Mini, Scherz & Hutter & Rakotoarison & Riemann & Rödel & Ndriantsoa & Glos & Roberts & Crottini & Vences & Glaw, 2019

Scherz, Mark D., Hutter, Carl R., Rakotoarison, Andolalao, Riemann, Jana C., Rödel, Mark-Oliver, Ndriantsoa, Serge H., Glos, Julian, Roberts, Sam Hyde, Crottini, Angelica, Vences, Miguel & Glaw, Frank, 2019, Morphological and ecological convergence at the lower size limit for vertebrates highlighted by five new miniaturised microhylid frog species from three different Madagascan genera, PLoS ONE 213314, pp. 1-45 : 8-12

Mini gen. nov.

urn:lsid:zoobank.org:act:67171236-00A2-428B-8194-584BF52E84E6

( Figs 2–9 , Table 1)

Type species. Mini mum sp. nov.

Contents. Mini mum sp. nov., M. scule sp. nov., and M. ature sp. nov.

Etymology. The genus name is derived from English prefix ‘mini-’, denoting a small version of an object. We treat this name as an arbitrary combination of letters in the sense of the

International Code of Zoological Nomenclature Articles 30.1.4.1 and 30.2.2, and we assign it the feminine gender. We have searched all available taxonomic databases and could not find any evidence that this name has ever been used to refer to a genus of animals, and we therefore conclude that it is available.

Diagnosis. Diminutive terrestrial frogs (adult SVL 8.2–14.9 mm), assigned to the Madagascar-endemic subfamily Cophylinae on the basis of divided vomers, procoelous vertebral column, divided sphenethmoids, and genetic affinities. Skin smooth to slightly granular, occasionally iridescent. A lateral colour border is present but varies in intensity among species. Highly reduced fingers and toes, fusion or loss of carpal 2, and paedomorphic skull morphology: laterally displaced narrow nasals, teeth absent from vomer, in some species present on the maxilla and premaxilla, otic capsule sometimes dorsally ossified, brain case comprising most of the skull’s length and width.

All members of the genus Mini gen. nov. resemble miniaturised to extremely miniaturised members of the genus Stumpffia . However, all species can be distinguished from Stumpffia on the basis of their curving clavicles and a fused or lost carpal 2. In the species accounts below, we provide detailed distinctions from Stumpffia relevant to each species.

Justification. The erection of the genus Mini is justified by significant genetic differentiation from all other major cophyline lineages (see Fig 1 ), by the fact that it does not form a monophyletic group with the genus Stumpffia , and furthermore by the strong morphological differences (including but not restricted to the much smaller size) to all species of its sister clade, Plethodontohyla . The following characters distinguish the genus from all Plethodontohyla species, including juveniles: digital reduction of the fingers and toes (vs no reduction), laterally displaced and reduced nasals (vs large nasals situated anterior to frontal), parasphenoid cultriform process shorter than frontoparietals (vs roughly equal in length to the

frontoparietals) and considerably narrower than alary processes (vs as wide or wider), vomerine teeth absent (vs present), carpal 2 absent (vs present). Uncorrected p-distances between Mini and Plethodontohyla range from 8.3–13.3% in the 3’ fragment of 16S rRNA analysed here, and they have been found to be sister to Plethodontohyla in all phylogenetic analysis since their first inclusion in genetic datasets [ 15, 17, 20, 22] (except the DNA barcoding study of Vieites et al. [ 40], where they were placed at the base of Rhombophryne + Stumpffia + Anilany , but that study lacks any resolution at deep nodes, and was not intended to provide phylogenetic hypotheses at deep levels).

Distribution. The genus Mini is apparently endemic to low-elevation habitats (0–350 m a. s. l.) of southeastern Madagascar ( Fig 3 ).

Figures

Fig 1. Stylised representation of the latest phylogeny of the microhylid subfamily Cophylinae. Based on the phylogenetic tree of Tu et al. [20] (reconstructed from a concatenated multi-gene DNA sequence data set) with numerous nomenclatural updates. See that paper for support values and phylogenetic context. The sister species of Rhombophryne proportionalis sp. nov. is an undescribed candidate species (R. sp. Ca7) that is not included in this phylogeny; its taxonomy will be treated elsewhere. Taxa highlighted in red are those described herein. Inset photos show a selection of the new species described herein, and representatives of the other small-bodied genera, Stumpffia and Anilany. Inset photos are not to scale. https://doi.org/10.1371/journal.pone.0213314.g001

Fig 2. Holotypes of the new species described in this paper and their hands. Whole specimens in dorsal (left) and ventral (right) view. Hand images not to scale. https://doi.org/10.1371/journal.pone.0213314.g002

Fig 3. Currently known localities of the new taxa described in this paper. The base map is USGS SRTM 1-Arc second digital elevation model. https://doi.org/10.1371/journal.pone.0213314.g003

Fig 4. Mini mum gen. et sp. nov. in life and its habitat in Manombo Special Reserve. (a-c) ZSM 861/2014, holotype, in (a) anterolateral view on a thumbnail, (b) dorsolateral view on a leaf, (c) ventral view. (d, e) ZSM 862/2014, paratype, in (d) ventral view, and (e) lateral view on a thumbnail. (f, g) ZMB 83194, paratype, in (f) dorsolateral view, and (g) ventral view. (h) ZMB 81993, paratype, in dorsolateral view. (i) ZMA 20172 in posterodorsolateral view. (j) Habitat of the new species in Manombo Special Reserve. https://doi.org/10.1371/journal.pone.0213314.g004

Fig 5. One-second spectrograms and oscillograms of the calls of the new species described here. Insets represent the respective species but not the calling specimens. (a) Mini mum gen. et sp. nov., paratype ZMB 81993 from Manombo, (b) Mini scule gen. et sp. nov., ZSM 265/2018 from Sainte Luce, (c) Rhombophryne proportionalis sp. nov., part of a call (note series) of a specimen from Bepia campsite, Tsaratanana (not collected), (d) Anodonthyla eximia sp. nov., specimen not collected, from Maharira (Ranomafana). https://doi.org/10.1371/journal.pone.0213314.g005

Fig 6. Osteology of Mini mum gen. et sp. nov. holotype (ZSM 861/2014). (a-c) Whole skeleton in (a) dorsal, (b) lateral, and (c) ventral view. (d-g) Skull in (d) lateral, (e) ventral, (f) anterior, and (g) dorsal view. (h) Foot in ventral view. (i) Hand in ventral view. Abbreviations for all osteological figures: angspl, angulosplenial; col.pip, pars interna plectra of columella; col.pmp, pars media plectra of columella; cpl(s), carpal(s); den, dentary; exoc, exoccipital; exoc.occ, occipital condyle of exoccipital; fpar, frontoparietal; max, maxilla; max.fp, facial process of maxilla; mmk, mentomeckelian; n, nasal; n.mp, maxillary process of nasal; npl, neopalatine; oc, otic capsule; prsph. ap, parasphenoid alary process; prsph.cp, parasphenoid cultriform process; prsph.pmp, parasphenoid posteromedial process; pmx, premaxilla; pmx.ap, premaxilla ascending process; pmx.lp, premaxilla lateral process; pmx.pp, premaxilla palatine process; povom, postchoanal portion of vomer; pro, prootic; prvom, prechoanal portion of vomer; pt.ar, pterygoid anterior ramus; pt.mr, pterygoid medial ramus; pt.vr, pterygoid ventral ramus; qj, quadratojugal; smx, septomaxilla; spheth, sphenethmoid; sq. or, squamosal otic ramus; sq.vr, squamosal ventral ramus; sq.zr, squamosal zygomatic ramus; tsl(s), tarsals; vt, vomerine teeth. https://doi.org/10.1371/journal.pone.0213314.g006

Fig 7. Mini scule gen. et sp. nov. in life and its habitat in Sainte Luce Reserve. (a, b) ZSM 5943/2005, holotype, in (a) dorsolateral and (b) ventral view. Black lines in the two pictures are scanning artefacts from damaged analogue slides. (c) Probably ZSM 5942/2005, paratype, in dorsolateral view. (d-f) ZSM 265/2018 (SHR 09112018) in (d) dorsal, (e) dorsolateral, and (f) ventral view. Note the numerous pink cf. Endotrombicula mites on the abdomen and legs. (g) Habitat in Sainte Luce Special Reserve. (h, i) Mini cf. scule from Nahampoana, ZFMK 53775 in (h) lateral and (i) ventral view. https://doi.org/10.1371/journal.pone.0213314.g007

Fig 8. Osteology of Mini scule gen. et sp. nov. holotype (ZSM 5943/2005). (a, b) Whole skeleton in (a) dorsal and (b) ventral view. (c-f) Skull in (c) lateral, (d) ventral, (e) anterior, and (f) dorsal view. (g) Foot in ventral view. (h) Hand in ventral view. For abbreviations, see Fig 6. https://doi.org/10.1371/journal.pone.0213314.g008

Fig 9. Osteology of Mini ature gen. et sp. nov. holotype (ZSM 86/2004). (a-c) Whole skeleton in (a) dorsal, (b) lateral, and (c) ventral view. (d-g) Skull in (d) lateral, (e) ventral, (f) anterior, and (g) dorsal view. (h) Foot in ventral view. (i) Hand in ventral view. For abbreviations, see Fig 6. https://doi.org/10.1371/journal.pone.0213314.g009