Hemisus obscurus Grandidier, 1872

Scherz, Mark D., Schmidt, Luca, Crottini, Angelica, Miralles, Aurélien, Rakotoarison, Andolalao, Raselimanana, Achille P., Köhler, Jörn, Glaw, Frank & Vences, Miguel, 2021, Into the Chamber of Horrors: A proposal for the resolution of nomenclatural chaos in the Scaphiophryne calcarata complex (Anura: Microhylidae), with a new species-level phylogenetic hypothesis for Scaphiophryninae, Zootaxa 4938 (1), pp. 392-420 : 405-406

Hemisus obscurus Grandidier, 1872

Name-bearing type: Lectotype by present designation, MNHN 1895.280 , from “Côte N. O. de Madagascar ” according to the original description.

Originally, there were four syntypes, all catalogued under MNHN 1895.280 ; one of these specimens today has an attached label with the number 1895.280 (here designated as lectotype, see below), and two other original syntypes (now paralectotypes) probably correspond to 280A and 280B (see below). The fourth specimen (according to the MNHN catalogue used for a skeleton preparation) was not examined as it could not be retrieved in the MNHN collection. The type locality “Côte N. O. de Madagascar ” means “Côte Nord Ouest”, i.e., the north-west coast .

Hemisus obscurus , the type species of the subgenus Pseudohemisus , is the earliest available name for a Malagasy microhylid species from western Madagascar and therefore must be a valid taxon for reasons of priority. However, probably due to the short description and bad state of preservation of the types, the species has been considered as dubious by Blommers-Schl̂sser & Blanc (1991) and not further discussed in subsequent publications. In fact, Mocquard (1895) already stated that the types were in very poor condition when he erected Pseudohemisus as new genus name for this taxon.

Upon examination in 2020, the three syntypes of Hemisus obscurus were in an extremely poor state of preservation. The largest of the specimens ( SVL 23.7 mm; see Table 1) bears the label 1895.280; two additional labels 1895.280A and 280B are included in the same jar and probably refer to the other two specimens, which bear no labels and which measure 19.9 mm and 16.1 mm in SVL, respectively. Because these specimens are smaller, probably not adults, bear no labels, and are in an even worse state of preservation, the largest specimen with the label 1895.280 is here designated as lectotype to stabilize this nomen .

Morphology. Only a few measurements could be taken due to the bad state of preservation; these are included in Table 1. The enlarged inner metatarsal tubercle typical for Scaphiophryne , and the size and shape of subarticular tubercles, is not recognizable in the lectotype, probably because most of the skin around the feet is destroyed ( Fig. 9 ). However, it is just possible recognize a tarsal tubercle in the lectotype, which is typical for Scaphiophryne , and the enlarged inner metatarsal tubercle is still faintly visible in one of the paralectotypes. Furthermore, the triangular shape of the head, becoming distinctly narrower towards the snout, which is rather truncate in dorsal and ventral views, and the absence of vomerine and maxillary teeth, indicate that the lectotype and the two paralectotypes indeed are Scaphiophryne . The head of the lectotype bears what might be the remains of a light vertebral line as is typical for most specimens of the S. calcarata complex (e.g., Glaw & Vences 2007).

The designated lectotype also agrees osteologically with traits of the subgenus Pseudohemisus based on the deepened septomaxilla, T-shaped squamosal, ossified and anteriorly extended sphenethmoid, maxillary and vomerine teeth absent, non-divided vomer (divided in Cophylinae ), sacral diapophysis flattened and broadened (as diagnostic for microhylids), vertebral column diplasiocoelous, terminal phalanges of fingers and toes knobbed and not T-shaped as in species in subgenus Scaphiophryne with expanded finger and toe tips, and pectoral girdle without ossified sternum and omosternum but with ossified clavicles ( Fig. 10 , Supplementary Figs S2–S 3 ).

Assignment. The type locality of Hemisus obscurus is, rather imprecisely, the north-west coast of Madagascar. In this region, no frogs of the lineage assigned to S. brevis (see below) occur, and therefore it is clear that the name obscurus should be assigned to a lineage of the S. calcarata complex. Hence, we apply the name Scaphiophryne obscura ( Grandidier, 1872) to the north-western/western lineage of the S. calcarata complex, i.e., to the form called Scaphiophryne calcarata A in Glaw & Vences (2007) and Scaphiophryne sp. 2 in Vieites et al. (2009).

Figures

FIGURE 2. Haplotype networks based on DNA sequences of two nuclear genes, POMC (310 bp) and RAG-1 (788 bp) for species of Scaphiophryne and Paradoxophyla. Small black circles represent additional mutational steps between identified haplotypes. Colors of taxa correspond to those in Fig. 1.

FIGURE 3. Individuals in life of the three species of Scaphiophryne in the subgenus Pseudohemisus according to the classification proposed in the present paper: Scaphiophryne brevis from Ifaty (A–E), Kirindy (F–G) and Isalo (H); S. calcarata from Pic St. Louis near Tolagnaro (I–K), Ambalavao (L), Isalo (Ilakaka) (M–N), Sakaviro (O) and near Anja (P); S. obscura from Isalo (Q), Kirindy (R–V), Ankarafantsika (W), and Bongolava Plateau (X). Photos by F. Glaw, J. Lobon-Rovira, A. Miralles, G. M. Rosa, and M. Vences.

FIGURE 9. Photographs of the details of morphology of type specimens of the nomina in the genus Scaphiophryne (subgenus Pseudohemisus) except the holotype of S. brevis, showing feet (left column) and hands (middle column) in ventral view, and the head (right column) in lateral view.

FIGURE 10. Micro-CT scans of the name-bearing type specimens of nomina in the subgenus Scaphiophryne (Pseudohemisus) except the holotype of S. brevis: skulls in dorsal, ventral and lateral views.