Astylosternus laticephalus, Rödel, Mark-Oliver, Barej, Michael F., Hillers, Annika, Leaché, Adam D., Kouamé, N’Goran G, Ofori-Boateng, Caleb, Assemian, Emmanuel, Tohé, Blayda, Penner, Johannes, Hirschfeld, Mareike, Doumbia, Joseph, Gonwouo, Legrand Nono, Nopper, Joachim, Brede, Christian, Diaz, Raul, Fujita, Matthew K., Gil, Marlon & H, Gabriel, 2012

Rödel, Mark-Oliver, Barej, Michael F., Hillers, Annika, Leaché, Adam D., Kouamé, N’Goran G, Ofori-Boateng, Caleb, Assemian, Emmanuel, Tohé, Blayda, Penner, Johannes, Hirschfeld, Mareike, Doumbia, Joseph, Gonwouo, Legrand Nono, Nopper, Joachim, Brede, Christian, Diaz, Raul, Fujita, Matthew K., Gil, Marlon & H, Gabriel, 2012, The genus Astylosternus in the Upper Guinea rainforests, West Africa, with the description of a new species (Amphibia: Anura: Arthroleptidae), Zootaxa 3245, pp. 1-29 : 16-22

Astylosternus laticephalus sp. nov. Rödel, Hillers, Leaché, Kouamé, Ofori-Boateng, Diaz & Sandberger

Figs. 9–12

Holotype. ZMB 75449 (field and tissue #: ATE10, female, 58.6 mm), Ghana, Atewa Forest Reserve, 6.23375 / - 0.56557, 14 April 2007, forest around stream next to road, coll. C. Ofori-Boateng, A. Hillers & G. Segniagbeto.

Paratypes. Ivory Coast: MTD 48026 (field and tissue #: Ba04.24, female, 62.2 mm), ZMB 75454-75458 (Ba04.26, subadult, 45.5 mm; Ba04.25, female, 62.5 mm; Ba04.21, female, 64.4 mm; Ba04.22, subadult, 43.3 mm; Ba04.23, female, 58.4 mm;), Banco National Park, 5.41667/ -4.10500, rainy season 2004, swampy forest, coll. N.E. Assemian, B. Tohé & G. Kouamé; MNHN 1993.6073 (male, 53.8 mm), 1999.7333 (female, 54.8 mm), 1999.7334 (male, 48.7 mm), 1999.7335 (female, 59.8 mm), 1999.7736 (female, 52.6 mm), 1999.7337 (female, 51.8 mm), Banco National Park, Abidjan; Ghana: ZMB 75459 (AF4, juvenile, 25.6 mm), ZMB 75459-75460 (AF 3 juvenile; 26.7 mm; AF2, tadpole), Afao Hills Forest Reserve, 6.25461 / -2.29492, riparian forest around small stream in valley, coll. C. Ofori-Boateng & A. Hillers; ZMB 75450-75453 (COB90, juvenile, 34.7 mm; COB318, subadult, 40.8 mm; COB119, juvenile, 38.6 mm; COB123, juvenile, 31.7 mm), Western Province, Ankasa Conservation Area, pristine forest along streams in dry season, coll. C. Ofori-Boateng; MVZ 244910 (female, 67 mm), Ankasa Conservation Area, 5.28173 / -2.64022, 26 June 2004, wet evergreen forest area, trail adjacent to the bamboo cathedral, coll. A.D. Leaché & R. Diaz; MVZ 244909 (juvenile, 35 mm), 28 June 2004, approximately 1 km farther from the bamboo cathedral, other data as MVZ 244909.

Additional material. ZMB 77461 (field# AF 03), tadpole, Ghana, Afao Hills Forest Reserve, 6.25461 / - 2.29492, riparian forest around small stream in valley, coll. C. Ofori-Boateng & A. Hillers; ATE7 (tissue only), juvenile, 25.8 mm; ATE8 (tissue only), juvenile, 28.6 mm; ATE27 (tissue only), male, 45.6 mm, Ghana, Atewa Forest Reserve, 6.23375 / -0.56557, 15 April 2007, swampy area next to small stream, in valley in forest, coll. C. Ofori-Boateng, A. Hillers & G. Segniagbeto; COB2202 (collection Ofori-Boateng, Kumasi, Ghana), Ghana, Atewa Forest Reserve, coll. C. Ofori-Boateng; three adult specimens without number (amphibian reference collection at University Abobo-Adjamé, Ivory Coast), male (51.0 mm), females (60.0, 67.0 mm), Ivory Coast, Banco National Park, 5.41667/ -4.10500, 5 May 2004, forest close to Banco River, coll. N.E. Assemian, N.G. Kouamé & B. Tohé.

Diagnosis. Astylosternus laticephalus sp. nov. has the typical body shape of frogs of the genus Astylosternus , however, with exceptionally broad heads, i.e. broader than in A. occidentalis ; males of the new species without spines on throat and belly (always present in A. occidentalis males); males without nuptial black skin layer in pectoral region (present in male A. occidentalis from western Guinea); back brownish to brownish red, always with distinct red dots (red dots only rarely present in A. occidentalis ); bicoloured iris, grey with a reddish upper third ( A. occidentalis always with uniform grey iris). A. laticephalus sp. nov. differs from A. occidentalis by a mean of 3.2% (range 2.9-3.7%) in the investigated part of the 16S rRNA gene. Genetic divergence to the morphologically most similar Central African species, A. diadematus , was 11.9%.

Description of the holotype [measures in mm]. The holotype is an adult female with a snout-vent length of 58.6; head width 22.7; head as long as broad; interorbital distance narrower than length of upper eyelid; snout rounded in dorsal view, obtuse in lateral view, longer than eye diameter; eyes large (7.9) and protuberant directed anterolaterally; interorbital distance 7.2; pupil vertically elliptical; eye diameter larger than tympanum diameter, 5.3; tympanum vertically elliptical; supratympanal fold from posterior vertical midpoint of orbit to meet with dorsal border of tympanic annulus, where descent is sharp and terminates at half the vertical diameter of the tympanic annulus dorsally to the axilla; nares closer to snout-tip (2.7) than to eye (5.5), nostrils oriented posterolaterally; internarial distance 4.4; canthus rostralis rounded and straight; loreal region slightly concave and gradually sloping laterally; single, small, tooth-like process at lower jaw symphysis, with corresponding socket in between premaxillae; upper premaxillae and maxillae with numerous teeth; vomerine teeth in form of two hemispherical odontophores, perpendicular to body axis, almost being in contact to each other medially, each with row of teeth like tips (5 left, 6 right); distance from odontophores to elliptical choanae slightly larger than maximum length of odontophores; choanae almost equal in size to odontophores; tongue broadly heart shaped, deeply notched anteriorly, densely beset with small papillae, extends over entire length of lower jaw; posterior 2/3 of tongue free.

Forelimbs robust, fingers slender and long; prepollex absent; first finger 10.3, almost double the length of second finger (5.1); relative finger lengths I>III>II>IV; finger tips broadened without forming discs; subarticular tubercles large, subconical, protruding distally; thenar and palmar tubercles large and elliptical; supernumerary tubercles absent; number of subarticular tubercles on digits I-IV: 1, 1, 2, 2; no digital webbing; hind limbs short and robust; femur length 28.3, almost equal to tibia 28.4; tibia-fibula with longest toe 38.4; relative toe lengths IV>III>V>II>I; shortest toe (4.2) almost double the length of inner metatarsal tubercle (2.3); inner metatarsal tubercle large, elliptical; toe tips broadened without forming discs; number of subconical subarticular tubercles on toes I-V: 1, 1, 2, 3, 2; supernumerary tubercles absent; traces of webbing between toe bases; no skin fringes along toes. Tip of toe IV on left foot missing.

Skin on head, back, belly and throat predominantly smooth; small whitish spines scattered on back, dorsal parts of extremities and eyelids; white warts posterior to angle of mouth, ventral from tympanum; posterior region of thighs areolate; irregularly spread narrow low tubercles along flanks; no tubercles or warts on forearms or interocular region; head with white scratches (scars).

Base colour of dorsum in preservation is a light brown to reddish brown; back with irregularly arranged and shaped light beige spots; upper eyelids greyish; head laterally with two darker bars, the posterior one below eye; upper and lower lips white; supratympanic fold anteriorly rimmed thin black; warts on flanks beige; forelimbs dorsally light brown, slightly mottled beige, first two fingers almost uniform white; hind limb colour as forelimbs, dark bordered cross bars indicated in thighs (4) and lower legs (5-6); throat, belly, ventral parts of fore- and hind limbs uniform white or creamish; only ventral part of feet reddish brown, metatarsal tubercle and subarticular tubercles creamish white.

Variation. Females seem to be larger (up to 67.0 mm; MVZ 244910) than males (53.8 mm), although the small sample size of the latter (N = 2) does not allow for generalization. The tympanum shape varies between vertically elliptical (most vouchers) to round; the supratympanic fold is sometimes thin to absent; sometimes tympanic membrane prominent within faint tympanic annulus. Other measures and indices identical between the two sexes; values are summarized in Tabs. 1 and 2.

Dorsal and lateral skin texture can consist of many irregularly spaced small roundish warts, not arranged in rows, sometimes fused to small ridge like structures ( Fig. 11 ). Males have paired subgular vocal sacs, visible in preserved frogs as slightly loose, granular black skin near the angles of the mouth; males with large brown nuptial pads on the external side of the thumb. Canthus rostralis in males more prominent bulging and rounded; males with more massive forearms than females. In contrast to other western West African Astylosternus , A. laticephalus sp. nov. males in breeding condition, lack spines on throat and belly.

The dorsal base colouration in life consists of a light grey, brown, reddish brown or almost black; all specimens exhibit a more or less dense pattern of smaller to larger, irregularly shaped red spots on back; smaller black or brown spots may be present, in particular in juveniles; iris greyish, upper third reddish to orange; the anterior part of the eyelids bright yellow to red blotches, connected by a very conspicuous interorbital stripe of the same colour; snout tip and area posterior to interorbital stripe, including posterior part of eyelid, darker than rest of back, this pattern sometimes consisting of a symmetrical pair of triangular shaped black spots ( Fig. 11 ); frenal area dark as snout tip; loreal area distinctly lighter coloured than snout tip; light infraorbital batch; supratympanal ridge usually bordered by thin black line; fore and hind limbs with or without distinct black cross bars; lateral colour gradually fainting from back colour to whitish venter, with irregularly scattered black points; ventral coloration (throat and abdomen) creamish-white; ventral surface of thighs and arms creamish-yellow with reddish brown mottling around lateral margins of limbs.

In preservative all patterns and coloration almost as in life, but faded; the red dorsal spots remain as light beige spots.

Tadpole [measures in mm; description based on ZMB 75460]. Exotrophic, lentic tadpole; Gosner stage 39; total length 62.1; body broad almost as long as wide, slightly elliptical in dorsal, slightly depressed in lateral view (possibly a preservation artefact); body length 23.8; body width 24.2; sides of body slightly concave, snout in dorsal view broadly rounded, a bit more pointed in lateral view; large lateral sacs originating posterior to eyes run along flanks; small eyes, positioned dorsolaterally, pupil round; nares small, positioned dorsolaterally, closer to snout trip than to eyes; oral apparatus in anteroventral position; dorsal lip wide and smooth, with large anterior gap between marginal papillae; lateral papillae ventral lip with large, uni- or biserial marginal papillae; upper jaw sheath massif, broad U-shaped, strongly serrated margin, most central “tooth” most prominent; lower jaw sheath massif, V-shaped, margin strongly serrated; labial tooth-row formula 1:1+1/3; all keratodont rows on skin sheaths; labial keratodonts unidenticulate, connected by a hyaline skin; vent tube dextral; spiracle sinistral (almost invisible); very long tail axis (> 2.5 times body length); tail axis height largely exceeding height of dorsal and ventral fin, both fins very narrow; dorsal fin originates slightly posterior to tail body junction; dorsal fin almost parallel to tail axis up to rounded tip; no pores (neuromast canals) visible (possibly due to poor preservation or advanced developmental stage); body more or less beige, mottled with dark brown, tail fin brown to almost black in last third of tail. Newly metamorphosed froglets measured 25.6–28.7 mm (N = 2).

Natural history. Not much is known about the biology of the new species. Astylosternus laticephalus sp. nov. lives in lowland rainforest habitats ( Fig. 13 ), mostly close to small or mid sized streams ( Rödel et al. 2005; Assemian et al. 2006). In Banco National Park, Ivory Coast we recorded the new species in the leaf litter of swampy areas in closed canopy forest, open forest and in natural forest gaps, both in close vicinity to the River Banco and in larger distance (about 1 km) from the river ( Assemian et al. 2006). A total of 12 specimens were only observed during the rainy season, 11 of them during the night. In the Ankasa Conservation Area we found the new species in wet evergreen forest on a trail adjacent to the Bamboo Cathedral ( Fig. 13 b).

Distribution. So far A. laticephalus sp. nov. is known from one forest in eastern Ivory Coast, the Banco National Park ( Assemian et al. 2006), and various sites in Ghana: Afao Hills Forest Reserve, Draw River Forest Reserve and Ankasa Conservation Area in south-western Ghana ( Rödel et al. 2005; this paper), and Atewa Range in southern-central Ghana ( Fig. 8 ). The latter site was chosen as type locality of the new taxon to underline the outstanding importance of this mountainous region for the Ghanaian biodiversity.

Conservation status. The distribution of the species from eastern Ivory Coast to southern-central Ghana, including various protected areas (i.e. Banco National Park, Afao Hills Forest Reserve, Ankasa Conservation Area), seems to imply a IUCN RedList classification of “Least Concern”. However, rainforests in south-eastern Ivory Coast are under intense logging pressure and highly fragmented. Forests in south-western Ghana are better protected but likewise fragmented and the Atewa Range is currently under threat because of small scale mining activities and further plans to mine for gold, diamonds and bauxite on an industrial scale. We thus suggest classifying the new species as “Near Threatened”.

Etymology. The name derives from the Latin words latus for wide and the Greek Kεφάλɩ for head, referring to the conspicuous wide head of the new species.

Figures

FIGURE 8. Known records of West African Astylosternus taxa; circles: Astylosternus occidentalis, black circle: “ type locality ” (compare text); triangles: A. laticephalus sp. nov., black triangle: type locality; black square: Mont Péko, locality of A. sp. (for exact localities see Appendix 1); country boundaries, topography and three major rivers (Sassandra, Bandama, Volta) are indicated; map based on the ASTER Global Digital Elevation Model: www. ersdac. or. jp.

FIGURE 9. Astylosternus laticephalus sp. nov. female (holotype, ZMB 75449, 58.6 mm) from Atewa Forest Reserve, Ghana; dorsal (a) and ventral (b) view, portrait (c); ventral views of right hand (d) and right foot (e).

FIGURE 10. Left thumb in dorsal view with nuptial pad (a), left hand in ventral view (b) and throat (c) of adult male Astylosternus laticephalus sp. nov. (paratype, MNHN 1999.7334, 48.7 mm) from Banco National Park, Ivory Coast.

FIGURE 11. Life colouration of female and juvenile (c) Astylosternus laticephalus sp. nov. from Ghana, Ankasa Conservation Area (a, b, d, e, f, g) and Afao Hills Forest Reserve (c); b, d, f: MVZ 244910; c: ZMB 75459.

FIGURE 12. Mouth part of a Astylosternus laticephalus sp. nov. tadpole from Afao Hills, Ghana (ZMB 75460; Gosner stage 39; SVL: 23.8 mm).

FIGURE 13. Rainforest habitats of Astylosternus laticephalus sp. nov.; streams in Ankasa Conservation Area (a, b), and forest in Atewa Forest Reserve (c) and Ankasa Conservation Area (d), Ghana.