Elaphe xiphodonta, Qi & Shi & Ma & Gao & Bu & Grismer & Li & Wang, 2021

Qi, Shuo, Shi, Jing-Song, Ma, Yan-Bo, Gao, Yi-Fei, Bu, Shu-Hai, Grismer, L. Lee, Li, Pi-Peng & Wang, Ying-Yong, 2021, A sheep in wolf's clothing: Elaphe xiphodonta sp. nov. (Squamata, Colubridae) and its possible mimicry to Protobothrops jerdonii, ZooKeys 1048, pp. 23-47 : 23

Elaphe xiphodonta sp. nov.

Material examined.

Holotype. SYS r002534, adult female (Figs 1 , 2 , 3A ), collected by Yan-Bo Ma, Yi-Fei Gao on 4 September 2020 from Chengguan Town (33.58°N, 108.46°E (DD); ca 1731 m a.s.l.), Ningshaan County, Shaanxi Province, China . Paratypes. IVPP OV 2721, juvenile female (Fig. 3C ), collected by Jing-Song Shi on 7 September 2020 from Chengguan Town (33.56°N, 108.50°E (DD); ca 1751 m a.s.l.), Ningshaan County, Shaanxi Province, China (Fig. 4 ) .

Etymology. The specific epithet " xiphodonta " of the new species comes from the Ancient Greek "ξίφοσ (ksίfos, refer to ‘knife’ or ‘blade’)” and "δοντι ( dónti, refer to ‘tooth’)”, meaning "blade-shaped teeth", indicating that the new species has unique blade-shaped MT and DT (Figs 5 , 6 ), which differs from the inconspicuous dental specializations (all teeth are cone-shaped) in its congeners. We suggest the Chinese formal name as “秦皇锦蛇” ( Qín Huáng Jǐn Shé), which derived from Qin Shi Huang (personal name: Ying Zheng or Zhao Zheng; 259 BC-210 BC), the founder of the Qin dynasty and the first emperor of unified China, whose territory including the distribution range of Elaphe xiphodonta sp. nov. The English name is suggested as "Qin Emperor Rat Snake" or "Blade-teethed Rat Snake".

Diagnosis.

Elaphe xiphodonta sp. nov. can be differentiated from its congeners by the combination of the following morphological characters: (1) medium body size, SVL 785 mm in single adult female; (2) dorsal scales in 21-21-17 rows, the medial 11 rows keeled; (3) supralabials seven or eight, third/fourth (right) or fourth/fifth (left) in contact with eye, infralabials 9 or 10; (4) ventral scales 202-204; (5) subcaudals 67-68; (6) loreal single, not in contact with eye, not in contact with internasals; (7) two preoculars (including one subpreocular), two postoculars; (8) two anterior temporals, three posterior temporals; (9) precloacal plate divided; (10) reduced teeth number in maxilla and dentary bones (MT 9+2, DT 12; (11) sharp edges on the posterior or posterolateral surface of the rear MT and DT; (12) top of head yellow, three distinct markings on head and neck; (13) a distinct black labial spot present on supralabials; (14) ground color of dorsum yellow, 46-49 entire (or incomplete) reddish brown blotches with black edges on body and 12-19 similarly colored spots on tail; (15) ventral surface of body yellow with mottled irregular black blotches, a few irregular small red spots dispersed on middle of ventral scales.

Description of holotype.

Adult female (Figs 1 , 2 , 3A ). Body and tail slender, TL 967.5 mm (SVL 785.2 mm, TaL 182.3 mm, TaL/TL: 0.19); dorsal scales in 21-21-17 rows, the medial 11 rows keeled, the vertebral scales not enlarged; head elongate, moderately distinct from neck, longer than width and narrow anteriorly, HL 26.5 mm, HW 18.1 mm (HW/HL: 0.68); eye medium, ED 3.2 mm, pupil elliptic; rostral triangular, broader than high, RW 7.1 mm, RH 4.5 mm (RW/RH: 1.58; RW/HW: 0.39), visible from dorsum; nostril laterally pointed, located in the middle of nasal; nasal divided into two scales by nostril; two internasals, anteriorly rounded, bordered by two large prefrontals posteriorly; frontal single and enlarged, narrowed posteriorly; parietals paired, longer than width, in contact with each other medially, with upper anterior and posterior temporals laterally; one loreal on each side, in contact with nasal anteriorly, preocular posteriorly, prefrontals dorsally and the second supralabial ventrally; one enlarged preocular in contact with eye and supraocular posteriorly, prefrontal and loreal anteriorly, a smaller subpreocular ventrally, and not in contact with frontal; subpreocular in contact with eye and the third supralabial posteriorly, the second supralabial anteriorly, and preocular dorsally; two postoculars, upper one in contact with eye anteriorly, supraocular and parietal dorsally, and upper anterior temporal posteriorly, bottom one in contact with eye anteriorly, with upper and lower anterior temporals posteriorly, fifth and sixth supralabials below on left, and with fourth and fifth supralabials below on right; eight supralabials on left, seven supralabials on right (the third and the forth merged relative to left), first and second in contact with nasal, fourth and fifth reaching orbit on left, third and fourth reaching orbit on right; ten infralabials on left, nine infralabials on right, first pair in broad contact with each other, first to fifth in contact with anterior pair of chin shields, fifth in contact with posterior chin shields, fifth infralabial bipartitioned, lower part obviously larger than upper one; two pairs of chin shields, elongate, anterior pair larger, first pair meeting in midline, posterior pair is separated by three small scales; two similarly sized anterior temporals on left, lower one divided into two small scales on the right; three similarly sized posterior temporals on each side; 204 ventrals, excluding two preventrals; 67 pairs of subcaudals, excluding tail tip; precloacal plate divided.

Coloration in life.

Dorsal surface of head yellow, three distinct markings on head and neck; the anterior transverse black stripe, somewhat reddish medially, extends from the posterior margin of rostral and through the each eye to last two supralabials and adjacent small scales; interorbital arcuate cross-band, covering anterior part of frontals, most part of prefrontals, top of supraoculars, bottom half of upper postoculars, intact bottom postoculars, bottom half of upper temporals, most of bottom of temporals, dorsal edge of sixth left supralabials (fifth on the right), dorsal half of seventh supralabials (sixth) and bottom half of posterior-most supralabials, not reaching internasals, connected to largest posterior marking from mediolateral part; largest marking is a distinct black “M” -shaped marking that is reddish medially, covering the posteromedial part of the frontals, posterior part of supraoculars, most of parietals, dorsal margin of upper temporals, posteriorly extended, forming two thick black-edged reddish brown stripes on nape. Lateral surface of head yellow, a few small black spots dispersed on supralabials (2, 4 and 5 on left and 2, 3 and 4 on right) and subpreocular, a distinct scutellate black labial spot on the junction of the 2, 3 and right subpreocular (absent on left). Ventral surface of head consistently light-yellow, a few small black spots dispersed on the mental, infralabials, and anterior chin shields. An irregular spot occurs on the posterior edge of the junction of two anterior chin shields. Mouth lining is pale-heather and tongue is black.

Ground color of dorsal surface yellow, 49 complete or incomplete, black-edged reddish brown blotches on body and 12 similarly colored spots on tail; dorsal blotches on body approximately three to five scales in length, and eight to eleven scales rows in width; each blotch is usually composed of reddish brown scale with dark-brown edges. Two rows of smaller, black-edged reddish brown blotches on both side of the larger mid-body blotches, alternating with the mid-body blotches, each blotch covers 2-4 dorsal scales and separated from ventral scales by two rows of the dorsolateral scales. Ground color of ventral surface is yellow, mottled with irregular black blotches, a few irregular small red spots scattered midventrally.

Intraspecific variation.

Measurements, body proportions and scale and pattern counts of the two specimens are listed in Table 5 . The third and fourth supralabials are merged on right in holotype, which leads to the different supralabial counts. Regardless of the slight variation in scalation among the type series of E. xiphodonta sp. nov., the color pattern varies considerably between the juvenile and the adult: In adult one (SYS r002534, holotype), the color of the rostral, top and side of head, and chin, as well as dorsal and ventral sections of body are consistently light-yellow, whereas in the juvenile (IVPP OV 2721), the color of head and dorsal body is greyish to olive-green; the ventral scales and subcaudal scales are oyster white, with irregular greyish black spots. The juvenile has a similar dorsal pattern as the adult.

Skull.

The osteological description is based on a road-killed juvenile individual (Paratype, IVPP OV 2721, Figs 5 , 6 ). The skull is nearly completely preserved except for the slightly crushed parietal, and basioccipital bones.

Snout (Fig. 5 ). The premaxilla is short and blunt. The ascending process is laterally expanded and slanted posteriorly as in many borrowers (e.g., Euprepiophis and Archelaphe ), rendering it hourglass-shaped in anterior view. The transverse process of premaxilla is flat, triangular-shaped in dorsal view. The posterior end of vomerine process of premaxilla contacts the tip of both vomer and septomaxilla. The posteromedial surface of vomerine process is expanded and oval shaped. The anterior section of the dorsal plate of nasal is tapered while the posterior section is expanded as oval shaped. The dorsal surface is slightly bulged.

Braincase (Fig. 5 ). The parietal is blunt and rounded, lacks a lateral crest on each side. The prefrontal is slender, somewhat rectangular. The anterolateral process is blunt. The anterior margin of frontal presents as trapezium-shaped. The lateral margin slightly concave. The postorbital is crescent-shaped, the anterodorsal process does not contact the frontal. The ventral process of postorbital is tapered, not furcated. The supraoccipital is rectangular and compressed, bearing a trifurcated dorsal ridge. The basisphenoid is wide and flat, with no conspicuous ridges on the ventral surface. The rostrum of parasphenoid is not divided. The angular surface between the basisphenoid and basioccipital is smooth. The columella is stubby, the shaft of columella quite short, approximately 1.2 times as length as the diameter of foot plate. The foramina for maxillary branch of trigeminal (f5b) and mandibular branch of trigeminal (f5c) nerves are oval shaped, not reaching the margin of prootic. The f5b is approximately 1/2 the width of f5c.

Palatomaxillary arch

(Fig. 6 ) The maxilla is slender. The maxillary nutrient foramen is transversely elongate, oval shaped and opens on the anterolateral side at the level of the third maxillary tooth and perforates the maxilla laterally. The anterior portion of maxilla curves slightly inward. The palatine process of maxilla is elongate while the ectopterygoid process is short and bunt.

The maxilla has 11 teeth on each side, with one or two rows of replacement teeth on the lingual side. In contrast to other species of Elape , the maxillary dentition of the new species is conspicuously differentiated. The anterior five MT have inconspicuous posterolateral ridges, while the posterior six teeth have a sharply edged ridge on their posterior margin (which could be also described as: the posterolateral ridge gradually moved posteriorly by the MT row, forming a sharp cutting edge on the posterior MT), forming blade-like teeth. The MT increase in size posteriorly, the posterior-most two being the largest, not separated from the anterior teeth by a diastema. The cutting edges of the posterior four MT slightly posteriorly convex, rendering them kukri shaped.

The palatine bears nine teeth, with one row of replacement teeth on the labial side. The choanal process of palatine (chp) forms a right triangular in dorsal view. The anterolateral margin of the maxillary process forms an approximate 30° angle with the medial line. The posterior margin of maxillary process is perpendicular to the medial line and collinear with the anterior margin of the choanal process. The pterygoid is slender and lanceolate in shape, 1.8 times the length of palatine, bearing 12 solid teeth (with one row of replacement teeth on the labial side). The ectopterygoid process and the medial transverse process of pterygoid are very small and difficult to see. The ectopterygoid is horizontally expanded, and outwardly curved in dorsal view. The labial furcula of ectopterygoid is oval, and distinct from the lingual process. The medial furcula (medial process) is elongate and spiculate, slightly curved ventrally.

Suspensorium and mandible

(Figs 5 , 6 ) The mandible is slender and moderately curved. The supratemporal is flat and slender, fusiform, and the anteroventral margin is slightly angulated upward. The quadrate is triangulated in lateral view, and approximately the same length as supratemporal. The supratemporal angular surface of the quadrate is expanded, elongated and oval shaped. The prearticular crest (pcr) of the compound bone is prominent while the surangular crest (sac) is absent. The angular is slender and triangular. The splenial is triangular, coracoid shaped and shorter than angular. The dental bone bears 13 teeth, decreasing in size at the fifth tooth, with one or two rows of replacement teeth on the lingual side. The posterior tip of dorsal process of dentary extends farther posteriorly than the ventral process. The largest dentary nutrient foramen is elongated-oval shaped and lies below the seventh tooth.

Dentition

(IVPP OV 2721, paratype) Maxilla: 11/11 (9+2); pterygoid: 12/12; palatine: 9/9; dentary: 13/13. Dentitional comparisons within the genus Elaphe and some related colubrid groups are listed in Table 6 .

Comparisons.

Detailed comparisons among Elaphe species are given in Table 7 and Fig. 7 .

Elaphe xiphodonta sp. nov. is distinct from all of its congeners by having fewer MT, enlarged posterior MT, cutting edges on both MT and DT, and three rows of large, black-bordered reddish brown dorsal blotches.

Additionally, Elaphe xiphodonta sp. nov. can be distinguished from E. cantoris , E. climacophora (Boie, 1826), E. hodgsoni , E. moellendorffi , and E. taeniura by having fewer ventral scales (202-204 vs. 226-239 in E. cantoris , 222-236 in E. climacophora , 228-247 in E. hodgsoni , 270-278 in E. moellendorffi , and 223-261 in E. taeniura ), fewer subcaudals (67-68 vs. 78-87 in E. cantoris , 97-116 in E. climacophora , 72-92 in E. hodgsoni , 92-102 in E. moellendorffi , and 73-121 in E. taeniura ), smaller body size (SVL 785 mm in single adult female vs. maximum SVL 1158 mm in E. cantoris ,> 2000 mm in E. climacophora , 1190 mm in E. hodgsoni , 1602 mm in E. moellendorffi , and> 2000 mm in E. taeniura ), and vastly different color pattern (Table 7 ).

Elaphe xiphodonta sp. nov. can be differentiated from E. quatuorlineata Lacepede, 1789, E. sauromates (Pallas, 1811) and E. urartica (Jablonski, Kukushkin, Avci, Bunyatova, Ilgaz, Tuniyev & Jandzik, 2019) by having fewer dorsal scale rows (21-21-17 vs. 25-25 (23-27)-19 in E. quatuorlineata , 25 (21-27)-25 (23, 24)-19 (18-21) in E. sauromates and 25 (23, 24)- 25 (23, 24)-19 (18) in E. urartica ) and a vastly different color pattern. Beyond that, E. xiphodonta sp. nov. can be further differentiated from E. quatuorlineata and E. sauromates by its smaller body size (SVL 785 mm in single adult female vs. maximum SVL> 2000 mm in E. quatuorlineata and 1250 mm in E. sauromates ).

Elaphe xiphodonta sp. nov. can be differentiated from Elaphe carinata , E. davidi and E. quadrivirgata (Boie, 1826) by its smaller body size (SVL 785 mm in single adult female vs. maximum SVL> 2000 mm in E. carinata , 1227 mm in E. davidi , and> 1000 mm in E. quadrivirgata ), having fewer subcaudals (67-68 vs. 69-102 in E. carinata , 70-96 in E. quadrivirgata ), and a vastly different color pattern.

Despite the morphological similarities to E. bimaculata , E. dione , and E. zoigeensis , Elaphe xiphodonta sp. nov. differs from them by having different dorsal scale row counts (21-21-17 vs. 23 (23-25)-23 (21-25)-19 (21) in E. bimaculata ), fewer preoculars (2 vs. 3 in E. zoigeensis ), fewer MT (11/11 vs. 19/20 in E. bimaculata , 16-20 in E. dione , and 14-17 in E. zoigeensis (Table 6 ), blade-like posterior MT and the unique color pattern within the genus Elaphe .

Molecular phylogeny.

The ML and BI analyses produced identical topologies, which were integrated in Fig. 8 . The pairwise distances based on CO1 and cytb genes among all species are given in the Tables 3 , 4 , respectively.

The phylogenetic analyses recovered a strongly supported monophyletic lineage containing all Elaphe (BS 100; BPP 1.00) which can be divided into three strongly supported clades (BS 95-97; BPP 1.00). Clade 1 includes all species previously in the genus " Orthriophis " with strong nodal support (BS 95; BPP 1.00). Notable intraspecific genetic differentiation within E. taeniura (mean p -distances 6.8% in CO1, 5.4% in cytb), pertains to different geographical clades.

The two samples from Chengguan Town, Shaanxi are clustered together with strong support (BS 100; BPP 1.00) with nearly no molecular divergence (mean p -distances 0% in CO1, 0% in cytb) between them. The clade of the above-mentioned specimens constitutes a sister clade with E. zoigeensis (Clade2, mean p -distances 8.4% in CO1, 13.3% in cytb).

Within Clade 3, the relationship between Elaphe anomala and E. schrenckii are worth noting. These two species form a strongly supported monophyletic group (BS 100; BPP 1.00) bearing low interspecific molecular divergence (mean p -distances 0.0% in CO1, 0.4% in cytb), suggesting they may be different color morphs of the same species, as mention before ( An et al. 2010). However, given their distinctive color pattern differences and obvious geographical separation, we follow the current taxonomy.

Based on their phylogenetic relationships, genetic differentiation, and morphological distinctiveness (see Taxonomic accounts below), we hypothesize that the population from Chengguan Town, Shaanxi represents a separately evolving lineage and should be described as a new species.

Distribution, ecology and habit.

Elaphe xiphodonta sp. nov. is currently known only from the Chengguan Town, Ningshaan County, Shaanxi Province, China. The new species inhabits sunny or semi-sunny gravels and bushes on slopes of less than 20°, along Chang’an River with an average width of 3 m. Elevation of the habitat ranges from 1700 to 1900 m. The vegetation types are Abies fargesii forest with artificial Picea asperata , Salix fargesii , Rubus koereana , Betula albosinensis and Fargesia qinlingensis . The canopy density is 0.75 ( Bu and Zheng 2015). The new species is sympatric with Nanorana unculuanus , Scutiger ningshanensis , Euprepiophis perlaceus , Rhabdophis nuchalis , Stichophanes ningshaanensis , Gloydius qinlingensis and Protobothrops jerdonii (Fig. 9 ). When being captured, the new species flattens its head triangular and releases scent from the cloacal scent glands with smells a bit similar to P. jerdonii .

In feeding habits, the fecal samples from the holotype were checked and contained only feathers, indicating that this species is at least a bird-eater. The holotype was observed to prey on captive nesting quail and quail egg.

Figures

Figure 1. General view of the holotype (SYS r 002534) of Elaphe xiphodonta sp. nov. in life. Photo by Shuo Qi.

Figure 2. Detailed pholidosis of the head of the holotype (SYS r 002534) of Elaphe xiphodonta sp. nov. Photos by Shuo Qi, illustrated by Xue-Man Zheng.

Figure 3. Comparison between Elaphe xiphodonta sp. nov. and sympatric Protobothrops jerdonii in different age stages A adult Elaphe xiphodonta sp. nov. (SYS r 002534, holotype) B adult Protobothrops jerdonii C juvenile E. xiphodonta sp. nov. (IVPP OV 2721, paratype), road-killed specimen D juvenile P. jerdonii specimen in preservative. The black arrow points to the labial spot. Photos A, B, D by Shuo Qi, photo C by Liang Sun.

Figure 4. Type terra of Elaphe xiphodonta sp. nov (marked with red triangles), with the collection localities of some other Chinese species of Elaphe.

Figure 5. Three-dimensional model of the skull of Elaphe xiphodonta sp. nov. (IVPP OV 2721, paratype). Left, dorsal view; middle, ventral view; right, lateral view. (Right palatomaxillary arch, mandible and suspensorium are not shown). Implemented by Peng-Fei Yin, Ye-Mao Hou and Jing-Song Shi.

Figure 6. Palatomaxillary apparatus and mandibles of Elaphe xiphodonta sp. nov. (IVPP OV 2721, paratype). Implemented by Peng-Fei Yin, Ye-Mao Hou and Jing-Song Shi A ventral (A 1) and dorsal (A 2) view of left palatomaxillary apparatus B posterolateral view of left maxilla (B 1) and right dentary (B 2), with cutting edges (ce) and caudolateral ridges indicated C labial (C 1, right), ventrolateral (C 2, left), ventral (C 3, right, mirrored) and dorsal (C 4, left) view of maxilla D Labial (D 1) and lingual (D 2) view of right dentary E labial (E 1), lingual (E 2), ventral (E 3) and dorsal (E 4) view of right mandible. Abbreviations: an. angular, at. atlas, ax. axis, bo. basioccipital, bs. basisphenoid, bt. blade teeth (" xiphodont "), ce. Posterior cutting edge of the blade teeth, chp. choanal process of palatine, clr. caudolateral ridge of the teeth, cp. compound bone, d. dentary, dpd. dorsal process of dentary, ecp. ectopterygoid, epm. ectopterygoid process of maxilla, etp. empty tooth position, exo. exoccipital, f. frontal, f 5 b. foramen for maxillary branch of trigeminal, f 5 c. foramen for mandibular branch of trigeminal, lf. lacrimal foramen, lfe. lateral furcula of ectopterygoid, m. maxilla, na. nasal, mfe. mesial furcula of ectopterygoid, mp. maxillary process of palatine, nf, nutrient foramen, p. parietal, pcr. prearticular crest of compound bone, pfr. prefrontal, pmx. premaxilla, po. postorbital, pp. palatine process of maxilla, pro. prootic, psp. parasphenoid rostrum, pt. pterygoid, pVf. posterior Vidian foramen, rpt. replacement teeth, sac. surangular crest of compound bone, smx, septomaxilla, so. supraoccipital, sp. splenial, st. supratemporal, v. vomer, vpd. ventral process of dentary, fs. fracture surface.

Figure 7. Comparisons of general morphological characteristics with its congeners in China A Elaphe xiphodonta sp. nov. (SYS r 002534, holotype), Ningshaan, Shaanxi, by Shuo Qi B E. anomala, Benxi, Liaoning, by Shuo Qi C E. bimaculata, Hong'an, Hubei, by Chong-Jian Zhou D E. cantoris, Bome, Tibet, by Jing-Song Shi E E. carinata, Mentougou, Beijing, by Jing-Song Shi F E. davidi, Benxi, Liaoning, by Jing-Song Shi G E. dione, Yongdeng, Gansu, by Shuo Qi H E. hodgsonii, Gyirong, Tibet, by Shuo Qi I E. moellendorffi, Chongzuo, Guangxi, by Jia-Jun Zhou J E. schrenckii, Baishan, Jilin, by Shuo Qi K E. taeniura from Hangzhou, Zhejiang, by Wei-Liang Xie L E. zoigeensis, Jiuzhaigou, Sichuan, by Jin-Wang.

Figure 8. Bayesian inferenced topology of 13 Elaphe species, based on the four partial mitochondrial DNA sequences (12 S rRNA, 16 S rRNA, CO 1 and Cytb genes). BPP and BS values, respectively, occur at the nodes.

Figure 9. Habitats of Elaphe xiphodonta sp. nov. (Ningshaan County, Shaanxi), Provide by Shu-Hai Bu.