A large and unusually colored new snake species of the genus Tantilla (Squamata; Colubridae) from the Peruvian Andes

Tantilla tjiasmantoi sp. nov.

urn:lsid:zoobank.org:act:15B70DA0-55D5-47D9-8383-453869F3B530

Holotype

CORBIDI 7726 from Pías, Province Pataz, Department of La Libertad, Peru (07°53^′56.6^′′S, 77°34^′43.8^′′W, 1,726 m a.s.l), collected by E. Hoyos Granda, A. Beraún and C. Koch on 15 January 2010.

Paratype

ZFMK 95238, from Santa Rosa/El Tingo (Marcamachay), Province Cajabamba, Department of La Libertad, Peru (07°21^′59.3^′′S, 77°53^′53.0^′′W, 1,154 m a.s.l.), collected by M. Palacios Panta and C. Koch on 13 October 2010.

Diagnosis and definition

This comparatively large Tantilla is distinguished from its congeners by the following combination of characters: (1) maximum known SVL of 513 mm and total length of 638 mm; (2) 179–182 ventrals; (3) 57–65 paired subcaudals; (4) 7 supralabials; (5) eyes small, not visible from below, with round pupils; (6) dorsals smooth, without keels or apical pits, rhomboid, in 15 rows throughout the body; (7) loreals absent; (8) suboculars absent; (9) 2 postoculars; (10) 1 + 1 temporals; (11) cloacal plate divided; (12) hypapophyses absent on posterior vertebrae; (13) hemipenes single; (14) body with dark bands that are not closed on ventral side; (15) conspicuous sexual dimorphism present.

With a maximum known total length of 638 mm Tantilla tjiasmantoi sp. nov. is among the largest species in the genus, only T. shawi, T. impensa, and T. semicincta reach similar or even larger total length. It can further be easily distinguished from all congeners except for T. shawi, T. semicincta, and T. supracincta by having a transversely-banded color pattern on the dorsal part of the body. The higher number of subcaudals (57–65) differentiates the new species from T. shawi (48–50) and the higher number of ventrals (179–182) further distinguishes it from T. impensa (162–172), T. semicincta (161–176) and T. supracincta (138–151), as well as from the Peruvian species T. capistrata (130–156) and T. melancocephala (125–177). From the other species occurring in mainland South America, it can further be distinguished by a higher number of ventrals as compared to T. alticola (128–145), T. andinista (157), T. boipiranga (156–167), T. miyatai (165–172), T. nigra (137), T. petersi (172), T. insulamontana (144–157), T. reticulata (158–173).

Description of holotype

An adult female with a SVL of 513 mm; TL 125 mm; HL 16.3 mm; HW 12.2 mm; HH 6.1 mm; TL/Total Length 0.2; SVL/HL 31.5; SVL/HW 42.1; SVL/HH 84.1; HW/HL 0.75; HH/HL 2.7; ED 1.5 mm; HL/ED 10.9; HW/ED 8.1; MBD 11.5 mm; SVL/MBD 44.6; DSN 1.5 mm; DNE 3 mm; MTD 2.9 mm.

Body robust, tail long, body and tail round in cross-section; dorsal scales in 15-15-15-rows, without reduction, rhomboid, smooth, lacking keels or apical pits; 182 ventrals; tail distinctly smaller in diameter than the body, long and tapering, tail spine pointed; 57 paired subcaudals; cloacal plate divided.

Head (Fig. 3) distinct from the body and depressed, laterally broadened behind the eyes. Rostral visible in dorsal view, slightly triangular with dorsal termination subacute, about 1.9 times wider than high. Snout rounded in dorsal view. Two internasals, subequal, about twice as broad as long, laterally in contact with anterior and posterior nasals. Prefrontals large, 1.2 times broader than long, laterally contacting postnasal, second supralabial and preocular. Frontal slightly hexagonal with dorsal termination acute, about 1.2 times longer than wide, laterally in contact with supraoculars, laterodorsally in contact with parietals. Supraoculars about 2.1 times wider than high. Parietals large, 1.6 times longer than wide, median suture about as long as frontal length. Nostrils located in posterior portion of anterior nasals. Anterior nasals about as high as broad, contacting rostral, internasal, postnasal, and first supralabial. Posterior nasals about 1.8 times longer than high, contacting anterior nasal, internasal, prefrontal, and first and second supralabial. No loreal. Eyes small with round pupils, partly visible in dorsal view, surrounded by one preocular, one supraocular, two postoculars, and third and fourth supralabial. No suboculars. Preoculars almost squarish. Superior postoculars, about 1.5 times longer than high; lower postoculars slightly pentagonal to almost circular. Supralabials 7/7, increasing in size posteriard, last one very large, about three times higher and 2.2 times broader than first supralabial, second contacting postnasal and preocular, third contacting prefrontal and eye, fourth contacting eye and lower postocular, fifth contacting lower postocular and anterior temporal, sixth contacting anterior temporal, seventh contacting anterior and posterior temporals, and first scale of dorsolateral and lateral body scale row, respectively. 1 +1 temporals, almost rectangular, separating supralabials 5–7 from parietals, anterior temporal about 2.5 times longer than high on both sides, 1.3 times longer than posterior one on left side and almost twice as long as posterior one on right side of head, posterior temporal 1.8 times longer than high on left side and about 1.1 times longer than high on right side of head. Mental subrhombical, 1.4 times broader than long, separated from chinshields by first pair of infralabials, which contact each other along the ventral midline. Infralabials 7/7, fourth largest, second smallest, first to fourth contacting anterior pair of chinshields; fourth infralabial contacting posterior chinshield and first gular scale. Two pairs of almost rectangular chinshields; anterior chinshields about 1.7 times longer than wide and 1.3 times longer than posterior chinshields; posterior chinshields about 2.2 times longer than wide, laterally contacting fourth infralabial, dorsally separated from the ventrals by four gular scales.

Trunk vertebrae 185; hypapophyses present on anterior 1/5 of trunk vertebrae, absent on posterior vertebrae; caudal vertebrae 56 (Fig. 4).

Coloration

In live, the dorsal ground color of head, body and tail is orange-yellowish, slightly paler laterally, most scales on body and tail with reddish-brown outlines; there are about 27 blackish dorsal crossbars on the body that are four to seven scales in length and are stretched across all dorsal scale rows except the most lateral row, slightly longer than ground color interspaces, fused in some parts of the body to form a zigzag band, slightly mottled in some parts with yellow. There are 12 dark tail blotches, reaching to subcaudals on both sides, fused in median part of the tail along the midline to form a zigzag band. Head with a large dark dorsal t-shirt-shaped blotch covering frontal, supraoculars, most of parietals except for the most posterior parts, and posterior part of prefrontals, the dark blotch is laterally extended at eye level, covering orbit, preocular, third supralabial, and adjacent parts of second and fourth supralabials, respectively. Infralabials, rostral and mental yellowish, except for blackish region surrounding the lingual groove. The ventral scales of head and body and subcaudal scales are cream-colored with dark dotted outlines in some parts. The coloration of the tongue is black to grayish-black (Fig. 5).

In preservative, the dorsal pattern on body and tail of a light ground color with dark crossbands remains unchanged, likewise the dark coloration of the head; the orange-yellowish dorsal ground color changed to cream and the darker outlines of most dorsal scales disappeared; the ventral coloration changed to grayish-white in some parts (Fig. 5). The coloration of the tongue changed to gray.

Variation

The single paratype is a small male with a conspicuous sexual dimorphism in body size and ventral coloration compared to the holotype. As the hemipenes ornamentation is as detailed as in other adult specimens of the genus Tantilla we assumed it to be already sexually mature. Intraspecific variation in scale counts and measurements is shown in Table 2. The paratype further differs from the holotype in the following characters: SVL/HL 24.4; HW/HL 0.58; ED 1.1 mm; HL/ED 7.4; HW/ED 4.3; MBD 3.5 mm; SVL/MBD 56.6; DSN 1.0 mm; DNE 1.3 mm; MTD 1.3 mm. On the right side this specimen has only 6 infralabials, of which the third one is the largest.

The dorsal ground coloration of the paratype (Fig. 5) in live is bright yellow and there are 35 blackish dorsal crossbars on the body and 16 dark tail blotches, some of the latter are fused to form a zigzag band, the black parts are usually not mottled with yellow. The t-shirt-shaped dark pattern on the dorsal surface of the head is also present in this specimen, but there is a dark vertical line on the left side of the head covering whole sixth and adjacent parts of seventh supralabial. On left side of the head posterior part of second infralabial and infralabials three to five are dark, on right side of head the posterior part of third infralabial and the infralabials four to six are dark. The ventral coloration differs from the holotype as the dark dorsal coloration of the paratype continues on the ventral scales, and thus sometimes forming complete rings around the body or creating a checkerboard pattern on the ventral surface of black and cream squares. There are 179 trunk vertebrae and 70 caudal vertebrae (Fig. 4).

Cranial osteology

The snout is terminated by a small, single, toothless, median premaxilla. The triangular-shaped dorsal process of the premaxilla is not contacting the anterior portion of the two nasals. The paired nasals are slightly convex and oval-shaped in dorsal view, medially in contact and separate anteriorly to from an interspace. Their posterior edges are in contact with the anterior inner edges of the frontals. The paired frontals are dorsally flat, subrectangular, longer than broad, slightly larger than the nasals, and in close medial contact. The posterolateral edge of each frontal forms a supraorbital ridge which is perforated with two supraorbital foramina. The lateral surface of the frontal forms a major portion of the mesial wall of the orbit. The prefrontal is loosely attached to the anterolateral edge of the frontal. In lateral view, the prefrontal is anteriorly contacting the posterior edge of the nasal and the septomaxilla, and the ventral border is contacting the dorsal surface of the maxilla. The frontals articulate posteriorly with the fused parietals. In dorsal view, the parietal is flat, oval-shaped except for the more or less straight anterior border along the suture with the frontals. It is the largest of the cranial elements and like the frontals, extends laterally far down, reaching ventrally to the basisphenoid. The parietal forms the posterior portion of each orbit. Its posterolateral borders suture with the prootics and its posterior border sutures with the supraoccipital. The postorbitals are narrow, elongate, flattened, slightly curved bones, larger than the prefrontals. They articulate with the anterolateral surface of the parietal and form the dorsoposterior boundary of each orbit. The single supraoccipital is flat, subpentagonal, and broader than long. Laterally it unites with the prootics and posteriorly with the exoccipitals. The paired prootics are largely separated by the broad supraoccipital. Each prootic is subtrapezoidal in dorsal view and is posteriorly bordered by the exoccipital. Laterally it extends far down, reaching ventrally the basisphenoid and the basioccipital. Each prootic has two large foramen of which the anterior one is anteriorly not enclosed by bone. The posterior foramen is larger than the anterior one. Other smaller foramina pierce each prootic. Posterodorsally each prootic is fused with the elongate, spine-like supratemporal, which connects the posterolateral dorsal part of the skull with the proximal end of the quadrate. Both supratemprals are almost parallel to each other, converging only slightly posteriard. The exoccipitals are dorsally flat, form the posterolateral walls of the braincase and are joined together by a mid-dorsal suture. Ventrally they are resting upon the basioccipital. The basioccipital is pentagonal-shaped and joined anteroventrally with the basisphenoid along a straight transverse suture. The basisphenoid is applied anteriorly without a suture to the narrow, elongate parasphenoid, forming a single bone, which extends anteriorly into the rostrum area and becomes the floor of the orbit. Each maxilla is a curved bar with a small horizontal dorsoposteriorly-pointing process, about midway on the mesial border, that articulates with the ventral surface of the prefrontal. Anterodorsally articulates with the posteroventral surface of the septomaxilla. The posterior end of the maxilla is broadened and received by the flattened, pincers-shaped ectopterygoid, which connects it to the pterygoid. Each maxilla bears sockets for about 18 prediastemal, slightly recurved teeth, followed by two slightly enlarged, ungrooved fangs. The ectopterygoid do not bear teeth. The narrow palatine bears 13 or 14 teeth. The posterior end of each palatine articulates with the anterior end of the pterygoid. At about the height of the third and fourth tooth each palatine possesses a broad, horizontally flattened, lateral maxillary process. At about the height of the sixth to eighth tooth each palatine possesses a similar but median choanal process with the apex directed anteriorly. The pterygoid is a slightly curved, flattened bar with about 17 teeth along the medial border. The subtriangular quadrate articulates with the lateral border of the supratemporal and its distal surface articulates with the mandibular condyle. The mandible is composed of two jaw bones. The anterolateral portion of the jaw is formed by the dentary, which contains a row of about 22, slightly recurved teeth. The longer proximal part of each jaw is without teeth (Fig. 6).

Hemipenial morphology

The hemipenes are unilobed, unicalyculate and noncapitate with a single sulcus spermaticus. The apical part is mostly uniformly spinulate. The hemipenial body is more or less uniformly ornamented with long and thin spines, which increase in size towards the base (Fig. 7).

Etymology

The species is dedicated to Wewin Tjiasmanto (Indonesia) in recognition of his support of nature conservation and taxonomic research through the BIOPAT initiative.

Distribution and natural history

This species is so far known from the southern portion of the seasonally dry forest along the Marañón River and its tributaries, from near Santa Rosa de Marcamachay at the Río Crisnejas, Province Cajabamba, and from near Laguna de Pías, Province Pataz, both Department of La Libertad, at elevations of 1,154 m and 1,726 m a.s.l., respectively (Figs. 8 & 9). The female CORBIDI 7726 was detected on 7th of January 2010 at 12.30 pm resting on a stone. The male ZFMK 95238 was detected on 12th of October 2010 at 8.15 pm on pebbly-clayey ground. Air temperature when animals were sighted was 33.3 °C and 28.1 °C, respectively.