Limnonectes nguyenorum Kurlbaum & Hoang, 2015, sp. nov.
Creators: name: Kurlbaum, Scuyler
name: Hoang, Ngoc Van
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Amphibia
Anura
Dicroglossidae
Limnonectes
Limnonectes nguyenorum

description: Limnonectes nguyenorum sp. nov.
Holotype. Adult male VNMN A.2015.1 (TAO 697; GenBank: HM067250; Fig. 2 A–F), from Cao Bo Commune, Vi Xuyen District, Ha Giang Province, Vietnam at 22°46'27"N, 104°52'01"E, 900 m, collected on 0 3 May 2009 by Nguyen Thien Tao and Hoang Van Ngoc, and deposited at the Vietnam National Museum of Nature (Hanoi, Vietnam).
Paratypes. Three paratypes collected from Ha Giang Province, Vietnam. One adult male IEBR A.2015.3 (TNE 02; GenBank: HM067258), from Vang Pheng Stream, Cao Bo Commune, Vi Xuyen District at 22°46'16"N, 104°51'56.6"E, 909 m, collected on 5 May 2008 by Ngoc V. Hoang and deposited at the Institute for Ecology and Biological Resources. Two adult females: AMNH A- 163944 (GenBank: HM067267), collected from Bac Trao Stream, Cao Bo Commune, Vi Xuyen District at 22°45' 39"N, 104°52' 23", 600 m, collected on 24 May 2000 by Truong Q. Nguyen and Raoul Bain, deposited in the American Museum of Natural History; and VNMN A.2015.3 (TAO 699; GenBank: HM067252), from Vang Pheng Stream, Cao Bo Commune, Vi Xuyen District, at 22°46' 27"N, 104°52' 01"E, 900m, collected with the holotype on 0 3 May 2009 by Nguyen Thien Tao and Hoang Van Ngoc and deposited in the Vietnam National Museum of Nature (Hanoi, Vietnam).
Diagnosis. Limnonectes nguyenorum is considered a member of Limnonectes on the basis of molecular evidence (McLeod 2010; McLeod et al. 2012) and the presence of fanglike odontoid processes on the lower jaw, a sexually dimorphic feature; larger in males than females (Emerson et al. 2000). Additionally, these specimens are part of the L. kuhlii Complex on the basis of molecular data (McLeod2010; McLeod et al. 2012), and possession of an indistinct (or hidden) tympanum and fully webbed toes, both of which are characters traditionally used to diagnose L. kuhlii sensu lato from its congeners (Boulenger 1920; Duméril & Bibron 1841; Inger 1966; Taylor 1962; Tschudi 1838).
Limnonectes nguyenorum can be distinguished from all other members of the kuhlii Complex, by the following combination of characters: (1) adult male SVL 43.5–43.8 mm (mean = 43.7; SD ± 0.2; n = 2), adult female SVL 36.5–43.6 mm (mean = 40.0; SD ± 5.0; n = 2); (2) males with nuptial pads on first and second fingers (Finger II & III); (3) males with slightly enlarged heads (HL 42–43% of SVL; 39.2–39.4% in females); (4) head longer than wide in both males and females (HL 105–112% HW in males; 107–116% in females); (5) canthus rostralis indistinct and rounded, lores flat; (6) indistinct supratympanic fold; (7) prominent white bar extending from nares to insertion of arm, upper lip with distinct white spots and dark brown bars; (8) skin on top of head and venter smooth, skin on dorsum and flanks very feebly crenulate; (9) pericloacal area, and dorsal surfaces of shank and foot covered with heterogeneous tubercles; (10) relative finger length (longest to shortest) when adpressed: IV–V–III– II.
Description of holotype. Adult male. Habitus slender, head slightly enlarged (HL 43% SVL); head longer than wide (HL 105% HW). Rostrum bluntly pointed in dorsal view, projecting beyond lower jaw, dorsoventrally flattened in profile; nostril dorsolaterally oriented (nearly dorsal), closer to tip of snout than to eye; internarial distance subequal to interorbital distance (IN 99% IO); canthus rostralis indistinct and rounded; lores flat; upper lip flat and smooth, not reaching post-rictal tubercle (small tubercle just posterior to corner of mouth); eye diameter 22% head length; upper eyelid width less than interorbital distance (UEW 76% IO). Tympanic annulus not visible through skin; lacks supratympanic fold. Vomerine teeth on oblique ridges, separated from each other by less than width of one ridge. Choanae oval, perpendicular to longitudinal axis of body. Odontoid processes robust with rounded tips, angled posteriorly; length more than twice depth of mandible at base of processes. Prominent symphysial knob at mandibular symphysis. Tongue oval; deep posterior U-shaped notch.
Finger tips rounded, not expanded into discs, with rounded distal pad; decreasing lengths of fingers: IV–V–III– II; no webbing between fingers; digits indicated by Roman numeral (tubercle count in parentheses): V (2), IV (2) III (1), II (1); proximal subarticular tubercles prominent, round, and elevated; distal subarticular tubercles prominent, round, and elevated on fingers IV and V; thenar metacarpal tubercle large, oval, slightly elevated; inner metacarpal tubercle round and slightly elevated, smaller than thenar and outer tubercles, contact only between inner and outer tubercles; outer metacarpal tubercle subequal in size to inner tubercle, laterally compressed oval, not elevated. Prominent nuptial pads composed of minute spines on Fingers II and III; present on dorsal, pre- and post-axial surfaces of Finger II from the behind the carpometacarpal joint to the tip of distal phalanx, covering most of the thenar tubercle; present on the dorsal, pre-and post-axial surfaces of Finger III extending to only the distal end of the penultimate phalanx. Tips of toes rounded, not expanded into discs, toe pads elevated; decreasing lengths of toes: IV–III–V–II–I; toes webbed to middle of terminal phalanx (webbing formula = I 0+–0+ II 0+–0+ III 0+– 0+ IV 0+–0+ V); raised, but not movable dermal ridge on postaxial side of Toe V from middle of terminal phalanx to proximal end of metatarsus; distinct, movable flap of skin on pre-axial side of Toe I from middle of terminal phalanx to level of inner metatarsal tubercle, continuing on distal two thirds of tarsus; proximal subarticular tubercles prominent, elevated, round; distal subarticular tubercles are round but low and indistinct; digits indicated by roman numeral (tubercle count in parentheses): V (2), IV (3) III (2), II (1), I (1) inner metatarsal tubercle oval, elongate with elevated postaxial edge.
In preserved specimen, skin on throat, dorsal surfaces of forelimb, thigh, and dorsum feebly crenulate; skin on sides dotted with translucent spinules; pericloacal area, dorsal surfaces of shank and foot covered with small heterogeneous sized tubercles tipped with translucent spinules; tubercles on shank arranged in rows radiating from tibiotarsal articulation; skin on head and venter smooth.
Color in preservative light brown dorsum, distinct dark brown dorsolateral patches posterosuperior to axila, dark brown inverted chevron at level of shoulders, pair of dark brown blotches on either side of body axis at level of mid-back; broad, dark brown interorbital bar extending to lateral margins of upper eyelids and separated by a light brown horizontal stripe; dark brown bar extending from tip of snout through midline of eye, continuing to insertion of arm; upper lip dark brown with irregularly spaced light brown patches; distinct white spots on tip of snout, upper lip, lores, and inferior margin of eye; lower lip dark brown with indistinct light brown bars; dark brown crossbars on dorsal surface of limbs from groin to foot and axilla to hand, posterior thigh mottled; throat mottled; venter immaculate, ventral portions of thighs and legs heavily mottled; palmar and plantar surfaces dark brown, webbing between toes mottled.
Measurements. Morphometric data (in mm) for the holotype (male, VNMN A.2015.1) are: SVL = 43.8; ED = 4.2; EN = 3.6; ES = 6.8; FEL = 18.7; FOL = 25.3; HL = 18.8; HW = 17.9; IN = 3.4; IO = 3.4; LAL = 7.7; MN = 16.4; PAL = 10.1; TBL = 20.3; UEW = 2.6; OL = 2.5; MD = 1.2.
Variation. Variation in body proportions given in Table 1. Because of the small sample size available for examination (2 males, 2 females), statistical tests could not be applied to measurement data. All adult males have nuptial pads. Both female specimens were found to be gravid with mature ova (Fig. 2 G). One female specimen (VNMN A.2015.3) was dissected and found to have a clutch size of approximately 100 ova with an average diameter of 0.67 mm (based on measurements of 21 ova). Relative head length (HL/SVL) is only slightly greater in males (42–43%) than in females (39%). Based on the available data, it seems that sexually mature males and females are nearly equal in size (max male SVL = 43.81, max female SVL = 43.55). Distal subarticular tubercles are more prominent in female paratype than in holotype (possibly an artifact of preservation).
Etymology. The specific name, nguyenorum, is the plural possessive form of the family name Nguyen. This species is named in honor of two herpetologists who have contributed greatly to our understanding of Vietnamese herpetology and biodiversity, Truong Quang Nguyen and Tao Thien Nguyen. It is rare to find siblings working together in herpetological research, and more so to find brothers as productive as these. We commend them for their efforts and recognize that without them this and many other amphibians and reptiles in Vietnam would remain undescribed.
Comparisons. As noted previously, there is a great deal of morphological similarity among the frogs of the genus Limnonectes, and in particular, within the L. kuhlii Complex (Emerson et al. 2000; McLeod 2008, 2010; McLeod et al. 2011, 2012). Based the phylogenetic hypothesis presented here and elsewhere (McLeod 2008, 2010; McLeod et al. 2011, 2012) in which true L. kuhlii is restricted to the island of Java, we have elected to limit morphological comparisons to those taxa to which it is (1) most closely related (Fig. 1), and (2) geographically proximate. Comparisons are presented below.
The most notable difference between Limnonectes nguyenorum and all other known members of the L. kuhlii complex is its diminutive size. Based on combined male-female SVL (41.8 mm), Limnonectes nguyenorum is the smallest known member of the L. kuhlii complex (size class 1). It is considerably smaller than all other members of the Indochinese clade to which it belongs: Limnonectes megastomias (class 4, mean SVL = 77.2 mm, McLeod et al. 2012), L. isanensis (class 3, 65.3 mm, McLeod et al. 2012), L. taylori (class 2, 57.7 mm, McLeod et al. 2012), and L. jarujini (presumably class 4, males = 73.3 mm, females = 62.0 mm, Matsui et al. 2010b). Similarly, the new species differs L. bannaensis (class 3, 60.4 mm, n = 64). It is worth noting that the mean SVL for specimens of L. bannaensis collected at the same site as the new species is slightly smaller (class 2, 54.6 mm, n=18) than the entire series examined the 54.6 mm (31.3–86.6 mm, n =18).
Based on current understanding of systematics, taxonomy, and species distributions in Indochina, L. nguyenorum and L. bannaensis are the only sympatric species of the L. kuhlii Complex in Vietnam. The only other geographically proximate and closely related taxon with which L. nguyenorum could be confused based on size and general appearance is Limnonectes taylori, which is known from northwestern Thailand, northwestern Laos, and eastern Myanmar (McLeod 2010 as “Lineage 12”, Matsui 2010b). Comparisons of uncorrected pair-wise distance data were consistent with the results of other recent studies of the L. kuhlii complex where intraspecific differences are small (L. nguyenorum = 0.24%) and interspecific distances are considerably larger, ranging from 6.5% to 16.9% (McLeod 2010, McLeod et al. 2012). All remaining comparisons of the new species are thus restricted to L. taylori and L. bannaensis, the latter of which it is syntopic with (but not most closely related).
A noteworthy difference in the new species is the similar SVL of males and females (both males and one female slightly larger than 43.5 mm, the other female 36.5 mm). This stands in contrast to a general assumption that among the “fanged frogs” males are larger than females (Emerson et al. 2000). This pattern is exemplified by several species, including L. taylori where males are, on average considerably larger (61.3 mm) than females (53.0 mm). Interestingly, in this study, the opposite is also true of L. bannensis, where the females sampled are, on average, larger (62.0 mm) than males (59.5 mm), but male maximum size still slightly exceeds that of females (90.8 and 87.4 mm, respectively; Table 2).
See text for character definitions. Presence (0) or absence (1) of a tympanum visible through the overlying skin is indicated. Measurements of tympanum diameter (TD) only taken if visible tympanum was present.
* Holotype
SVL-HL/SVL 0.57–0.58 0.61–0.61 0.51–0.63 0.49–0.65 0.47–0.60 0.54–0.63
......continued on the next page Size and pattern of tubercules on the leg and foot are visibly different and seem to be one of the most reliable characters for distinguishing species one from another within this complex. Among the three species being compared here, L. taylori has the largest (relatively) and most closely clustered tubercles giving the leg a rough appearance, L. nguyenorum having slightly smaller and heterogeneously sized tubercles, and L. bannaensis has still smaller and homogenously sized tubercles giving the leg a relatively smooth appearance (Fig. 2 F & I).
Coloration is another character that appears to facilitate easy identification of species however this study is limited to describing color from preserved specimens. In preservative, the four specimens of L. nguyenorum are lighter colored than either L. bannaensis or L. taylori (even in juvenile examples). Prominent white spots on the upper lip, and the light brown bar passing from snout to insertion of the arm in L. nguyenorum distinguish it from L. bannaensis which is uniformly darker colored and has fewer small faint spots visible. The interorbital bar extends farther posteriorly in L. nguyenorum than in L. bannaensis. The new species has more mottling on the chin and ventral surface of the hind limbs than L. taylori and L. bannensis. Both L. nguyenorum and L. taylori have immaculate venters whereas the venter of L. bannaensis is mottled.
The new species appears to have smaller hands (PAL) relative to SVL (♂ = 22%, ♀= 20%) than either L. bannaensis or L. taylori, for which hands of both sexes and both species are 24% of SVL. Limnonectes nguyenorum also appears to have relatively short hind limbs (FOL) relative to SVL (♂ = 61%, ♀ = 62%) when compared to L. taylori (♂ = 64%, ♀ = 63%) and L. bannensis (67% both sexes). In L. nguyenorum the nares are slightly more dorsally oriented and the internarial distance is small relative to the eye–nostril distance (EN/IN: ♂=109%, ♀=114%) than in either L. bannenensis or L. taylori where EN/IN is nearly equal (Table 2). Between L. nguyenorum and L bannaensis, head shapes differ subtly, but reliably, with L. nguyenorum having a slightly more rounded snout in lateral perspective and L. bannaensis having a relatively blunt snout that extends slightly beyond, and slopes towards the lower jaw. Both males in our sample have nuptial pads on the first and second fingers, but most male L. bannaensis (30 of 39) and L. taylori (10 of 13) have nuptial pads only on the first finger. Relative finger length is consistent in the new species (IV–V–III–II), but shows slight variation in both sexes of L. bannaensis and L. taylori where Finger II may be longer than, or equal to, Finger III.
Distribution and ecology. Based on the specimens examined, Limnonectes nguyenorum is only known from Vi Xuyen District in northwestern Ha Giang Province, northern Vietnam (Fig. 3). As with other members of the L. kuhii Complex, L. nguyenorum is found along streams in submontane evergreen forests (Fig. 4). The new species seems to occur at elevations approximately between 600 and 900 m, corresponding generally to the transition between lowland and montane forests. Based upon the presence of gravid females of both L. nguyenorum and L. bannaensis during collecting events, it is possible that these species breed at similar times and under similar conditions.
description: Published as part of Kurlbaum, Scuyler & Hoang, Ngoc Van, 2015, More of the same: a diminutive new species of the Limnonectes kuhlii complex from northern Vietnam (Anura: Dicroglossidae), pp. 201-214 in Zootaxa 3947 (2) on pages 203-209, DOI: 10.11646/zootaxa.3947.2.4, http://zenodo.org/record/245728