Mantidactylus incognitus, Scherz & Crottini & Hutter & Hildenbrand & Andreone & Fulgence & Köhler & Ndriantsoa & Ohler & Preick & Rakotoarison & Rancilhac & Raselimanana & Riemann & Rödel & Rosa & Streicher & Vieites & Köhler & Hofreiter & Glaw & Vences, 2022

Scherz, Mark D., Crottini, Angelica, Hutter, Carl R., Hildenbrand, Andrea, Andreone, Franco, Fulgence, Thio Rosin, Köhler, Gunther, Ndriantsoa, Serge Herilala, Ohler, Annemarie, Preick, Michaela, Rakotoarison, Andolalao, Rancilhac, Loïs, Raselimanana, Achille P., Riemann, Jana C., Rödel, Mark-Oliver, Rosa, Gonçalo M., Streicher, Jeffrey W., Vieites, David R., Köhler, Jörn, Hofreiter, Michael, Glaw, Frank & Vences, Miguel, 2022, 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, Megataxa 7 (2), pp. 113-311 : 224-226

Mantidactylus incognitus sp. nov.

Identity and justification.—This enigmatic lineage is phenotypically assigned to the M. betsileanus clade and has been considered as unconfirmed candidate species M. sp. 34 by Vieites et al. (2009), and M. sp. Ca34 by Perl et al. (2014). Only a minimal amount of information on this lineage is available. It is phylogenetically sister to M. betsileanus in our FrogCap analysis ( Fig. 5 ) with which it also shares Rag-1 haplotypes, and it occurs parapatrically but in close geographic proximity with this species. We here consider it as distinct species due to its highly divergent mitochondrial DNA sequences (6.2–7.6% 16S divergence to M. betsileanus ), and the distinct dorsal ridges, and tubercles above the eye seen in the holotype (absent or more weakly expressed in M. betsileanus ). Furthermore, also the FrogCap analysis supports a substantial genomic divergence, given the long branch length separating this lineage from M. betsileanus .

Mantidactylus incognitus sp. nov. is the only species of Brygoomantis for which no photos in life are available (same applies also to one subspecies, M. manerana antsanga ssp. nov.; see below).

Holotype.— ZSM 669/2009 ( ZCMV 8945 ), probably a subadult female, collected by P.-S. Gehring, F.M. Ratsoavina, and E. Rajeriarison on 22 April 2009 at Mahanoro (19.6536°S, 048.7780°E), Antsinanana Region , Madagascar. A 16S barcode sequence of the holotype was obtained in this study and was included in the analysis.

Paratypes.—A total of two paratypes : UADBA uncatalogued ( MV 2001.1156 = 2002.G9), specimen of unknown sex and maturity, collected by M. Vences on 26– 27 November 2001 in Vohidrazana (precise coordinates unavailable); MRSN A6694 ( RJS 1801 = ACZC 4189 ), adult male, collected by J.E. Randrianirina at Anivorano Est (18.7638°S, 048.9468°E, 60 m a.s.l.) .

Additional material.—Two series of tadpoles, ZSM 1042/2004 and ZSM 1043/2004, from Vohidrazana.

Diagnosis.— Mantidactylus incognitus sp. nov. is a member of the M. betsileanus clade as revealed by the phylogenomic analysis, representing the sister species of M. betsileanus . See Table 4 for a list of diagnostic morphological characters. The combination of a relatively small body size in males (SVL 27 mm), dorsal skin with several distinct dorsolateral ridges and supraocular tubercles, reduced webbing (one phalanx of fifth toe free of web), absence of white spots on flanks, and presence of a white marking on snout tip, distinguishes M. incognitus sp. nov. from species of all other clades ( Table 4 ). Within the M. betsileanus clade, the new species differs from M. noralottae by smaller body size and presence of a distinct white marking on snout tip; and from M. betsileanus , M. noralottae , and M. tripunctatus by distinct dorsal ridges (in addition to the dorsolateral ridges) and strongly expressed supraocular tubercles. For a distinction from the other new species described herein, see the respective species accounts. A full list of molecular diagnostic sites in the 16S gene of M. incognitus sp. nov. in pairwise comparisons to all other Brygoomantis species is provided as Supplementary appendix.

Description of the holotype.—Specimen in moderate state of preservation (soft fixation); probably a subadult female with rudimentary ovary based on gonad examination. Some muscle tissue removed from left thigh ( Fig. 33 ), and a longitudinal lateroventral cut made for gonad examination. Some skin missing from left thigh and shank dorsally. Body relatively slender. Head as wide as body. Snout rather truncate in dorsal and lateral views which might be a preservation artefact. Nostrils directed laterally, slightly protuberant, nearer to tip of snout than to eye. Canthus rostralis weakly recognisable, slightly concave; loreal region slightly concave. Tympanum distinct, rather small, rounded, horizontal diameter of tympanum61%of horizontal eye diameter.Supratympanic fold distinct, beginning straight behind eye, with gentle ca 45° bending midway towards forelimb insertion. Tongue ovoid, distinctly bifid. Maxillary teeth present. Vomerine teeth form two small rounded aggregations, positioned posterolateral to choanae. Choanae rounded. Subarticular tubercles single. Inner and outer metacarpal tubercles present. Fingers without webbing. Relative length of fingers: I<II<IV<III. Finger discs slightly enlarged.

Nuptial pads absent. Foot slightly shorter than tibia (95%). Lateral metatarsalia separated. Inner metatarsal tubercle present. Outer metatarsal tubercle small but clearly recognisable. Webbing formula: 1(1), 2i(1.5), 2e(1.5), 3i(2), 3e(1), 4i(2), 4e(2.5), 5(1). Relative length of toes: I<II<V<III<IV. Skin on the upper surface with numerous discontinuous but distinct longitudinal ridges, one of these extending into supraocular region. A series of distinct supraocular tubercles. Ventral side smooth. Small rudimentary femoral glands visible.

Colour in preservative: dorsally light brown to beige, with a slightly darker shade medially on dorsum. Several of the dorsal ridges are lined with dark brown. Distinct dark crossbands on limbs. A dark band between eyes and a relatively small white patch on snout tip. Ventrally light beige with distinct and contrasted brown pattern on throat and chest. Throat with disctinct, interrupted median light stripe. Lower lips ventrally with alternating light-dark pattern. Colour of holotype in life not documented.

Variation.—Variation in measurements is given in Table 7. Colouration in life unknown. Insufficient number of reliably sexed, adult specimens available to assess sexual dimorphism.

Natural history.—Very little is known on the habits of this species. Tadpoles at Vohidrazana were collected from a stream in degraded rainforest.

Calls.—The call of this species is unknown.

Tadpoles.— The tadpole of M. incognitus was described under the name ‘ Mantidactylus sp. aff. betsileanus “Vohidrazana”’ by Knoll et al. (2007).

Distribution.— Distributed in a rather small area of the Northern Central East ( Fig. 7 ). This species is known from Anivorano Est, Bemandrevo, Andekaleka, Mahanoro, Sahafina, and Vohidrazana. Elevation range: 10–810 m a.s.l.

Etymology.—The Latin adjective incognitus, meaning ‘unknown’, referring to the extremely poor knowledge we have on this genetically distinct species.

Figures

FIGURE 5. Maximum-Likelihood tree based on a partitioned analysis of 12,818 nuclear-encoded markers obtained via the FrogCap strategy, calculated with IQ-tree, for 58 representative individuals of species-level lineages in the subgenus Mantidactylus (Brygoomantis). Note that three species are missing from this analysis (M. bletzae sp. nov., M. marintsoai sp. nov., and M. riparius sp. nov.) and the identity of the two samples of M. katae sp. nov. in this tree is uncertain. For those lineages that previously (Perl et al. 2014; Vieites et al. 2009) had candidate species numbers assigned, these are reported in parenthesis after the name used in the classification proposed herein. All branches were fully supported by SH-like approximate likelihood ratio tests with 1000 pseudoreplicates (100% support, symbolized by black dots at nodes).The tree was rooted with Mantidactylus grandidieri (subgenus Mantidactylus) as outgroup (removed from graphical representation for better visualization of ingroup relationships), with the inclusion of M. melanopleura (subgenus Chonomantis) as hierarchical outgroup. Red arrows in the M. curtus clade indicate the two reticulation events detected by a Phylonetworks analysis performed separately for this clade (note that the topology recovered by this analysis in the Phylonetworks analysis differs in the position of M. bourgati; see original results of the Phylonetworks analysis in Zenodo repository, DOI 10.5281/zenodo.668741

FIGURE 7. Mantidactylus subgenus Brygoomantis species distribution based on verified records, divided by clade (Mantidactylus stelliger sp. nov. is presented alongside the inaudax clade for practicality). Colours for species correspond to those in Figs 2 and 4. Inset map shows the geographic regions of Madagascar identified by Boumans et al. (2007), referred to throughout the text.

FIGURE 33. Preserved holotype specimens of newly named species in the M. betsileanus clade. Scale bars equal 5 mm.