2004

Asiatic Herpetological ResearchVol. 10, pp. 17-21

A New Philautus (Amphibia: Rhacophoridae) from Northern Laos
BRYAN L. STUART1,2,3,* AND HAROLD F. HEATWOLE4
1Field Museum of Natural History, Department of Zoology, Division of Amphibians & Reptiles,

1400 S. Lake Shore Drive, Chicago, Illinois, USA 60605-2496;*Corresponding author: E-mail: bstuart@fieldmuseum.org
2University of Illinois at Chicago, Department of Biological Sciences, 845 W. Taylor,Chicago, Illinois, USA 60607-7060
3Wildlife Conservation Society, P.O. Box 6712, Vientiane, Laos
4North Carolina State University, Department of Zoology, P.O. Box 7617, Raleigh,North Carolina, USA 27695-7617; E-mail: harold_heatwole@ncsu.edu
Abstract. - A new Philautus is described from Phou Dendin National Biodiversity Conservation Area in northern
Laos. Philautus petilus sp. nov. is most remarkable by having a very slender, elongate habitus. Other distinguishing
characteristics include having a tympanum diameter 80% of the eye diameter, white asperities on the dorsum, anddistinctive coloration consisting of a soft yellow-beige dorsolateral surface with broken black stripes posteriorly, alavender wash on dorsal surface of limbs, upper lip, and sides, a black stripe below edge of canthus extending fromsnout tip to flanks near level of mid-body, and a black spot equal in diameter to the tympanum located just anterior
to the inguinal region.
Key words. - Laos, new species, Philautus, Rhacophoridae.

Introduction
Bourret (1942) remains the major work on the amphibians of Laos, supplemented only recently by descriptions of new species (Inger and Kottelat 1998; Stuart andPapenfuss 2002). Consequently, the amphibian fauna of
Laos is imperfectly known.
From 6-26 October 1999, we conducted a herpetofaunal survey of Phou Dendin National Biodiversity
Conservation Area in eastern Phongsaly Province,
northern Laos, near to the tri-border area of Laos,
Vietnam, and China (Figure 1A). The area surveyed wasmostly covered in hilly evergreen forest, sometimes
mixed with stands of natural bamboo, with small, rocky
streams flowing down hillsides into the larger, swift
Nam Ou and Nam Khang Rivers, at elevations from600-1000 m. During the course of that work we found asingle, adult female specimen of an enigmatic, rhacophorid treefrog, which we describe here as a newspecies of Philautus.

Materials and Methods
The single specimen found was caught in the field byhand, preserved in 10% buffered formalin, and latertransferred to 70% ethanol. A tissue sample was taken by
preserving pieces of liver in 95% ethanol before thespecimen was fixed in formalin. The specimen was© 2004 by Asiatic Herpetological Researchdeposited at the Field Museum of Natural History(FMNH).
Measurements largely follow those of Bain et al.
(2003) and were made with dial calipers to the nearest
0.1 mm. Abbreviations used are: SVL = snout-vent
length; HDL = head length from tip of snout to the commisure of the jaws; HDW = head width at the commisureof the jaws; SNT = snout length from tip of snout to theanterior corner of the eye; EYE = eye diameter; IOD =interorbital distance; TMP = horizontal diameter of tympanum; TEY = tympanum-eye distance from anterioredge of tympanum to posterior corner of the eye; FPL =length of finger III disk from the base of the pad to its
tip; FPW = width of finger III disc at the widest part ofthe pad; TPL = length of toe IV disk; TPW = width of
toe IV disk. Measurement ratios are reported as percentages (%) rounded to the nearest integer.
Philautus petilus, new species(Figure 1B)
Material examined. -Holotype: FMNH 257902, adultfemale, collected by the authors on 23 October 1999 inPhou Dendin National Biodiversity Conservation Area,Phongsaly District, Phongsaly Province, Laos,
22°05’44”N 102°08’10”E, at 600 m elevation.
Diagnosis. - An elongate, slender Philautus having ahead width only 27% of SVL; tympanum diameter 80%

Vol. 10, p. 18

Asiatic Herpetological Research

2004

Figure 1A-C. A. Map showing the type locality (black dot) of Philautus petilus sp. nov. in Phongsaly Province, northern Laos. B. The adult female holotype (FMNH 257902) of Philautus petilus sp. nov., anesthetized prior to preservation. Photograph by Bryan L. Stuart. C. The hand of the adult female holotype (FMNH 257902) of Philautus petilus
sp. nov. in preservation. Photograph by Nikolai L. Orlov.
of eye diameter; white asperities on head, eyelids, back,dorsal surface of tibia and forelimbs, and anterior half ofsides; no fringes, row of enlarged tubercles, or accessory flaps of skin on outer margins of limbs; black stripe
below edge of canthus extending from tip of snout toflanks near level of mid-body; black spot slightly anterior to inguinal region, equal in diameter to the tympanum.
Description of Holotype. - Habitus elongate, slender;head width 27% of SVL; head slightly longer than wide;snout obtusely pointed in dorsal view, projecting beyondlower jaw, round in profile, not depressed; nostril lateral, near tip of snout; canthus rounded but distinct, constricted behind nostrils; lores slightly concave, oblique;eye diameter less than snout length, interorbital distancewider than upper eyelid; tympanum visible, notdepressed relative to skin of temporal region, tympanic
rim slightly elevated relative to tympanum, tympanum
diameter 80% of eye diameter; weak supratympanic foldfrom eye to shoulder; vomerine teeth very small, inoblique rows closer to choanae than to each other;
tongue deeply notched posteriorly.
Tips of all four fingers expanded, about two times
the width of phalanges, with circummarginal grooves,width of finger I disc 60% the width of finger III disc,width of finger III disc 71% the diameter of tympanum;
relative finger lengths I < II < IV < III; webbing absent;
fingers III and IV with large middle subarticular tuber-cle and smaller palmar tubercle at base; fingers I and IIwith large palmar tubercle at base.
Tips of toes expanded, width of toe IV disc slightlysmaller than width of finger III disc; toe V longer thantoe III; toe I webbing to midway between subarticular
tubercle and disc, continuing only as narrow fringe todisc; toes II, III, and IV webbing to distal subarticular
tubercle, continuing only as narrow fringe to disc; toe V
webbing to midway between distal subarticular tubercle
and base of disc, continuing only as narrow fringe tobase of disc; inner metatarsal tubercle elongated, outer
metatarsal tubercle very small, almost inconspicuous.
Skin on dorsal and ventral surfaces smooth, except
for distinct, white asperities on head, eyelids, back, dorsal surface of tibia and forelimbs, and anterior half ofsides; no fringes, row of enlarged tubercles, or accessory flaps of skin on outer margins of limbs.
Left ovary with fewer than 25, developing, creamywhite ova (color in preservative).
In life, top of head and back light brown with darkbrown reticulations and scattered black spotting; dorsolateral surface of head and body soft yellow-beige, withshort, broken black stripe on dorsolateral surface fromlevel of midbody extending toward groin; lavender washon dorsal surface of limbs, upper lip, and sides; black
stripe below edge of canthus extending from tip of snout
to anterior border of eye, and from posterior border ofeye along supratympanic fold to flanks near level of
mid-body; black spot slightly anterior to inguinal region,

2004

Asiatic Herpetological Researchequal in diameter to the tympanum; black ‘M’-shaped
marking over anus; black spot on tarsus closer to articulation than foot, narrow black crossbars on hindlimbs,
some black flecking on forelimbs; venter creamy-white,dark spotting on chin and throat, pigmentation on underside of hands, feet, and tibiotarsus. In preservative, yellow-beige and lavender coloration lost.
Measurements (mm) of holotype. - SVL 33.8; HDL
9.9; HDW 9.2; SNT 4.1; EYE 3.0; IOD 2.3; TMP 2.4;
TEY 1.5; FPL 1.5; FPW 1.7; TPL 1.3; TPW 1.4.
Comparisons. - The generic assignments of small, rhacophorid (or rhacophorine) treefrogs are uncertain anddebated (Bossuyt & Dubois 2001; Wilkinson et al.
2002). Therefore, we compare P. petilus with all otherspecies of small to medium-sized rhacophorid (or rhacophorine) treefrogs having reduced finger webbing thatare reported from the vicinity of northern Laos, regardless of what genus they are currently referred to. These
include Chirixalus doriae Boulenger, C. hansenae(Cochran), C. laevis (Smith), C. nongkhorensis(Cochran), C. palpebralis (Smith), C. vittatus(Boulenger), Philautus abditus Inger, Orlov, &Darevsky, P. albopunctatus Liu & Hu, P. banaensis
Bourret, P. carinensis (Boulenger), P. gracilipes
Bourret, P. gryllus Smith, P. jinxiuensis Hu, P. longchuanensis Yang & Li, P. maosonensis Bourret, P. menglaensis Kou, P. ocellatus Liu and Hu, P. odontotarsus Ye andFei, P. parvulus (Boulenger), P. rhododiscus Liu and Hu,
Rhacophorus appendiculatus (Günther), R. baliogaster
Inger, Orlov & Darevsky, R. bisacculus Taylor, R. verrucosus Boulenger, Theloderma asperum (Boulenger), andT. stellatum Taylor (Bourret 1942; Taylor 1962; Inger etal. 1999; Fei 1999; Orlov et al. 2002).
Philautus petilus differs from all species ofChirixalus Boulenger by lacking the two outer fingers
appearing to be opposable to the two inner ones (presentin Chirixalus). Philautus petilus further differs from C.
doriae and C. nongkhorensis by lacking outer finger
webbing (outer fingers 1/3 webbed in doriae andnongkhorensis), from C. hansenae, C. laevis and C. vittatus by lacking light-colored dorsolateral stripes (present in hansenae, laevis and vittatus), and from C. palpebralis by lacking a yellow streak from below eye toshoulder (present in palpebralis). Philautus petilus differs from P. abditus by having a visible tympanum (hidden in abditus) and lacking large black spots on the legs(present in abditus). Philautus petilus differs from P.
albopunctatus by having dorsal asperities (absent inalbopunctatus) and lacking white blotches on the snout,
dorsum and above anus (present in albopunctatus).
Philautus petilus differs from P. carinensis by having
the snout longer than the eye diameter (snout shorter

Vol. 10, p. 19

than eye diameter in carinensis) and by having a slender
habitus (stocky habitus in carinensis). Philautus petilus
differs from P. gracilipes by having a head width 27% of
SVL (head width 45% of SVL in gracilipes), having thewidth of finger III disc 71% the diameter of tympanum(width of finger III disc equal to the diameter of tympanum in gracilipes), and lacking mostly green coloration
with dark-brown eyelids (present in gracilipes).
Philautus petilus differs from P. jinxiuensis by lacking alarge interorbital dark blotch extending posteriorly into
two broad, dark dorsolateral stripes (present in jinxiuensis). Philautus petilus differs from P. longchuanensis byhaving a tympanum diameter larger than width of finger
III disc (tympanum diameter smaller than width of finger III disc in longchuanensis). Philautus petilus differsfrom P. maosonensis by having the head slightly longer
than wide (head wider than long in maosonensis), by
having the snout projecting beyond the lower jaw (snoutnot projecting beyond lower jaw in maosonensis), by
having the tympanum diameter 80% of eye diameter(tympanum diameter approximately 2/3 eye diameter inmaosonensis), and by lacking a thin band between theeyelids, a large dark marking on the back, and a dark
spot behind the axilla (present in maosonensis).
Philautus petilus differs from P. menglaensis by havingsmooth skin with asperities on the dorsum (warty skinon dorsum in menglaensis) and by having a tympanum
diameter larger than the width of finger III disc (tympanum diameter smaller than or equal to width of finger III
disc in menglaensis). Philautus petilus differs from P.
ocellatus by lacking a round black blotch on the occiput(present in ocellatus). Philautus petilus differs from P.
parvulus by having the snout longer than the eye diameter (snout shorter than eye diameter in parvulus), having a visible tympanum (hidden in parvulus), and having
the nostril close to the tip of snout (nostril midway
between eye and tip of snout in parvulus). Philautus
petilus differs from P. rhododiscus by lacking darkbrown coloration with black spots, grayish-white ventral
marbling, and reddish-orange finger and toe discs (present in rhododiscus). Philautus petilus differs from P.
banaensis, P. gryllus, P. odontotarsus, R. appendiculatus, R. bisacculus, and R. verrucosus by lacking dermal
fringes or tubercles on the limbs (present in banaensis,gryllus, odontotarsus, appendiculatus, bisacculus, andverrucosus). Philautus petilus differs from all species of
Theloderma Tschudi by having smooth skin with dorsal
asperities (skin rugose in Theloderma).
Etymology. - The species name petilus (L.) means slender, referring to the distinct habitus of the holotype.
Ecology. - The holotype was collected at 2215 h on abamboo leaf 1 m above the ground in hilly evergreen

Vol. 10, p. 20

Asiatic Herpetological Research

forest mixed with bamboo, approximately 200 m fromthe bank of the Nam Ou River, at 600 m elevation.
Remarks. - The generic assignments of small, rhacophorid (or rhacophorine) treefrogs are uncertain,debated, and likely to be considerably revised in the near
future (Bossuyt & Dubois 2001; Wilkinson et al. 2002).
Many species have been moved among the genera
Chirixalus Boulenger and Philautus Gistel (Frost 2002).
Philautus petilus does not have the two outer fingers
appearing to be opposable to the two inner ones (Figure1C), which is diagnostic of the genus Chirixalus (Liem1970). Historically, Philautus was diagnosed by theabsence of vomerine teeth (Leim 1970; Bossuyt andDubois 2001), but this character is known to vary within a species, and consequently Liem (1970) included
species in the genus Philautus that sometimes havevomerine teeth. Philautus petilus has very small vomerine teeth. Bossuyt and Dubois (2001) proposed that only
species having direct aerial development (lacking a freeswimming aquatic tadpole) be included in the genus
Philautus. The mode of reproduction in P. petilus isunknown, but it does have a small clutch size (the leftovary of the holotype holds fewer than 25 ova). Dring(1987) reported total clutch sizes of only 2-26 eggs infive species of Philautus, including the type species, P.
aurifasciatus. In the absence of a phylogeny and more
substantial reproductive data, we recognize that ourplacement of petilus into the genus Philautus is tentative.

Acknowledgments
The opportunity to work in Laos was made possible by
the Wildlife Conservation Society / Division of Forest
Resource Conservation Cooperative Program. The
Ministry of Agriculture and Forestry (Vientiane, Laos)permitted export of specimens to the Field Museum ofNatural History. Bee Thaovanseng assisted with fieldwork in Laos. Financial support was provided by The
John D. and Catherine T. MacArthur Foundation (withHarold Voris and Robert Inger), the National
Geographic Society (Grant no. 6247-98), and theWildlife Conservation Society. Harold Voris, Alan
Resetar, Jamie Ladonski, and Jennifer Mui facilitatedexamining specimens at the Field Museum of NaturalHistory. Sophie Molia translated French descriptionsand Tan Fui Lian translated Chinese descriptions. Robert
Inger, Nikolai Orlov, and Jeff Wilkinson shared theirtaxonomic opinions on the specimen. Nikolai Orlov
photographed the preserved specimen. Robert Inger,Raoul Bain, and an anonymous reviewer improved themanuscript.

2004

Literature Cited
Bain, R. H., A. Lathrop, R. W. Murphy, N. L. Orlov, andHo Thu Cuc. 2003. Cryptic species of a cascadefrog from Southeast Asia: taxonomic revisions anddescriptions of six new species. American Museum
Novitates 3417:1-60.
Bossuyt, F. and A. Dubois. 2001. A review of the frog
genus Philautus Gistel, 1848 (Amphibia, Anura,Ranidae, Rhacophorinae). Zeylanica 6(1):1-112.
Bourret, R. 1942. Les batraciens de l’Indochine.
Mémoires de l’Institut Océanographique del’Indochine 6:1-547.
Dring, J. 1987. Bornean treefrogs of the genus Philautus(Rhacophoridae). Amphibia-Reptilia 8(1987):1947.
Fei, L. 1999. Atlas of Amphibians of China. Zhengzhou:
Henan Publishing House of Science andTechnology. 432 pages. [in Chinese].
Frost, D. R. 2002. Amphibian Species of the World: anonline reference. Version 2.21 (15 July 2002).
Electronicdatabaseavailableat
http://research.amnh.org/herpetology/amphibia/index.html.
Inger, R. F. and M. Kottelat. 1998. A new species ofranid frog from Laos. The Raffles Bulletin of
Zoology 46(1):29-34.
Inger, R. F., N. Orlov & I. Darevsky. 1999. Frogs ofVietnam: a report on new collections. Fieldiana,
Zoology New Series, 92:1-46.
Liem, S. S. 1970. The morphology, systematics, andevolution of the Old World treefrogs(Rhacophoridae and Hyperoliidae). Fieldiana
Zoology 57:1-145.
Orlov, N. L., R. W. Murphy, N. B. Ananjeva, S. A.
Ryabov, & Ho Thu Cuc. 2002. Herpetofauna ofVietnam, a checklist. Part I. Amphibia. Russian
Journal of Herpetology 9(2):81-104.
Stuart, B. L. and T. J. Papenfuss. 2002. A new salamander of the genus Paramesotriton (Caudata:Salamandridae) from Laos. Journal of Herpetology
36(2):145-148.

2004

Asiatic Herpetological Research

Taylor, E. H. 1962. The amphibian fauna of Thailand.
University of Kansas Science Bulletin 63(8): 265599.
Wilkinson, J. A., R. C. Drewes, and O. L. Tatum. 2002.
A molecular phylogenetic analysis of the family
Rhacophoridae with an emphasis on the Asian andAfrican genera. Molecular Phylogenetics andEvolution 24: 265-273.

Vol. 10, p. 21