Tomopterna adiastola, Channing & Du Preez, 2020

Tomopterna adiastola sp. nov.

(fig. 5, 7, Appendices 2–3)

LSID urn:lsid:zoobank.org:act:

Specimens allocated to new species

Holotype

A male, SAIAB 105333 , collected in Cleveland Nature Reserve , Phalaborwa, Limpopo Province, South Africa ( 23.9824°S, 31.1885°E) by L. R. Minter on 20 January 2012.

GoogleMaps

Paratypes

A male, SAIAB 105334 with the same details as the holotype, GoogleMaps and two males, SAIAB 106225 & 106226) from Goo-Moremi Gorge , near Palapye, Botswana ( 22.5619°S, 27.4336°E) collected by LdP on 5 January 2015, GoogleMaps and a male SMR 10756 from Khorab in Namibia ( 19.6631°S, 17.3283°E). Other material examined is listed in Appendix 2. GoogleMaps

Diagnosis

The new species has been confused with Tomopterna cryptotis , and is similar to all other species of sand frogs in morphology and burrowing behaviour. It has an advertisement call of a rapidly-repeated series of high-pitched notes, the most common type of call in sand frogs. We assign it to the genus Tomopterna based on the presence of teeth on the maxilla, the inner metatarsal tubercle strongly flanged, the outer metatarsals bound into the sole, and the presence of vomerine teeth, all characters that distinguish the genus Tomopterna ( Poynton 1964) .

The following comparisons follow Wilson & Channing (2019). The new species has single subarticular tubercles, distinguishing it from those with divided tubercles: T. gallmanni , T. krugerensis and T. wambensis . It has more than three phalanges of the fourth toe free of web, distinguishing it from those with more webbing: T. elegans , T. gallmanni , T. luganga , T, marmorata , T. tandyi and T. wambensis .

Outer metatarsal tubercle absent, which distinguishes it from the species with prominent outer metatarsal tubercles: T. cryptotis , T. delalandii , T. elegans , T. kachowskii and T. tandyi . It has no tarsal tubercle near the tibio-tarsal articulation, which distinguishes it from T. cryptotis . A transverse dark interocular bar is present, which distinguishes it from the species without this pattern element: T. ahli , T. luganga and T. natalensis . This bar is variable in T. elegans , T. kachowskii , and T. tandyi . The back is smooth or has small warts, distinguishing it from T. gallmanni and T. tuberculosa , which have prominent dorsal tubercles.

The advertisement call consists of a rapidly-repeated series of high-pitched notes, distinguishing it from the knocking calls of T. krugerensis and T. gallmanni . The first two harmonics are emphasised (1536–1859 Hz; 3074–3718 Hz), although the first harmonic is sometimes weak or absent. Tomopterna natalensis also has two emphasised harmonics, but at lower frequencies (1272–1488 Hz; 2544–2976 Hz). It is further distinguished from the species with only a single harmonic emphasised, at a higher frequency ( T. wambensis , T. tandyi , T. ahli and T. sp. [from Beira]), and T. luganga , T. marmorata , T. delalandii and T. cryptotis with a single emphasised harmonic at a lower frequency. The call of T. elegans is unknown.

Tomopterna adiastola occurs sympatrically with T. cryptotis and T. tandyi . It can be distinguished from T. cryptotis which has a prominent tarsal tubercle near the tibio-tarsal articulation, a distinct outer metatarsal tubercle (weak or absent in T. adiastola ) and an advertisement call with the second harmonic emphasised. It differs from T. tandyi which has a weak outer metatarsal tubercle, and an advertisement call with a single harmonic emphasised at 2.5 kHz.

The uncorrected p -distances (as percentages) of T. adiastola compared to all other species of sand frogs based on 16S rRNA vary from 1.2 to 7.3 %. The uncorrected p- distances between T. adiastola and T. cryptotis are 6.3–7.3 % for 16S (Table 1) and 1.7 % for tyrosinase exon 1.

Colour patterns vary, with brown and grey predominating, and pale blotches and spots of red, orange and white present. A pale vertebral stripe and lateral stripes are sometimes present.

Description of holotype

A male (fig. 5, 7), SVL 38.7; body robust; head short (HL/SVL 0.31, HW/SVL 0.37), not wider than trunk, not longer than wide (HL/HW 0.85); snout short (SL/HL 0.46), rounded in dorsal view, truncated in profile, slightly projecting beyond lower jaw, narrow (SL/IND 1.40); canthus rostralis rounded; loreal region slightly concave; nostrils situated on slight projections, closer to the eye than to snout tip (ENL/SNL 0.75); eyes directed anterolaterally, slightly protruding, relatively small (ED/HL 0.36); eye diameter less than snout length (ED/SL 0.77); interorbital distance less than upper eyelid (IOS/ELD 0.48) and nearly equal to internarial distance (IOS/INS 0.93); internarial distance just less than eye diameter (IOS/ED 0.93); vomerine teeth small; tympanum visible, about half eye diameter (TD/ED 0.53); a continuous prominent glandular ridge below tympanum; upper jaw without dentition; choanae small, round, vomerine teeth absent; tongue notched posteriorly, 6.0 at widest part; median lingual processes present; vocal sac single, darkly pigmented anteriorly; dorsal surfaces of head, trunk and limbs generally smooth; ventral surface of limbs, gular and abdomen smooth. Arms slender; hand moderate (HND/SVL 0.22); tips of fingers not enlarged into discs; relative length of fingers: IV <II <I <III; subarticular tubercles single and distinct, with one on fingers I, II and IV, and two on finger III; fingers without webbing; thenar tubercle distinct; metacarpals without supernumerary tubercles; pale brown nuptial pads present on upper surface of fingers I and II.

Hind limbs stout, tarsal tubercle absent, tibia short (TL/SVL 0.40); heels not reaching each other when knees are flexed and thighs are held at right angle to body; tissue sample taken from right thigh; foot shorter than tibia (TL/FOT 0.91); relative length of toes: I <II <V <III <IV; toes without expanded discs; subarticular tubercles: one on toe I and II, two on toe III, three on toe IV and two on toe V; pedal webbing formula I 1 – 2 II 1 – 3 III 1 – 3.5 IV 3.5 – 2 V; thin margin of webbing extending to tips; inner metatarsal tubercle prominent and shovel-shaped, continuing as a tarsal ridge, smaller than eye diameter (IMT/ED 0.88); outer metatarsal tubercle absent. Measurements of the holotype and paratypes are presented in Table 2 View Table 2 .

Colour in life

The dorsal pattern of the holotype consists of dark brown patches with black and orange warts on a pale beige background (fig. 5). No pale vertebral or lateral lines are present. The transverse bar between the eyes is dark brown with orange flecks. The iris is pale golden-silver with dark veins. The glandular ridge below the tympanum is pale, tinged with orange. Small rounded tubercles are scattered over the back and sides. The flanks have irregular grey and white marbling. The upper surfaces of the limbs are brown, with darker brown large blotches. The venter is white with a black throat. In preservative, the pattern is clearly visible (fig. 7) as a darker brown on a paler brown background.

Paratype variation

The male from Cleveland Nature Reserve SAIAB 105334 (SVL 39.9) and the males from Goo-Moremi Gorge SAIAB 106225 & 106226 (SVL 36.3 and 37.4) have a morphology similar to that of the holotype, practically identical body proportions and colour patterns. The male from Khorab SMR 10756 (SVL 38.8) is brown with darker patches, a thin pale vertebral stripe, and pale lateral stripes. The glandular ridge below the tympanum is pale, tinged with orange.

Advertisement call

Calls were recorded at Bloemfontein, South Africa, and Bagani and Popa Falls in Namibia. The call consists of a number of rapidly repeated notes, which have the first two harmonics emphasised at 1536–1859 Hz and 3074–3718 Hz, although the first harmonic is sometimes weak or absent. The note repetition rate is temperature dependent, described by the equation: Note rate/second = (temperature × 0.75) – 7.67. In contrast, the call of T. cryptotis from Shamvura, Bagani and Popa Falls in northern Namibia has two frequencies emphasised, the first and second harmonics (fig. 2‒3).

Sequences

Sequences derived from the holotype and additional material are deposited in GenBank under accession numbers (16S): AF215506 View Materials , AY255090 View Materials , AY255099 View Materials , MK335431 View Materials , MN057690 View Materials and MN057692 View Materials ; and tyr: MN062050 View Materials , MN062057 View Materials and MN062060 View Materials .

Ploidy

Tomopterna adiastola has 2 n = 26, according to a study by Channing & Bogart (1996) on material from Bloemfontein in South Africa and Grootfontein in Namibia.

Tadpoles

The tadpole was described as Tomopterna cryptotis ( Channing et al. 2012) from specimens from the farm Orumbo-nord 199, in pools in the bed of the Okahua River, Namibia, collected by H. Berger-Dell’mour.

Distribution

This species is presently only known from northern Namibia, Botswana, Zimbabwe, Mozambique and South Africa ( Fig. 6 View Figure 6 ). Further studies are required to determine its range.

Habitat

This is a widespread species, common in pools in seasonal rivers and farm dams in grassland and savanna.

Etymology

The specific epithet is derived from the Greek ἀδιάςτολος, [ adiastolos], meaning ‘not distinguished, confusion’.