Platypelis ravus, Glaw & Köhler & Vences, 2012

Glaw, Frank, Köhler, Jörn & Vences, Miguel, 2012, A tiny new species of Platypelis from the Marojejy National Park in northeastern Madagascar (Amphibia: Microhylidae), European Journal of Taxonomy 9, pp. 1-9 : 3-7

Platypelis ravus sp. nov.

Remark

This species has been referred to as Platypelis sp. (Marojejy) by Vences et al. (2006), as Platypelis sp. aff. mavomavo 2 by Glaw & Vences (2007), as Platypelis sp. 2 by Wollenberg et al. (2008) and as Platypelis sp. 4 by Vieites et al. (2009).

Etymology

The specific epithet is an adjective derived from Latin ravus = grayish-yellow, referring to the diagnostic ventral colour of the species.

Holotype

ZSM 349/2005 (field number FGZC 2813), adult ♂, collected at Marojejy National Park , ‘ Camp Simpona’, 14°26.199'S 49°44.601'E, 1326 m above sea level, Antsiranana Province, northeastern Madagascar, on 15 Feb. 2005 by F. Glaw, M. Vences, and R.D. Randrianiaina.

Paratypes

ZSM 350/2005 (field number FGZC 2823) and ZSM 351/2005 (FGZC 2824), two adult ♂ - ♂, with same data as holotype, except that ZSM 351/2005 was collected on 16 Feb. 2005. Three additional paratypes, all ♂ - ♂ collected while calling, were deposited in the UADBA collection (still uncatalogued) and are labelled with the field numbers FGZC 2822, 2825 and 2869. Their collection data are the same as in the holotype except for FGZC 2869 (collected on 16 May 2005).

Diagnosis

The new species is assigned to the genus Platypelis based on enlarged terminal finger discs, absence of prepollex, and molecular phylogenetic relationships ( Wollenberg et al. 2008). It differs from other arboreal cophyline microhylids of the genus Anodonthyla by the absence of a prepollex in males, and from Plethodontohyla with enlarged finger and toe discs [ P. guentheri Glaw & Vences, 2007 , P. inguinalis Boulenger, 1882 , P. mihanika Vences, Raxworthy, Nussbaum & Glaw, 2003 , P. notosticta (Günther, 1877) ] by much smaller size (SVL 17-19 mm vs. 26-100 mm). Within the Platypelis / Cophyla clade, the species is distinguished from Cophyla berara Vences, Andreone & Glaw, 2005 , C. phyllodactyla Boettger, 1880 , Platypelis alticola (Guibé, 1974) , P. cowanii Boulenger, 1882 , P. grandis (Boulenger, 1889) , P. mavomavo Andreone, Fenolio & Walvoord, 2003 , P. milloti Guibé, 1950 , P. pollicaris Boulenger, 1888 , P. tsaratananaensis Guibé, 1974 , and P. tuberifera (Methuen, 1920) by distinctly smaller size (SVL of adult males 17-19 mm vs. 23-88 mm), and from P. tetra Andreone, Fenolio & Walvoord, 2003 by presence of a regular pattern of moderately-sized tubercles on the back (vs. four symmetrically arranged and distinctly enlarged white tubercles), a third toe of the same length than the fifth (vs. toe three longer than toe five), by presence of yellow ventral colouration (vs. absence), and by a much higher note repetition rate of the advertisement calls. It differs from Cophyla occultans (Glaw & Vences, 1992) by smaller size (SVL 17-19 mm vs. 18-21 mm), and equal length of toe 3 and 5 (vs. toe 3 <5). It is distinguished from Platypelis barbouri Noble, 1940 (and most likely from its junior synonym Paracophyla tuberculata Millot & Guibé, 1951 , described from the well sampled type locality Andasibe) by absence of red colour on the ventral side of the hindlimbs and belly, and a largely smooth dorsal surface (vs. strongly tuberculate).

Summarizing, the new species is most similar to P. barbouri (the only other Platypelis without vomerine teeth and in addition with a rather similar advertisement call, but with reddish instead of yellow ventral surface, and more strongly expressed and irregularly arranged tubercles on dorsal surface), and to P. mavomavo (with yellow ventral surface but distinctly larger SVL). It differs, however, from these and all other nominal species of Platypelis and Cophyla (except P. cowanii for which no genetic data is available) by a high genetic divergence (see Wollenberg et al. 2008; Vieites et al. 2009 and unpublished data for P. alticola , P. tsaratananaensis , P. tetra and Cophyla occultans ). Phylogenetically, it appears to be sister to P. milloti (see below) which however is larger, has a much more contrasting dorsal pattern, red colour ventrally, and a much faster note repetition rate in advertisement calls (106/min vs. 18-19/ min).

Description of the holotype

Specimen in good state of preservation, some muscle tissue removed from right thigh, snout-vent length 19.1 mm. Body slender; head as wide as long, not wider than body; snout bluntly rounded in dorsal and lateral views; nostrils directed dorsolaterally, not protuberant, nearer to tip of snout than to eye; canthus rostralis indistinct, very slightly concave; loreal region plain; tympanum moderately distinct, 56% of eye diameter; supratympanic fold moderately distinct, straight; tongue ovoid, not bifid or notched; weakly expressed maxillary teeth present; vomerine teeth absent; choanae rounded. Forelimbs slender; subarticular tubercles single, flat, and hardly recognizable; outer metacarpal tubercle probably large and flat, but very difficult to recognize; inner metacarpal tubercle large, forming distinct protuberance at base of first finger; hand with traces of webbing only between fingers 3 and 4; fingers distinctly flattened and relatively broad along entire length; relative length of fingers 1 <2 <4 <3, fourth finger distinctly longer than second; finger discs distinctly enlarged, slightly triangular; nuptial pads absent. Hindlimbs slender; tibiotarsal articulation reaching tympanum when hindlimb adpressed along body; tibia length, 39% of SVL; lateral metatarsalia strongly connected; inner metatarsal tubercle small and flat, difficult to recognize; outer metatarsal tubercle absent; webbing between toes weakly developed, with traces of web between second and third toe, and some webbing between third and fouth, and fourth and fifth toe; webbing formula difficult to assess because subarticular tubercles on toes are hardly recognizable; toes flattened and relatively broad along their entire length; relative length of toes 1 <2 <3 = 5 <4; third toe of similar length as fifth. Dorsal skin smooth, without dorsolateral folds. Ventral skin slightly granular on throat, smooth on chest and moderately granular on belly.

After five years in 70% ethanol, dorsum light brown with distinct and well-delimited symmetrical dark brown markings: a heart-shaped marking starting between eyes and extending on posterior head, bordered anteriorly by a light brown band between eyes; a W-shaped marking on anterior dorsum; and a chevron-shaped marking on posterior dorsum. Shank and foot with one distinct dark crossband each, another dark crossband on anterior hand. Ventrally, the throat is dark brown and this dark colour fades at the level of the chest into a whitish colour on posterior belly. Limbs light with some dark brown pigment.

In life ( Fig. 1 ), two series of regularly arranged and light-coloured small tubercles recognizable on the dorsum, with five and three tubercles bordering the anterior edges of the W-shaped and chevron-shaped dark markings, respectively. In life ( Fig. 1A ), the colour was very similar to that in preservative but more contrasted. The interorbital band was posteriorly beige. The iris was uniformly bronze. Throat and chest were grayish. The yellow ventral colour extended onto the lateral part of the inguinal region. Also the finger and toe discs (especially of first finger) were yellowish.

Variation

The two ZSM paratypes are very similar in external morphology and colour pattern when compared to the holotype ( Table 1 ), but have a thin light middorsal line, and (in preservative) ventrally less dark pigment, especially in ZSM 351/2005 which is mostly light coloured ventrally. The UADBA paratypes were not available for detailed studies but were in general similar to the ZSM paratypes.

Natural History

Numerous specimens of the new species were heard in the evening in dense primary forest directly next to Camp Simpona campsite, calling from leaves in bushes and on trees at perch heights of 1-2 m above the ground.

Advertisement calls

Calls of the holotype (ZSM 349/2005) were recorded at Camp Simpona, Marojejy National Park, on 15 February 2005 (19:20 h) at 21.1°C air temperature. They have been published by Vences et al. (2006; CD3, Track 64). The call is a single melodious note that is repeated at regular intervals. Note duration ranges from 384-443 ms (418 ± 16; n = 11), duration of intervals between notes varies between 2504- 3200 ms (2797 ± 243; n = 10). Note repetition rate is approximately 18-19 notes/minute. The dominant frequency ranges between 3990-4028 Hz (4010 ± 13; n = 11).

Molecular differentiation

DNA sequences of various mitochondrial genes determined from the holotype of Platypelis ravus were included in a comprehensive molecular analysis of cophyline phylogeny, under the name Platypelis sp. 2 ( Wollenberg et al. 2008), and are deposited in GenBank under accession numbers EU341101 (12S and 16S genes) and EU341035 (cytochrome b gene). According to this study, the species is deeply genetically divergent from other Platypelis and was grouped by some analyses as sister species of Platypelis milloti . According to Vieites et al. (2009) the pairwise uncorrected sequence divergence (p-distance) in a fragment of the 16S rRNA gene of P. ravus (as P. sp. 4) to all other cophylines was above 6%.

Figures

Fig. 1. Platypelis ravus sp. nov. in life. A. Dorsolateral view of ♂ paratype (ZSM 350/2005) from Marojejy National Park. B. Ventral view of same specimen (ZSM 350/2005). C. Dorsolateral view of ♂ holotype (ZSM 349/2005).