Hyperolius laticeps Ahl, 1931

Segniagbeto, Gabriel Hoinsoudé, Ohler, Annemarie, Rödel, Mark-Oliver, Luiselli, Luca & Dubois, Alain, 2024, Amphibians of Togo: taxonomy, distribution and conservation status, Zoosystema 46 (25), pp. 631-670 : 646-648

Hyperolius laticeps Ahl, 1931

REMARK

Onomatophore: holophoront (holotype) by monophory, ZMB 46529, juvenile frog ( Fig. 7 ). Onymotope (type locality): Togo; the ergonymotope ( Frétey et al. 2018) might be the vicinity of Bismarckburg (Sotouboua Prefecture, Centrale Region), the place where the collector, Leopold Fritz Wilhelm Edmund Conradt, was stationed from July 1892 to December 1893 ( Tillack et al. 2021), thus on the date of collection, the 17 December 1892.

COMMENTS ON THE IDENTITY OF THE HOLOPHORONT OF HYPEROLIUS LATICEPS

Ahl (1931) described a species from Togo on a single specimen with a colour pattern which is present in the species of the Hyperolius picturatus complex ( Kanga et al. 2021). This species was mentioned by Laurent (1958), SchiØtz (1967) and Frost (1985). Recent authors considered its taxonomic identity not resolvable. Laurent (1958) regarded its morphological characters more similar to Leptopelis without giving precise character states, but in Frost (1985) it was listed as a valid Hyperolius species. According to Tillack et al. (2021), the holophoront cannot be assigned to any species from West Africa. Consulted on 18 June 2023, the website Amphibian Species of the World lists the name among the “Nomina inquirenda”, unassigned to a living population. We mention this name, although it is not assigned to a taxon, as, applying the Principle of priority of the International Code of Zoological Nomenclature, after further studies, namely sequencing of the DNA of the onomatophore, it might turn out a valid name.

The original description of Hyperolius laticeps by Ahl (1931) is rather detailed, giving morphological description of all body parts, colour characters and a simple drawing. We examined the holophoront (holotype) of the species deposited in the Berlin Museum (ZMB 46529, sex not determined; detailed description in Appendix 1). It is a small, juvenile or subadult frog (SVL 14.2 mm), with a slender body, and a very flattened head forming a dermal fold on snout, probably from squeezing it when fixed. The head width of this specimen is relatively larger than in all other specimens of Hyperolius measured for this study, probably due to the compacting. The snout is rounded, the tympanum is poorly distinct. The tibia represents 42% of SVL, which falls within the variation of the Hyperolius specimens measured. A small webbing is present on fore limbs. Webbing on feet is moderate, leaving two and half phalanges free (webbing formula: I 1 ½ – 2 II 1 ½ – 2 III 2 – 2 ½ IV 2 ½ – 1 ½ V). The tips of toes bear distinctly enlarged discs with circumventral grooves. The skin is evenly smooth throughout back and flanks; this also can be linked to poor conservation. Belly and chest are granular. The dorsal colour pattern is weak but it corresponds to the figure of Ahl, showing a dark interorbital triangle, large bands on shoulder and pelvic region.

Recently Hyperolius sylvaticus was mentioned from Togo (Yégué) ( Hillers et al. 2009; this paper). This locality is only about 50 km from Sotouboua, where the holophoront of H. laticeps could have been collected, and it is far more to the North than the other occurrences of H. sylvaticus . Considering that the dorsal pattern of H. laticeps is similar to the banded morph of the dorsal patterns observed in H. sylvaticus , it is possible that H. laticeps might be taxonomically close to H. sylvaticus .

Three subspecies were recognised by SchiØtz (1967) in Hyperolius sylvaticus based on morphological characters: Hyperolius sylvaticus sylvaticus SchiØtz, 1967 , Hyperolius sylvaticus ivorensis SchiØtz, 1967 and Hyperolius sylvaticus nigeriensis SchiØtz, 1967 . Relatively few specimens of these subspecies are known, and only for four vouchers (two from Ghana, two from Côte d’Ivoire) molecular data are available; one comes from the onymotope of H. sylvaticus .

SchiØtz (1967, 1999) published photos of the three subspecies and a table summarizing the characters allowing to separate them. The three taxa show two kinds of dorsal colour patterns composed of an interorbital triangle, in contact with a shoulder band, the lumbar band being either separated from this pattern (H. s. ivorensis, H. s. nigeriensis ) or in contact by a narrower band (H. s. sylvaticus ). Furthermore, H. s. nigeriensis can be distinguished by the presence of a dark band on the side of the head behind the eyes, absent in H. l. ivorensis. SchiØtz (1967, 1999) described differences between the subspecies in adult size, H. s. nigeriensis being distinctly lager than the other subspecies.

Considering the holophoront of H. laticeps , the drawing of the specimen shows three dorsal bands, the interorbital and the shoulder band linked but the lumbar band separated. In the specimen the three bands are recognisable but the link is not observable any more. Ahl (1931) mentioned a dark band on the canthus rostralis filling the loreal region, but in the holotype no such band can now be observed on the tympanic region, behind the eyes.

MORPHOMETRY

We tried to test the generic and specific allocation of the holophoront specimen of Hyperolius laticeps by using a multivariate approach ( Ohler 1999). For this, 77 specimens of Hyperolius and Leptopelis were included in a Principal Component Analysis using 28 morphometric characters corrected for size. The result shows that the specimen ZMB 46529 clearly falls in the proximity of other Hyperolius species ( Fig. 8 ), and not with Leptopelis species. Concerning the differentiation at the species level, the scatterplots of the species largely overlap in the diagram, which is rather normal in such analyses bearing on closely related congeneric species ( Ohler et al. 2011). Factor 1 of the PCA ( Table 2 ) shows large values for the head measurements which might be correlated to the head measurements, modified by squeezing, of the H. laticeps specimen.

As the morphometrical results are not conclusive, we recommend to proceed molecular analyses on the holophoront of Hyperolius laticeps , including topotypical material of West African Hyperolius , in particular Hyperolius picturatus complex, to allow taxonomic identification. As Hyperolius laticeps is an early described species it might be potentially a senior homonym, and thus a valid name.

Figures

FIG. 7. — Hyperolius laticeps Ahl, 1931: 69. Onomatophore: holophoront (holotype) by monophory, ZMB 46529,juvenile frog, SVL 14.2 mm. Dorsal and ventral view of body, lateral view of head.

FIG. 8. — Scatterplot of Factor 2 ad 3 of Principal component analysis including 28 size corrected variables (compare Table 2). With green signs, Leptopelis Günther, 1859 species; yellowish, reddish or violet signs, Hyperolius Rapp, 1842 species.