Southbound - the southernmost record of Tylototriton (Amphibia, Caudata, Salamandridae) from the Central Highlands of Vietnam represents a new species Author Phung, Trung My https://orcid.org/0000-0001-7086-8110 Dong Khoi 9 A, Tam Hiep, Bien Hoa, Dong Nai Province, Vietnam Author Pham, Cuong The https://orcid.org/0000-0001-5158-4526 Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi 10072, Vietnam & Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi 10072, Vietnam Author Nguyen, Truong Quang https://orcid.org/0000-0002-6601-0880 Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi 10072, Vietnam & Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi 10072, Vietnam Author Ninh, Hoa Thi Institute of Genome Research, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi 10072, Vietnam Author Nguyen, Huy Quoc https://orcid.org/0000-0003-3171-1561 Vietnam National Museum of Nature, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi 10072, Vietnam Author Bernardes, Marta https://orcid.org/0009-0008-2847-8862 Cologne Zoo, Riehler Str. 173, D- 50735 Cologne, Germany & Institute of Zoology, University of Cologne, Zuelpicher Str. 47 b, D- 50674 Cologne, Germany Author Le, Son Thanh National Institute of Medicinal Materials, 43 Đinh Tien Hoang, Ben Nghe, Ho Chi Minh city, Vietnam Author Ziegler, Thomas https://orcid.org/0000-0002-4797-609X Cologne Zoo, Riehler Str. 173, D- 50735 Cologne, Germany & Institute of Zoology, University of Cologne, Zuelpicher Str. 47 b, D- 50674 Cologne, Germany ziegler@koelnerzoo.de Author Nguyen, Tao Thien https://orcid.org/0000-0002-5640-4536 Institute of Genome Research, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi 10072, Vietnam text ZooKeys 2023 2023-07-03 1168 193 218 http://dx.doi.org/10.3897/zookeys.1168.96091 journal article http://dx.doi.org/10.3897/zookeys.1168.96091 1313-2970-1168-193 0100D617C5634A6FB57C1528B0F11446 14F80C51A01555D4A647F11DCC862EA9 Tylototriton ngoclinhensis sp. nov. Figs 2 , 3 , 4 , 5 , 6 , 7 , 8 Proposed common name: Ngoc Linh Crocodile Newt Material examined. Holotype . IEBR A.5130 ( Field No KT 2022.02), an adult male collected by T. M. Phung on 22 May 2022 in the montane evergreen forests of Ngoc Linh Natural Reserve , Dak Glei District , Kon Tum Province , Central Vietnam at 1.854 m a.s.l. Paratypes . IEBR A.5131, A.5132 ( Field No KT 2022.01, KT 2022.5), two adult males and IEBR A.5133, A.5134 ( Field No KT 2022.03, KT 2022.6), two adult females, collected by T. M. Phung ; IEBR A.5135 ( Field No KT 2022.4), an adult female, collected by S. T. Le on 20 May 2022 , the same collection data as the holotype . Figure 2. Dorsolateral view of Tylototriton ngoclinhensis sp. nov., holotype male (IEBR A.5130), in life. Etymology. The specific epithet ngoclinhensis refers to the type locality of the new species, Ngoc Linh Mountain in the Central Highlands of Vietnam. As common names, we suggest Ngoc Linh Crocodile Newt (English), Ca coc sần ngọc linh (Vietnamese). Figure 3. Dorsal views of the holotype B of Tylototriton ngoclinhensis sp. nov. (IEBR A.5130, male) and two paratypes A (IEBR A.5133, female) and C (IEBR A.5131, male) in preservative. Diagnosis. The new species is assigned to the genus Tylototriton and the subgenus Tylototriton Yaotriton based on the results of the molecular phylogenetic analyses and the following combination of morphological attributes: rough skin covered with fine warts, the presence of dorsolateral bony ridges on the head; the presence of dorsolateral glandular warts on the body; quadrate spine absent ( Nussbaum and Brodie 1982 ; Nishikawa et al. 2013a ; Le et al. 2015 ). Furthermore, the species is diagnosed from its congeners by the following combination of morphological characters: (1) size medium (SVL 60.8-66.5 mm, TL 57.6-61.8 mm in males, and SVL 72.5-75.6 mm, TL 62.9-67.9 mm in females); (2) head longer than wide; (3) parotoids very prominent and enlarged, projecting backwards; (4) tail length shorter than the snout-vent length; (5) vertebral ridge large, high, and glandular in appearance (6) 14 distinct dorsolateral glandular warts; (7) gular fold present; (8) tips of fore- and hind limbs overlapping when adpressed along the body; (9) tips of fingers reaching between eye and nostril when foreleg is laid forward; (10) dorsal surface and lateral sides of the head, upper and lower lips, rib nodules, vertebral ridge, peripheral area of the cloaca, and the ventral edge of tail with orange coloration; (11) presence of a distinct black line extending from the posterior end of the eye towards the shoulder. Figure 4. Ventral views of the holotype B of Tylototriton ngoclinhensis sp. nov. (IEBR A.5130, male) and two paratypes A (IEBR A.5133, female) and C (IEBR A.5131, male) in preservative. Description of holotype. A medium-sized male (SVL 66.5 mm, TL 59.5 mm). Head longer than wide (HW/HL 81.6%); head slightly concave on the top; snout short, truncate in dorsal view, slightly angular shaped in profile and protruding beyond lower jaw; nostril closer to the snout tip than to the eye; upper lip thick, fleshy and overlapping lower lip under the eye region; dorsolateral bony ridges on head prominent, moderately protruding, from above eye to above anterior end of parotoid, posterior ends relatively thick and scrolled inside; mid-dorsal ridge on head distinct and thin; parotoids enlarged, projecting backwards; tongue oval, attached to anterior floor of mouth, free laterally and posteriorly; vomerine teeth series in an inverted V-shape, converging anteriorly and reaching choanae; glandular vertebral ridge large, high, segmented tuberculate, extending from top of head to base of tail; rib nodules large, forming knob-like warts, distinctly isolated from each other, 14 on each side of body from axilla to base of tail; gular fold present. Limbs comparatively long, and slender; length of forelimbs approximately equal to hind limbs; relative length of forelimb FORE/SVL ratio 39.0%, relative length of hind limb HIND/SVL ratio 38.1%; tips of forelimb and hind limb overlapping when adpressed along the body; tips of fingers reaching between eye and nostril when foreleg is laid forward; fingers and toes well developed, free of webbing; fingers four, comparative finger lengths 1FL<4FL<2FL<3FL; toes five, comparative toe lengths 1TL<5TL<2TL<4TL<3TL. Tail length shorter than the snout-vent length (TL/SVL 89.5%); tail compressed laterally, the base relatively broad, tapering posteriorly, tail tip pointed; tail height less than the width at the tail base; dorsal fin fold relatively high; ventral side smooth. In general, the appearance of the tail is relatively low and flat. Dorsal skin very rough, with small granules and larger warts on dorsal surfaces of head and dorsum, lateral sides of body and tail; ventral skin with tubercles shaped like transverse wrinkles; throat with numerous tiny flat tubercles; surfaces of head ridges and middorsal vertebral ridge rough; limbs dorsally with numerous tiny tubercles, volar and plantar surfaces of hands and feet with tiny grooves forming reticulated pattern; flattened outer metacarpal and metatarsal tubercles distinct on palms and soles, respectively. Cloacal region slightly swollen, vent as a longitudinal slit, vent edges with numerous small transverse folds. Coloration in life. In life, ground color of dorsal and ventral surfaces black; dorsal surface and lateral sides of head and lower lips to jaw angles, rib nodules, vertebral ridge, the peripheral area of the cloaca and the ventral edge of the tail orange; tips of fingers, toes and elbow orange-brown. Coloration in preservative. The specimen in preservative is blackish brown. The orange coloration in life has faded to pale yellow. Secondary sexual characteristics. Males are probably smaller than females but sample size was small ( n = 3) and thus needs confirmation based on further records in the future. The female cloacal slit is short and its inner cloacal walls have no papilla. The male has papilla on its inner cloacal wall and its cloaca presents a long slit. Distribution. The new species is currently known only from the Ngoc Linh Nature Reserve, Kon Tum Province, in the Central Highlands of Vietnam (Fig. 5 ). Figure 5. Type locality of Tylototriton ngoclinhensis sp. nov. (yellow star) and congeners; elevations (from 0-1200+ m) increasing from green to brown (Tran Anh Tuan, after Sterling et al. 2006 ). Ecological notes. All specimens were collected during the day on the forest floor, under rotten trees or under moss, near a small rocky stream (Figs 6 , 7 ). The surrounding habitat at the type locality of the new species in Ngoc Linh Mountain was primary montane evergreen broadleaf forest, at elevations between 1,800 and 2,300 m asl. Figure 6. Habitat at the type locality of Tylototriton ngoclinhensis sp. nov. on Ngoc Linh Mountain. Figure 7. Tylototriton ngoclinhensis sp. nov. in its microhabitat at the type locality. Morphological measurements. Morphometric measurements of Tylototriton ngoclinhensis sp. nov. examined in this study are given in Table 3 . Table 3. Morphometric measurements (mm) of Tylototriton ngoclinhensis sp. nov. examined in this study.

Voucher	IEBR A.5130 Holotype	IEBR A.5131 Paratype	IEBR A.5132 Paratype	IEBR A.5133 Paratype	IEBR A.5134 Paratype	IEBR A.5135 Paratype
Sex	♂	♂	♂	♀	♀	♀
SVL	66.5	65.7	60.8	75.6	74.8	72.5
HL	20.6	19.9	18.9	23.8	22.2	21.5
HW	16.8	15.6	16.3	18.6	17.5	17.4
MHW	18.5	18.4	17.9	20.1	19.5	19.4
PL	11.5	11.4	11.2	13.5	12.1	12.4
PW	5.7	5.8	5.3	5.9	5.9	5.8
PH	5.9	6.3	5.2	6.5	6.2	6.1
EL	4.8	4.4	4.4	5.2	4.9	4.9
EN	4.2	4	3.9	4.8	4.6	4.5
IN	5.5	5.7	5.4	6.4	6.6	6.2
IE	8.4	8.2	8.5	9.8	9.5	9.4
LJL	14.1	13.6	13.7	17.1	16.1	16.6
UEL	2.5	2.6	2.2	2.8	2.5	2.6
HUM	9.2	8.4	8.7	9.5	9.4	9.3
RAD	16.7	15.6	15.8	17.6	17.3	17.2
FEM	8.7	8.2	8.3	8.8	8.9	8.6
TIB	16.6	15.9	16.8	17.8	18.1	17.2
FORE	25.9	24	24.5	27.1	26.7	26.5
HIND	25.3	24.1	25.1	26.6	27	26.2
TL	59.5	57.6	61.8	67.9	62.9	66.2
TH	7.2	7	7.5	8.2	7.2	7.6
CIL	7.4	6.9	6.7	5.9	5.5	5.8
CIW	4.9	4.6	4.3	3.7	3.5	3.5
WVr	4.2	4.5	3.8	4.4	4.2	4.1
L5W	3.2	3.1	2.7	3.5	3.3	3.4
AG	35.4	34.5	31.7	41.4	39.4	37.8
TkL	49.7	49.3	45.5	58.7	55.7	53.8
ToL	126	123.3	122.6	143.5	137.7	138.7

Morphological comparisons. We compared the new species with other members of the genus Tylototriton based on data obtained from the literature (Table 4 ). Table 4. Morphological comparisons between Tylototriton ngoclinhensis sp. nov. with other members of the subgenus Tylototriton Yaotriton (morphological data obtained from Fei et al. (1984) , Nussbaum et al. (1995) , Boehme et al. (2005) , Chen et al. (2010) , Stuart et al. (2010) , Hou et al. (2012) , Shen et al. (2012) , Nishikawa et al. (2013a , b ), Yang et al. (2014) , Phimmachak et al. (2015) , Fei and Ye (2016) , Hernandez (2016) , Qian et al. (2017) , Bernardes et al. (2017a , 2020 ), Li et al. (2020) , Lyu et al. (2021) , Poyarkov et al. (2021a) , Li et al. (2022) , Luo et al. (2022) . Abbreviations are as follows: TOL = total length, / = characters unobtainable from literature.

Species	TOL of males	TOL of females	Gular fold	Reach of finger tips when forelimbs stretched forward	Reach of tips of fore-and hind limbs when adpressed along body	Rib nodules shape	Vertebral ridge	Orange markings on the parotoid	Orange coloration on the rib nodules
Tylototriton ngoclinhensis sp. nov.	122.6-126.0	137.7-143.5	present	between the eye and nostril	overlapping	knob-like	segmented tuberculate	present	present
T. anhuiensis	118.9-145.7	103.8-165.4	present	/	meeting	slightly flattened	not segmented	absent	absent
T. asperrimus	118.0-138.0	149.0-202.0	present	reaching to the nostril or eye	meeting or overlapping	knob-like	not segmented	absent	absent
T. broadoridgus	110.4-140.3	138.9-162.5	absent	anterior corner of eye	not touched	slightly flattened	not segmented	absent	absent
T. dabienicus	120.3-135.3	134.9-155.5	present	anterior corner of eye	not touched	slightly flattened	not segmented	absent	absent
T. daloushanensis	/	/	present	eyes to nostrils	overlapping	slightly flattened	not segmented	absent	absent
T. hainanensis	137.0-148.0	125.0-140.0	present	eye	meeting or overlapping	slightly flattened	not segmented	absent	absent
T. liuyangensis	110.1-146.5	138.6-154.2	present	eye	not touched	slightly flattened	not segmented	absent	absent
T. lizhenchangi	145.6-173.0	150.0-156.5	present	Tip of snout	overlapping	slightly flattened	not segmented	absent	absent
T. maolanensis	151.0-172.0	142.7-170.5	present	beyond the snout	overlapping	knob-like	not segmented	absent	absent
T. notialis	109.1-130.4	141.8	present	/	/	knob-like	not segmented	absent	present
T. panhai	129.9-1603	160.0-166.8	present	/	/	knob-like	not segmented	present	present
T. pasmansi	/	160.0	present	eye	/	knob-like	not segmented	absent	absent
T. sini	118.4-124.5	144.5	present	/	overlapping	knob-like	not segmented	absent	absent
T. sparreboomi	/	/	present	nostril	/	knob-like	not segmented	absent	absent
T. thaiorum	116.1-138.0	/	present	/	overlapping	knob-like, in irregular series	not segmented	absent	absent
T. tongziensis	120.5-135.1	123.5-127.6	present	beyond the snout	overlapping	slightly flattened	not segmented	absent	absent
T. vietnamensis	113.0-121.8	/	absent	/	/	slightly flattened	not segmented	absent	absent
T. wenxianensis	126.0-133.0	/	present	nostril	meeting or overlapping	slightly flattened	not segmented	absent	absent
T. ziegleri	/	/	present	/	overlapping	knob-like	segmented tuberculate	absent	absent

Tylototriton ngoclinhensis sp. nov. differs from T. anhuiensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and tips of fore-and hind limbs overlapping when adpressed along the body (vs meeting); from T. asperrimus by having a smaller size in females (TOL 137.7-143.5 mm vs 149.0-202.0 mm), head longer than wide (vs head wider than long), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. broadoridgus by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and tips of fore and hind limbs overlapping when adpressed along the body (vs separated from each other); from T. dabienicus by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), tips of fore-and hind limbs overlapping when adpressed along the body (vs separated from each other), and finger tips reaching between eye and nostril when foreleg is laid forward (vs reaching anterior corner of eye); from T. daloushanensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on dorsolateral glandular warts (vs absent); from T. hainanensis by having a smaller size in males (TOL 122.6-126.0 mm vs 137.4-148.0 mm), head longer than wide (vs head wider than long), different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange marking on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and finger tips reaching between eye and nostril when foreleg laid forward (vs reaching eye); from T. joe by having larger size (TOL 122.6-126.0 mm vs 108-115 mm in males and 137.7-143.5 mm vs 121-128 mm in females), ventral edge of the tail orange, and tip of fingers, toes and elbow orange-brown (vs whole body dark brown but brownish tip of toes and tip of tail in some individuals); from T. liuyangensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), tips of fore-and hind limbs overlapping when adpressed along body (vs separated from each other), and finger tips reaching between eye and nostril when foreleg laid forward (vs reaching eye); from T. lizhenchangi by having a smaller size (TOL 122.6-126.0 mm vs 145.6-173.0 mm in males, TOL 137.7-143.5 mm vs 150.0-156.5 mm in females), different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange coloration on the dorsolateral glandular warts (vs absent), tips of fingers reaching between eyes and nostrils when foreleg laid forward (vs reaching to tip of snout), and the presence of orange markings on the parotoids (vs absent); from T. maolanensis by having a smaller size (TOL 122.6-126.0 mm vs 151.0-172.0 mm in males, TOL 137.7-143.5 mm vs 142.7-170.5 mm in females), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. notialis by different color pattern on head and vertebral ridge (orange vs dark brown), lower lip with orange marking (vs brown), and dorsolateral glandular warts and vertebral ridge distinctively large (vs small); from T. panhai by having a different ground color (black vs dark brown to brown), the presence of a distinct black line extending from the back of the eye towards the shoulder (vs less evident brownish line to absent line), dorsal edges of tail black (vs yellow, orange to reddish brown). Since T. panhai is the closest known taxon to Tylototriton ngoclinhensis sp. nov., additional morphological comparisons were made between the two species, especially between topotypic T. panhai type I and type II from Laos. Tail height was the only character (with n ≥ 3) that showed variation, presenting higher values both in males and in females (Fig. 8 ) of T. panhai , in relation to the new species. Figure 8. Comparison of average tail heights (mm) between Tylototriton ngoclinhensis sp. nov and T. panhai . The left side shows data for males ( A ) of Tylototriton ngoclinhensis sp. nov. ( n = 3; own data) and T. panhai ( n = 15; taken from Phimmachak et al. 2015 ), showing 2 standard deviation (2SD) bars, which represent 95% of the population. The right side shows data for females ( B ) of Tylototriton ngoclinhensis sp. nov. ( n = 3; own data) and T. panhai ( n = 3) including two data points from Phimmachak et al. (2015) , and one from Nishikawa et al. (2013a) ; averages marked by green horizontal lines, and ranges as vertical lines. The new species is distinguished from T. pasmansi by having rib nodules distinctively large (vs small), the presence of orange markings on the parotoid (vs absent), and the presence of orange colorations of the dorsolateral glandular warts (vs absent); from T. sini by different color pattern on head and vertebral ridge (orange vs dark brown), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and dorsolateral glandular warts distinct and large (vs small); from T. sparreboomi by different color pattern on head and vertebral ridge (orange vs dark brown), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and tips of fingers reaching between eye and nostril when foreleg laid forward (vs reaching nostril); from T. thaiorum by having head longer than wide (vs head wider than long), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. tongziensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. vietnamensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and the presence of gular fold (vs absent); from T. wenxianensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and finger tips reaching to between eyes and nostrils (vs reaching nostril); from T. ziegleri by having head longer than wide (vs head wider than long), different color pattern on head and vertebral ridge (orange vs dark brown), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. anguliceps , T. himalayanus , T. kachinorum , T. ngarsuensis , T. panwaensis , T. phukhaensis , T. podichthys , T. pulcherrimus , T. pseudoverrucosus , T. shanorum , T. shanjing , T. uyenoi , T. umphangensis , and T. verrucosus by having limbs and tail edges dark brown except for the orange digits, palms, and soles (vs limbs and tail edges uniformly orange or pale brown in the latter), the presence of a black line extending from the back of the eye towards the shoulder (vs absent); and from T. kweichowensis and T. yangi by different color pattern on tail (black vs uniformly orange in the latter), and ventral side dark brown (vs ventrolateral sides yellow in the latter).