Diploderma yangi, Wang & Zhang & Li, 2022

Wang, Kai, Zhang, Yinpeng & Li, Xianqi, 2022, A New Species of Diploderma (Reptilia: Squamata: Agamidae) from the upper Salween River in Eastern Tibet, China, Zootaxa 5099 (2), pp. 201-220 : 209-217

Diploderma yangi sp. nov.

( Table 3 , 4 ; Fig. 3–6 )

ZooBank urn:lsid:zoobank.org:act:83878ED4-046E-4D75-B88E-E1684226BE5A

Chresonyms. Japalura flaviceps Zhao & Yang 1997: 165–167 ; Zhao et al. 1999: 111–115; Japalura laeviventris Rao et al. 2017 .

Holotype. SWFU 005414 , adult male, from Cawarong Village , Zayu County, Tibet Autonomous Region, China (28.479ºN, 98.4656ºE, elevation 1887 m). Collected by Liu Xiaolong , Li Xianqi , and Tie Minhua on 6 September 2020.

Paratypes. SWFU 005415 , 006812 , adult males ; SWFU 005417 , 005418 , subadult males ; SWFU 005410–13 , 005419 , adult females. All share the same locality and collector information as the holotype .

Etymology. The new species name is derived from the last name of Chinese herpetologist, Dr. Datong Yang, from Kunming Institute of Zoology, Chinese Academy of Sciences. We name the new species after Dr. Yang in honoring his pioneer works and lifetime contributions to the herpetological research in the Hengduan Mountain Region in China. We suggested Zayu Mountain Dragon as its English common name, and 察MAENJ (Pinyin: Chá Yú Lóng Xî) as its Chinese common name.

Diagnosis. Diploderma yangi sp. nov. can be diagnosed from congeners by a combination of the following morphological characters: (1) adult body size moderate, SVL 57.8–64.5mm in adults; (2) tail long, TAL 202.8–216.6% SVL in males, 196.8–208.8% in females; (3) head width moderately wide, HW 69.0%–73.9% HL; (4) hind limbs long, HLL 69.6–86.3% SVL; (5) tympanum concealed; (6) crest scales small and numerous, MD 45–59; (6) feeble skin fold under nuchal crest in males, no skin fold under dorsal crest; (7) conical scales present on post temporal, post tympanic, and post rictal regions, each bearing 3–6 keels, POS 2–6, PTY 2–7, PRS 2–6; (8) F4S 14–18, T4S 20–24; (9) NSL mostly 1, rarely 0; (10) transverse gular fold present, distinct; (11) ventral head and body scales strongly keeled; (12) distinct radial dark stripes present around eyes; (13) dorsal background coloration Pale Pinkish Buff (Color 3), speckled with Warm Sepia (Color 40) to Dusky Brown (Color 285) spots laterally inferior to dorsolateral stripes; (14) dorsolateral stripes smooth edged and Pale Emerald Green (Color 141) to Light Pistachio (Color 101) in males, slightly wavy and Pale Buff (Color 1) to Pinkish Buff (Color 3) in females; (13) gular spot present in both sexes, Pale Emerald Green (Color 141) to Light Pistachio (Color 101), paler in females; and (14) oral cavity and tongue pale Light Flesh Color (Color 250).

Comparisons. Diploderma yangi sp. nov. is phylogenetically sister to and morphologically most similar to D. laeviventre , but D. yangi sp. nov. can be differentiated from the latter by the presence of well-developed conical scales in the post-tympanic and post-rictal regions of the head (vs. absence), strongly keeled ventral body scales (vs. smooth), a different coloration of dorsolateral stripes (Pale Emerald Green [Color 141] to Light Pistachio [Color 101] in males, Pale Buff [Color 1] to Pinkish Buff [Color 3] in females vs. Cream Color [Color12] in males, Sulphur Yellow [Color 80] in females), and a distinct coloration of gular spots (Pale Emerald Green [Color 141] to Light Pistachio [Color 101] in both sexes vs. Light Chrome Orange [Color76] in both sexes) ( Table 3 ).

Diploderma yangi sp. nov. was confused with D. flaviceps , but the new species differs from the latter by having a tendency toward fewer SL (7–9 vs. 9–11), smooth edged, Pale Emerald Green (Color 141) to Light Pistachio (Color 101) dorsolateral stripes in males in life (vs. strongly jagged, Pale Horn Color [Color 11]), presence of distinct radial stripes around the eyes (vs. absence), presence of gular spots in both sexes (vs. absence), absence of skin folds under nuchal crest in females in life (vs. presence), and absence of dark reticulated patterns on gular region (vs. presence) ( Table 3 ).

For congener that is from the same river valley downstream, D. yangi sp. nov. differs from D. slowinskii by having concealed tympana under fine scales (vs. exposed), a much smaller body size (maximum body size 64.1 mm vs. 99.5 mm), less developed and less keeled conical scales on post temporal regions of the head (vs. strongly developed with multiple keels), the presence of gular spots in both sexes (vs. absence in both sexes), and a terrestrial lifestyle (vs. arboreal) ( Table 3 ).

From the remaining allopatric species in the Hengduan Mountain Region (isolated by snow covered mountains of over 4000 m; Fig. 1 ), D. yangi sp. nov. differs from D. drukdaypo , D. dymondi , D. fasciatum , D. micangshanense , D. panlong , D. splendidum , D. swild , D. varcoae , and D. vela by the presence of colorful gular spots in both sexes (vs. absence); from all but D. aorun , D. batangense , D. flavilabre , D. grahami , D. hamptoni , D. yulongense and D. zhaoermii (i.e. D. angustelinea , D. bowoense , D. brevicauda , D. chapaense , D. formosgulae , D. iadinum , D. menghaiense , D. panchi , D. qilin , D. yunnanense ) by having a distinct coloration of gular spots (Pale Emerald Green [Color 141] to Light Pistachio [Color 101] in both sexes vs. blue, yellow, orange, or pinkish red); from D. batangense , D. flavilabre , D. yulongense , and D. zhaoermii by having smooth dorsolateral stripes in males (vs. strongly jagged); and from D. grahami by having much longer tail (TAL 202.8–216.6% in males, 196.8–208.8% in females vs. 164.3%) and distinct transverse gular fold (vs. feeble). Additionally, the new species differ from D. brevicauda , D. drukdaypo , D. flavilabre , D. panchi by having a much longer tail (TAL 202.8–216.6% in males, 196.8–208.8% in females vs. <190% in males, <170% in females); from D. aorun , D. batangense , D. bowoense , D. formosgulae , D. qilin , D. yulongense , and D. zhaoermii by having smooth dorsolateral stripes in males (vs. strongly jagged); from D. iadinum , D. micangshanense , D. varcoae , and D. zhaoermii by having more middorsal crest scale (45–59 vs. ≤43); from D. angustelinea by the presence of distinct black radial stripes around eyes (vs. absence) and different shape of dorsolateral stripes in males (smooth edged and wide vs. slightly jagged and narrow); from D. chapaense , D. fasciatum , D. hamptoni , D. menghaiense , D. micangshanense , D. varcoae , D. yunnanense , and all five species from East Asian Islands ( D. brevipes , D. luei , D. makii , D. polygonatum , and D. swinhonis ) by the presence of a transverse gular fold (vs. absence); and from D. dymondi , D. varcoae , D. swild , and D. panlong by having concealed tympana (vs. exposed).

Description of holotype. Adult male, body not compressed, SVL 55.9 mm; tail long, slender, TAL 121 mm, 216.6% SVL; forelimb 26.2 mm on left, 46.8% SVL; hindlimb 43.6 mm on left, 78.0% SVL. Head relatively robust, HW 73.9% HL, HD 73.1% HW; SEL 38.1% HL. Rostral rectangular, bordering seven small postrostral scales; dorsal head scales heterogeneous, all strongly keeled; single distinct Y-shaped ridge on dorsal head, stem of Y-shaped ridge consisting of three enlarged, protruding scales along lateral midline of snout from midpoint between nasal to midpoint between anterior to edges of first supraciliaries of each side; single enlarged, protruding scale post supraciliary on each side, sub-pyramidal in shape, each bearing 3 or 4 keels; POS 6/4, conical in shape, each bearing 2 or 3 keels, one of each side strongly protruding, larger than remaining ones. Nasal rounded, separated from first supralabial by single row of scales; loreals small, keeled; suborbital scale rows 3/3, keeled; canthus rostralis elongated except last two posteriorly, greatly overlapping with each other, 10/10; enlarged, keeled scales forming single lateral ridge from posteroinferior eye to posterosuperior tympanum on each side, 8/7; tympana concealed under fine scales; SL 8/8, feebly keeled. Mental triangular; IL 7/9, first pair not in contact; enlarged chin shields 4/6, weakly keeled, first one contacting IL on each side, remaining ones separated from IL by single row of small scales; ventral head scales homogeneous in size, strongly keeled; gular scales 29, homogeneous, distinctively keeled, slightly smaller or equal to ventrals; distinct transverse gular fold present; gular pouch well developed in life, reduced after preservation.

Distinct shoulder fold present, short; dorsal body scales heterogeneous in size and shape, all keeled, each bearing single lateral keel; axillary scales fine, much smaller than remining dorsals; enlarged dorsal scales forming two lateral rows from neck to pelvis on each side of dorsal crest: first row two scales away from dorsal crest, second row along inferior edge of dorsolateral stripe; remaining enlarged dorsal scales randomly scattered. Nuchal crest scale triangular, larger and differentiated from dorsal crests in shape, TNC 4.8% HL; dorsal crest scale in fan-shape, tip pointing anteriorly, each bearing single lateral keel, slightly raised posteriorly; feeble skin fold under nuchal crest; dorsal crest scales low without skin folds; MD 49. Dorsal limb scales strongly keeled, mostly homogeneous, except a few enlarged, conical scales on postaxial thighs; F4S 16/15, T4S 22/21. Ventral body scales 59, homogeneous, all distinctively keeled, mostly carinate in regular lateral rows. Ventral limb scales homogeneous, slightly larger than ventrals, all distinctively keeled, carinate in regular rows along proximal-distal axis. Tail scales all distinctively keeled, heterogeneous at anterior most 1/5 of length dorsally, with enlarged scales continuing from dorsal crest along medial axis and along dorsolateral line on each side; 13 enlarged scales aliened roughly along medial axis on ventral tail five scales posterior to posterior cloaca lip; remaining tail scales homogeneous, strongly keeled, carinated.

Coloration. In life, the dorsal and lateral surfaces of head are Pale Pinkish Buff (Color 3) to Buff (Color 5), darker on the dorsal side. Clay Color (Color 18) to Sepia (Color 286) radial stripes are present around the eyes, with the posteroinferior stripe widest and darkest, and the remaining inferior stripes much narrower and fainter. Three Sepia (Color 286) transverse streaks are present on dorsal surface of the head, with the first one anterior to eyes, the second one between eyes, and the last one posterior to the eyes. Clay Color (Color 18) to Sepia (Color 286) speckles and short streaks are present on the remaining areas of dorsal and lateral surfaces of head.

The background coloration of dorsal and lateral surfaces of the body is Beige (Color 254) to Pale Cinnamon (Color 55). Single Jet Black (Color 300) triangular patch is present along the posterior side of shoulder fold. A distinct, smooth-edged, Light Pistachio (Color 101) dorsolateral stripe is present from the neck to the pelvis close to the dorsal crest on each side. Six rectangular or triangular, Raw Umber (Color 23) to Jet Black (Color 300) patches are evenly scattered from neck to the pelvis along the vertebral line between the dorsolateral stripes. The region adjacent to the inferior edge of dorsolateral stripes on each side is Raw Umber (Color 23) to Jet Black (Color 300), which then gradually transitions to the lighter background coloration of lateral body. Raw Umber (Color 23) to Jet Black (Color 300) speckles are scattered on the lateral surface of body. Dorsal surfaces of limbs and tail are Beige (Color 254) to Pale Cinnamon (Color 55). Raw Umber (Color 23) to Jet Black (Color 300) transverse bands are evenly scattered from the proximal to the distal end on limbs, and from anterior to posterior end on the tail.

The ventral surface of the head is uniform white. A triangular, Light Pistachio (Color 101) gular spot is present on the posterior gular region. Ventral surfaces of the body, limbs, and tail are uniform white or Pale Buff (Color 1) with no ornamentation patterns. The oral cavity and tongue pale Light Flesh Color (Color 250).

In preservation, the ornamentation patterns remain the same as in life, but the coloration fades away. Specifically, the background coloration of dorsal and lateral surfaces of head and body become Pale Neutral Gray (Color 296), all the darker ornamentation patterns (i.e. radial stripes around the eyes, transverse bands on dorsal surface of head and limbs, and rectangular patches along the dorsal midline of body) all become Medium Neutral Gray (298) to Dark Neutral Gray (Color 299), and the dorsolateral stripes and the gular spot become Light Venetian Blue (Color 165).

Variations. Detailed morphological variation are summarized in Table 4 . Sexual dichromatism are evident in the new species, in which the males have larger gular spots, and smooth, Pale Emerald Green (Color 141) to Light Pistachio (Color 101) dorsolateral stripes (vs. shorter tail, smaller gular spots, and irregular and wavy, Pale Buff [Color 1] to Pinkish Buff [Color 3] dorsolateral stripes in females). The male holotype has a much longer tail than the females (TAL 216.6% SVL vs. 196.8–208.8% in females, n = 4), but given the limited sample size of adult males, we cannot conclude on the sexual dimorphism with confidence.

Natural history and conservation. Diploderma yangi sp. nov. is known from the upper Salween River Valley in Zayu County, Tibet Autonomous Region, China. While the upper distribution limit of the new species with respect to D. laeviventre is unknown, the lower distribution range of the new species is at the Tibet-Yunnan border region. Interestingly, the distribution border between D. yangi sp. nov. and D. slowinskii matches the climatic turnover between hot-dry valley climate and subtropical moist climate along the upper Salween River, and the climatic factor might have initiated the speciation between the two species and kept them from hybridization. Future ecological and evolutionary studies are needed to test this hypothesis.

The species is terrestrial, inhabiting the shrublands of the hot-dry Salween Valley ( Fig. 5 ). Population density was high, and individuals were observed resting under thick spiky bushes such as Sophora davidii , which were about 1.5m tall. Sympatric reptiles include Elaphe taeniura and Lycodon gongshan of the family Colubridae and Gloydius lipipengi of the family Viperidae , and the last two lizard-eating species may be the main predator of D. yangi sp. nov.. None of the collected females were gravid, suggesting that the survey time in September already passed the breeding season of the species. At the time of collection, the habitat at the type locality was still in good condition with no major constructions, but given the overlap between the habitat of the new species and human habitations along the upper Salween River, expected future expansion of township and infrastructures may pose threats to the species.

Figures

FIGURE 1. Distribution of the genus Diploderma on mainland East Asia. Star: type locality of Diploderma yangi sp. nov. in Cawarong (=Chawalong), Zayu County, Tibet, China. Circles: type localities of recognized congeners, which are the followings: 1. D. splendidum, 2. D. micangshanense, 3. D. zhaoermii, 4. D. grahami, 5. D. flaviceps, 6. D. panchi, 7. D. bowoense, 8. D. angustelinea, 9. D. panlong, 10. D. swild, 11. D. dymondi, 12. D. varcoae, 13. D. flavilabre, 14. D. batangense, 15. D. formosgulae, 16. D. aorun, 17. D. qilin, 18. D. yulongense, 19. D. brevicauda, 20. D. drukdaypo, 21. D. vela, 22. D. iadinum, 23. D. laeviventre, 24. D. slowinskii, 25. D. yunnanense, 26. D. menghaiense, and 27. D. chapaense.

FIGURE 3. Diploderma yangi sp. nov. in life. A1: holotype male SWFU 005414; A2: paratype female SWFU 005412; B1: unvouchered topotypic male; B2: unvouchered topotypic female. Photos by Xiaolong Liu and Jiansheng Peng.

FIGURE 4. Voucher specimen of the male holotype (A: SWFU 005414) and paratype (B: female SWFU 005412) of Diploderma yangi sp. nov.. 1: dorsal view; 2: ventral view. Photos by Yinpeng Zhang.

FIGURE 5. Head closeup views of the male holotype (A: SWFU 005414) and female paratype (B: SWFU 005412) of Diploderma yangi sp. nov. 1: dorsal head view; 2: lateral head view of the right side; and 3: ventral head view. Photos by Yinpeng Zhang.

FIGURE 6. Habitat at the type locality of Diploderma yangi sp. nov. near Cawarong Village, Zayu County, Tibet, China. Photo by Xiaolong Liu.