between 139 and 146 (males: 146; females: 139 – 140 ventrals); the number of subcaudals ranges from 49 – 52 (males: 50 – 52; females: 49 - 51), all of which are divided. Supralabials 9 – 11 (males: 9 – 10; females: 10 – 11); interoculabials 3 – 4 (males: 3; females: 3 – 4); postoculars 2 – 3 (males: 2; females: 2 – 3), of which the lower 1 – 2 may be fused to the subocular; infralabials 9 – 11 (males: 9 – 10; females: 10 – 11), the first pair of which may or may not be in contact posterior to the mental; 4 – 7 gulars (males: 4 – 7; females: 7) between chinshield and first (pre-) ventral, arranged in pairs or (posteriorly) in rows of three; preventrals 0 – 2 (males: 1 – 2; females: 0 – 2); intersupraoculars 9 – 13 (males: 9 – 10; females: 10 – 13); scales bordering intersupraoculars 8 – 9 (males: 8 – 9; females: 8 – 9); canthals 3 – 4 (males: 3 – 4; females: 3 – 4); intercanthals 3 – 7 (males: 3 – 6; females: 5 – 7) between first canthals, 9 – 12 (males: 9 – 11; females: 11 – 12) between posterior canthals; internasals 2, in contact, or separated by scale of approximately equal size, or anteromedian part of each internasal divided to form two separate scales; prefoveals 0 – 4 (males: 0 – 1; females: 2 – 4); dorsal scale rows 25 / 21 / 19 in males, 23 – 25 / 25 / 19 in females. Variation in color pattern includes about 30 – 42 dark brick-red to brown rings or bands on the body (males: 31 – 35; adult females: 30 – 38; juvenile female: ca. 40 – 42) which may be disintegrated, incomplete or juxtaposed vertebrally or laterally, interrupted laterally on one or both sides, and cover 2 – 5 dorsal scales in length midvertebrally; brown rings or bands bordered especially anteriorly, but sometimes also posteriorly, by narrow cream to white (fig. 11 A + B) areas, or without distinct light borders (fig. 10 A); some with narrow black borders along brown rings or bands (e. g., fig. 10 A); 7 – 11 distinct brown rings or bands on basal part of tail (males: 10 – 11; adult females: 7 – 8; juvenile female: 11); light interspaces between brown rings or bands covering 1 – 3 dorsal scales in length midvertebrally; light interspaces very narrow in the juvenile specimen (NMW 27963: 2), cream to tan after more than 200 years in preservative (possibly green in life); light interspaces of the other specimens dorsally with wider green anterior part that may be nearly as wide as the brown rings, and with or without narrow cream to white posterior part that borders the following brown ring; laterally, green color of light interspaces gradually fading towards venter; ventrolaterally, interspaces mostly cream to white, on outer edges of ventrals with small dark (brown or black-edged brown) spots of variable number (usually 1 – 3), size, and shape that may be connected to a brown midventral stripe; dorsal scales of green areas of many light interspaces also with brown, black-edged brown, or black spots and streaks that may laterally extend up to the midvertebral region; green color on tail confined to dorsal parts of basal light interspaces; ventral ground color light tan to cream or dirty white; brown rings on venter connected to midventral stripe that may be incomplete and juxtaposed on anterior body (fig. 3), or disintegrated in chessboard-like pattern of dark grey mottling especially on lateral parts of ventrals in the absence of a distinct midventral stripe (fig. 10 B); midventral stripe about as wide as ventral part of brown rings, approximately as wide as 1 – 3 ventrals, often with multiple lateral extensions; midventral stripe and ventral part of brown rings tan to light brown, mostly black-edged; posterior margins of ventrals in midventral stripe often also darker brown or black.
