Kenyaphrynoides vulcani, Liedtke & Malonza & Wasonga & Müller & Loader, 2024

Liedtke, H. Christoph, Malonza, Patrick K., Wasonga, Domnick V., Müller, Hendrik & Loader, Simon P., 2024, A new genus and species of toad from Mount Kenya illuminates East African montane biogeography, Zoological Journal of the Linnean Society 202 (1), pp. 1-12 : 5-9

Kenyaphrynoides vulcani sp.nov.

Holotype: NMK A6217 , male. Collected on 9 September 2015 in Mount Kenya Forest in Chogoria Forest Block , Tharaka-Nithi County (0°12 ʹ 25.4″S, 37°30 ʹ 02.4″E, elevation 2396 m; Fig. 1 ) by Domnick V. Wasonga and Joash Nyamache .

Description of holotype: For all measurements, see the Supporting Information (Table S1). Medium-sized male frog (45.2 mm SUL, 42.9 mm SVL), body elongate. Body width 15.0 mm, head width 15.7 mm. Arms and legs relatively long, gracile ( Figs 3 , 4 ). Outline of head in dorsal and ventral view oval, snout blunt. Eyes not visible in ventral view. Canthus rostralis flat, obliquely directed. In dorsal view, snout distinctly raised bulge, starting from anterior edge of the eye along to each nostril [canthus rostralis]. Lateral snout margins slightly expanded and curved at margin of canthus rostralis and midline of head, resembling upper parts of two parallel, sausage-shaped structures from eye to snout. Nostrils laterally directed, 3.5 mm apart, much nearer to apex of snout (one-quarter of total distance from snout tip to eye) than eye. Ventrally, chin region relatively smooth, with small glands present on jaw line. Tongue present, without any papillae. Choanae present on anterior part of roof of mouth. Eyes large (4.6 mm). No tympanum visible. Interorbital distance (5.4 mm) almost twice the internarial distance (3.5 mm).

Dorsal body surface with glandular masses symmetrically distributed along the midline. Dorsum glandular, particularly around the parotoid region anteriorly and laterally, glands not coalesced into recognizable parotoid gland. Glandular masses circular, ≤ 1.5 mm, shown as darker or lighter coloured areas on dorsum. Ventral skin granular. Vent relatively smooth, lacking ornamentation or spines, ventrally displaced, with overhanging dorsal skin flap. A lateral incision on the ventral side, and on ventral side of the right thigh, with ~ 15 mm × 3.5 mm strip of skin and musculature missing.

Arms moderate in size, with slightly thickened forearms, barred brown and cream. Fingers moderately long, lacking webbing, with expanded spatulate tips on fingers III – V. Finger II blunted and somewhat flattened, but tip not expanded. Palm with enlarged basal tubercle. Thin, elongated tubercle at base of thumb (finger II). Smaller tubercles present on each finger joint. Finger II shorter than III, IV, and V; III and V equal in length, finger IV longest (15.8 mm). Black spines resembling nuptial pads with papillary epidermal projections (see Luna et al. 2018) on dorsal surface of first joint on finger II, ~ 20 in total, grouped but not overlapping ( Fig. 3B ). A smaller number of spines coalescing at base of first finger tip. No spines on ventral surface.

Legs long, with tibiotarsal articulation reaching level of snout. With a larger, broadly oval inner tubercle at base of toe I and a smaller, more elongated outer tubercle at base of toe V. Inner tubercle about double the size of outer tubercle (see Fig. 4D ). Toes relatively long, thin, lacking webbing apart from a thin fringe at the base of each toe. Toe IV longest (23.7 mm), with III, V, II, and I in descending order of length. Tips of toes slightly swollen and expanded, spatulate in shape.

Specimen mottled brown and cream dorsally, with darker brown mottling anteriorly. Snout dark brown. Legs barred brown and cream. Ventral side cream.

Coloration of species in life: The dorsum dark brown, with light green patches. Light green coloration more dominant on lateral sides. The background colour of upper surfaces of arms and legs light green with three dark bands (two on femur and one on tibia, ~ 8 mm in thickness). Venter beige, with pinkish coloration on groin, chest, and neck. Throat whitish, especially margins of jaws. Prominent white-tipped glandular warts scattered across vent, fewer on limbs.

Skeletal morphology: Skull nearly as long as wide, with bluntly pointed snout formed by nasals and premaxillae ( Fig. 5A ). In lateral view, dorsal side of skull tapers slightly towards tip of snout, ending abruptly, with alary processes of premaxillae nearly vertical. Jaw articulation slightly below anterior end of otic capsule. Dorsally exposed part of nasal longer than wide, forming anterior-most border of orbit. Edges of the nasal, especially anteriorly and posteriorly, irregular. Sphenethmoid single, poorly ossified, almost completely exposed dorsally. Frontoparietal with somewhat irregular medial edge; both nasal and frontoparietal not in contact with their antimeres medially. Prootic poorly ossified. Ossified columella or operculum absent. Premaxilla toothless, alary process relatively broad and short (about half as wide as long), widely separated from nasal and about as long as pars dentalis. Palatine shelf of premaxilla with deep, V-shaped medial notch. Septomaxilla small, with median notch, slim, pointed dorsal process, and more broad, blunt posterior process. Maxilla toothless, terminating posteriorly somewhat before otic region. The quadratojugal relatively thin, with an expanded, knob-shaped posterior end, not in direct contact with maxilla. Pterygoid relatively broad and stout, with more slender posterior ramus extending ventrally towards jaw articulation to about level of end of squamosal; a slightly shorter, broader medial ramus extends towards, but terminates well before, the prootic. Palatine slender, slightly curved, isolated rod on right side of skull, slightly longer and contacting pterygoid on left side. Vomer relatively short, stout, with weakly developed, triangular lateral process. Cultriform process of parasphenoid broadest immediately anterior of prootic and gradually narrowing anteriorly, ending with irregularly shaped, broadly rounded tip that narrowly overlaps with posterior edge of sphenethmoid ventrally. Lateral processes of parasphenoid slightly more than twice as long as wide, angled backwards by ~10°. Squamosal triradiate: a long ventral ramus increases in width towards jaw articulation, ending there in a broadly rounded arch; an otic ramus slightly longer than half the ventral ramus, tapering to a point slightly above midline of otic fenestra; a short, broad zygomatic ramus about half the length of otic ramus.

Eight presacral vertebrae, with transverse processes on presacral vertebrae 2–8. These are directed anterolaterally on vertebra 2, slightly posterolaterally on vertebra 3, posterolaterally on vertebrae 4 and 5, and roughly laterally on vertebrae 6–8. Sacral diapophyses broadly triangular, about twice as wide laterally as medially, with the lateral width about double the width of centrum. Urostyle relatively straight and even, with slight, rounded dorsal keel on its anterior half.

Pectoral girdle comprises clavicle, coracoid, scapula, and suprascapula; ossified sternum and omosternum absent. Clavicle slender, gently curved, extending medially almost to midline of pectoral girdle, without contact with its antimer. Coracoid relatively broad, with enlarged lateral and medial ends, with medial end being ~2.5 times the width of narrowest part of coracoid. Scapula directed dorsolaterally and relatively stout, with greatest width being about two-thirds its length. Suprascapula rather robust, slightly longer than scapula, distinctly L-shaped. Slightly offset positions of coracoids in cross-section suggest an arciferal girdle, but exact anatomy is difficult to assess from uncontrasted computed tomography scan.

Pelvic girdle consists of ilium, ischium, and pubis, with pubis only weakly ossified. Ilium, ischium, and pubis not sutured or fused; acetabulum not completely ossified. Ilium and ischium seem well ossified; pubis smallest and seemingly less well ossified; no crest on shaft of ilium.

The humerus is subtly longer than radioulna, with low dorsal crest extending medially from its lateral end for about two-thirds its length; with broad flange-like crest anteromedially, extending for about one-quarter to one-third the length of humerus. Carpal elements only poorly ossified; phalangeal formula 2-2-3-3 on manus; terminal phalanges broadly expanded, T-shaped terminally on fingers III – V, less pronounced on finger II. T-shape with broad crossbar, giving it a more chisel-like appearance. Femur and tibiofibula near equal in length. A small and a tiny sesamoid are present at ankle joint. Tibiale and fibulare equal in length, tibiale subtly more slender in width. Phalangeal formula 2-2-3- 4-3 on pes, with distal tips of distal phalanges broadly expanded, but less extensively than in manus.

Habitat and natural history: The specimen was collected in September, during the dry season, and midday temperatures were relatively hot. It was collected in a pitfall trap in a moist indigenous montane forest with streams nearby (Supporting Information, Fig. S1 ). The habitat had a good amount of dry leaf litter, moss-covered tree trunks, and fallen logs. The nights and better parts of the morning had heavy mist cover, and the forest received some amount of rain in the afternoons within the week when the specimen was found.

The forest and moorlands of Mount Kenya have been sampled for amphibians in various locations (see Malonza 2015). In brief, surveys in 2008, 2009, 2015, 2017, and 2019 sampled forest blocks including Naro Moru, Chogoria, Irangi, Sirimon, and Kamweti between elevations of 1550 and 3392 m and yielded 84 anuran individuals in total ( Malonza 2015, Malonza and Bwong 2023). Kenyaphrynoides vulcani (one individual) was found within the Chogoria forest with five other species: Hyperolius cystocandicans Richards and Schiøtz, 1977 (seven), Amietia nuti (Boulenger, 1896) (two), Phrynobatrachus sp. (one) Hyperolius montanus (Angel, 1924) (five), and Amietia witei (Angel, 1924) (three). Surveys across all forest blocks gave cumulative numbers of specimens including: Amietia nuti (seven), Amietia witei (17), Cacosternum kinangopensis Channing and Schmitz, 2009 (12), Hyperolius cystocandicans (32), Hyperolius montanus (Angel, 1924) (15), Kenyaphrynoides vulcani (1), and Phrynobatrachus sp. (1). It is interesting to note the relative rarity of K. vulcani in comparison to most other species collected on Mount Kenya. Whether this reflects the difficulties in observations, or a small, potentially declining population is difficult to say but requires further research.

No observations of the breeding biology of K. vulcani were made other than the presence of nuptial spines on the single specimen that was collected.

Vocalizations: Not known.

Etymology: The name vulcani is in reference to the more recent, volcanic origins of Mount Kenya, the only locality from which this species is known. The species name is a noun in the genitive form (‘of the volcano’).

Common name: Kenyan Volcano toad.

Figures

Figure 1. Map of Eastern Africa showing the distribution of Kenyaphrynoides vulcani and related bufonid genera (red polygons). Spatial data were obtained from the IUCN Red List (2022). Also shown are the approximate traces of the Western and Eastern branches of the East African Rift system (translucent white polygons).

Figure 3. Artistic rendition of Kenyaphrynoides vulcani (A). Drawing of a dorsal view of the left hand of the holotype (B), and dorsal (C) and ventral (D) photographs of the holotype prior to preservation.

Figure 4. Lateral (A), dorsal (B), and ventral (C) views, and ventral aspect of right foot (D) and left hand (E) of the holotype of Kenyaphrynoides vulcani.

Figure 5. Dorsal (A), lateral (B), and ventral (C) view of the skull, and dorsal (D) and ventral (E) view of the whole skeleton of the holotype of Kenyaphrynoides vulcani. Features indicated are the cleithrum (cl), coracoid (co), premaxilla (pmx), prootic (pro), sphenethmoid (sph), squamosal (sq), and suprascapula (ssc).