Phrynobatrachus ambanguluensis, Greenwood & Loader & Lawson & Greenbaum & Zimkus, 2020

Greenwood, Laura, Loader, Simon P., Lawson, Lucinda, Greenbaum, Eli & Zimkus, Breda M., 2020, A new species of Phrynobatrachus (Amphibia: Anura: Phrynobatrachidae) from the Northern Mountains of Tanzania, Journal of Natural History 54 (1 - 4), pp. 63-85 : 78-81

Phrynobatrachus ambanguluensis sp. nov.

Holotype. MCZ: Herp:A-138315, adult male collected by Lucinda Lawson and D. Luke Mahler on 15 March 2007 in the Ambangulu Tea Estate in the West Usambara Mountains (−5.070933, 38.420217, 1183 m). See Figure 9 .

Paratypes. West Usambara Mountains : MCZ: Herp:A-12776, 12778-779, 12785, 138296, 138299-301, 138305-306, 138312-313, BMNH 1974.64 - 79 , 1974.81 - 95 , 1982.545 - 550 , 1986.484 , 2005.1370 – 1372 . Please refer to Appendix 2 for further details.

Referred material. BMNH 2005.952 – 953 Kindoroko Forest Reserve, North Pare Mountains, Tanzania. Please refer to Appendix 2 for further details.

Diagnosis

The species is assigned to Phrynobatrachus based on the following characteristics: lack of webbing between fingers, presence of mid-tarsal tubercle, elongated inner and small round outer metatarsal tubercles, unpaired subgular vocal sac in males, and tympanum present.

The large size of P. ambanguluensis (maximum SVL of males 45 mm, of females 40 mm) distinguishes this puddle frog from most of the species of the genus, only matched by P. acutirostris , P. dendrobates , P. irangi , P. krefftii , and P. sulfureogularis in East Africa. The presence of a bright yellow throat colouration in breeding males distinguishes the species from all other species from East and Central Africa except P. minutus , P. sulfureogularis , P. uzungwensis , P. dendrobates , and P. krefftii . Other characteristics that distinguish P. ambanguluensis from the eastern species within Phrynobatrachus include: absence of a spiny tubercle on the eyelid (present in P. breviceps and P. rungwensis ); tympanum present and smaller than eye (not visible in P. keniensis , P. mababiensis , P. parvulus , P. rungwensis , P. scheffleri , P. stewartae , P. ukingensis , and P. uzungwensis ); throat of males being smooth (asperities present in males of P. acridoides , P. bullans , P. natalensis , P. rungwensis , P. kinangopensis sometimes present in P. perpalmatus , P. ukingensis , P. mababiensis , P. parvulus ); males lacking femoral glands (present in P. scheffleri , P. ukingensis , P. stewartae , P. parvulus ); finger and toe tips with swollen discs (not present in P. irangi , P. rungwensis , P. keniensis , P. auritus , P. bullans , P. perpalmatus , P. stewartae , P, parvulus ); fingers without webbing; back smooth with limited number of tubercles (unlike P. scheffleri , P. uzungwensis , P. rungwensis , P. natalensis , P. mababiensis , P. stewartae ); toes of males without spinelike plantar tubercles (only commonly seen in P. irangi , P. versicolor ); upper jaw extending beyond lower jaw (whereas upper snout slightly overhanging lower jaw in P. krefftii ); cartilage cushion darker brown colouration than tympanic membrane (lighter than the tympanum in P. krefftii ).

Morphometric comparison of large-bodied, yellow-throated Phrynobatrachus from the Usambara Mountains cannot be definitively separated. The new species can be distinguished from P. krefftii by a number of characteristics. Most notably is the shape of the snout, with the upper and lower jaw in P. krefftii roughly extending to the same point in lateral view, whereas the new species has a snout that notably extends beyond the lower jaw in both ventral and lateral view. The snout is rounded in dorsal view in P. krefftii , with the new species having a more pointed, arrow-like shape. The colour in specimens of the new species is much darker, contrasting with P. krefftii , which is typically lighter with more distinct patterning. The colour of the tympanum differs between the two populations as well; in P. krefftii , the cartilage cushion is lighter brown than the tympanic membrane, but in the new species, the opposite is true and the cartilage cushion is darker than the tympanic membrane.

Description of holotype

Relatively large male specimen (38 mm) with smooth skin; see Table 3 for measurements. Head shape pointed with a tapered snout. Canthus rostralis is obliquely directed and flat. Snout distinctly overhanging the lower jaw. Nostrils at the end of the blunt snout near the edge of the canthus rostralis positioned closer to the apex of the snout (1/3 of the total distance of the eye to the snout end) than the eye. Tongue present with medial conical papilla. Choanae present on anterior part of the roof of the mouth. Eyes are large, about 1.5x the size of the tympanum. Tympanum present and distinct, circular in shape. Interorbital distance is twice as large as the upper-eyelid distance. Vocal sacs are positioned as unpaired in subgular region, but not easy to decipher in the specimen. No glandular mass under the armpits. Fingers moderately long, lacking any webbing with distal-expanded toe tips – though only slightly. Thick nuptial pads present on the thumb. First finger shorter than second and third, with second finger longer than the third. Palm with a long, thin inner metatarsal tubercle, directed along the inner edge of the nuptial pad. An outer metatarsal tubercle is present, rounded and relatively large. Tibio-tarsal articulation reaches the snout with the knee joint adjacent to the anterior margin of the tympanum.

Legs are long with muscular thighs. Tarsal tubercle present. Toes are relatively long and thin, with extensive webbing (1e(0), 2i(1), 2e(0), 3i(0.5), 3e(0), 4i(1.5), 4e(0), 5i(0)). Tips of toes slightly swollen and expanded. Tubercle present on the inner toe, long and thin, directed along the inner edge of the first toe, a small-rounded tubercle present on the outer/mid-portion of the anterior margin of the foot. Small white spines found regularly distributed along with all toes between tubercles.

The specimen has brown mottling dorsally, with a darker thin brown interorbital band that is light brown edged on the anterior side at the mid-line of the eyes. Snout is light brown. The legs are brown with slightly darker brown banding along the legs. Ventrally, the lower jaw is edged with brown overlaying a cream-yellow colouration. The gular flap is lighter brown coloured, with a darker cream/brown ventral region, mottled with light brown along edges of the legs.

Variation

Mature males with bright yellow throat with unpaired subgular vocal sac; females with brown and slightly speckled throat lacking vocal sacs. SVL up to a maximum of 45 mm in males, female SVL up to 40 mm ( Tables 1 and 2); these lengths show compared to krefftii. Smallest specimen recorded was 12.1 mm juvenile, and the sex was indeterminate (BM 1974.91). Furthermore, some white spines on lower foot in concentrations typical of P. krefftii , but this is a highly variable trait.

The North Pare specimen has not been sampled genetically but qualitative characteristics (pointed snout with the upper jaw extending beyond lower jaw) place it more closely with P. ambanguluensis . Morphometric analyses are uncertain with both a male and female specimen placed outside the 95% confidence intervals of either P. krefftii or P. ambanguluensis . Genetic data and more specimens are required before this population can be accurately assessed taxonomically but in the meantime the population can be referred to as P. cf. ambanguluensis .

Colouration of holotype in life

In life, dark brown above; a blackish cross-bar between the eyes, light-edged in front; limbs slightly lighter than torso with indistinct darker brown cross-bands; ventral surface cream with diffuse brown mottling; a prominent brown band across the throat is present; lower jaw edge defined with dark brown against a distinct yellow throat sac. See Figure 10 .

Colouration of holotype in preservative

In preservation, colouration is similar to that in life, with fading of the yellow underside to a yellow-beige. Yellow of the throat in male specimens is faded, but still distinctly yellow. See Figure 9 .

Habitat and natural history

The species is diurnal, found in submontane and montane forest and streams in the West Usambara Mountains (1450 – 1850 m) and North Pare Mountains (unknown altitudinal range). Phrynobatrachus ambanguluensis has not been observed in deforested habitats, but it has been found in modified stream habitats inside forests, such as dams and artificial waterbodies. Breeding takes place in damp and moist areas alongside streams, and egg masses are attached to rocks or vegetation above the water. Similar to P. krefftii , adults have been observed in close proximity to egg masses. Limited observations have been made regarding male territoriality, and it is yet undetermined if there is visual signalling behaviour similar to that observed in P. krefftii (e.g. Hirschmann and Hödl (2006)).

Figures

Figure 9. Male holotype (MCZ:Herp:A-138315) of Phrynobatrachus ambanguluensis sp. nov. Left: ventral view of left hand (top); ventral view of left foot (bottom). Right: dorsal view of body (top); ventral view of the body (middle); lateral view of the body (bottom). Scale bar is 1 mm.

Figure 10. Phrynobatrachus ambanguluensis sp. nov. in life from West Usambaras, a) adult male MCZ: Herp: A-138296, b) adult female MCZ:Herp: A-138301, c) juvenile MCZ:Herp: A-138307, and, d) stream habitat of Phrynobatrachus ambanguluensis (Mazumbai Forest Reserve).