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

Abstract

The genus Scaphiophryne (Anura: Microhylidae) contains at least nine species that, together with their probable sister genus Paradoxophyla, form the Madagascar-endemic subfamily Scaphiophryninae. Scaphiophryne are robust burrowing frogs with explosive breeding behavior and are characterized by a unique larval morphology, being intermediate between that of filter-feeding and generalized tadpole types. Based on tadpole morphology, the nominal subgenus Scaphiophryne can be distinguished from the subgenus Pseudohemisus, a clade occurring in arid biomes with a largely unsolved taxonomy and nomenclature. Here we combine a comprehensive molecular phylogeny of all scaphiophrynines based on five mitochondrial and two nuclear genes with a re-examination of the name-bearing type specimens of the seven species-level nomina assignable to the subgenus Pseudohemisus. Our molecular phylogeny supports monophyly of the two subgenera and assigns the enigmatic S. matsoko to the subgenus Scaphiophryne. In this subgenus, our analysis confirms all currently accepted species as independent evolutionary lineages based on concordant differentiation in mitochondrial and nuclear genes, and provides evidence for a combination of low mitochondrial divergence, distinct nuclear divergence, and high nuclear heterozygosity. Yet, contrary to previous hypotheses, we do not find evidence of ongoing hybridization. In the subgenus Pseudohemisus we find support for three clearly delimited species-level lineages, one of which contains two deep conspecific lineages that warrant further study. To stabilize the taxonomy in this subgenus, and considering the very poor state of preservation of several type series and the heterogeneity of some of them, we here designate lectotypes for the nomina: Hemisus obscurus Grandidier, 1872; Calophrynus calcaratus Mocquard, 1895; Pseudohemisus verrucosus Angel, 1930; Pseudohemisus longimanus Angel, 1930; and Pseudohemisus longimanus var. melanopleura Angel, 1934. Taxonomically, we accept Scaphiophryne brevis (Boulenger, 1896) as a well-defined species; restrict S. calcarata (Mocquard, 1995) to the southern lineage of the S. calcarata complex; resurrect Hemisus obscurus Grandidier, 1872 (previously considered to be a dubious name or nomen inquirendum) as Scaphiophryne obscura to refer to the western and north-western lineage of the S. calcarata complex; consider Pseudohemisus verrucosus Angel, 1930 as junior synonym of Scaphiophryne brevis; and consider Pseudohemisus longimanus Angel, 1930 and Pseudohemisus longimanus var. melanopleura Angel, 1934 as junior synonyms of Scaphiophryne obscura. Finally, to accelerate taxonomic progress, we (i) outline a set of criteria by which such old and ambiguous nomina can be applied to known lineages, (ii) suggest that the International Code of Zoological Nomenclature should slightly broaden the conditions under which neotypes are to be designated, and (iii) propose to redouble discussions on the introduction of the concept of the epitype to zoology.

Uncovering the herpetological diversity of small forest fragments in south-eastern Madagascar (Haute Matsiatra)

“…2O Scaphiophryne calcarata belongs to the subgenus Pseudohemisus. A recent study assigned the lectotype of five nomina (including Calophrynus calcaratus Mocquard, 1895) (Scherz et al 2021). This taxonomic proposal, together with the analysis of newly-collected material, enabled the restriction of the lineage of Scaphiophryne calcarata to the southern and south-western portion of the Island.…”

“…), are assigned to this lineage. They were included in Scherz et al (2021) contributing to extend the known distributional range by ca. 180 km in a northern direction.…”

An inordinate fondness for inconspicuous brown frogs: integration of phylogenomics, archival DNA analysis, morphology, and bioacoustics yields 24 new taxa in the subgenus Brygoomantis (genus Mantidactylus) from Madagascar

“…org, accessed 22 December 2021). Indeed, we advocate for conservative approaches that make as much use of existing names as possible (Scherz et al 2021), and employ a parsimony of taxonomic changes (Scherz et al 2017b), to avoid overloading the entire community of biological scientists with new, unnecessary nomenclatural changes (which also discredit taxonomy and taxonomists).…”

“…First, the assignment of names must be clarified. this can be done in a variety of ways, but two chief components that we use here are (i) logic-and plausibility-based argumentation based on all information contained in the original description and from the type specimens themselves, while maintaining a 'parsimony of taxonomic change' (Scherz et al 2017b(Scherz et al , 2021, and (ii) cutting-edge 'museomic' methods for sequencing 'archival' DNA from types, in our case using the 'barcode fishing' method pioneered in Mantidactylus by rancilhac et al (2020) and Scherz et al (2020).…”