Anodonthyla eximia, 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 : 33-37

publication ID	https://doi.org/ 10.1371/journal.pone.0213314
DOI	https://doi.org/10.5281/zenodo.5689493
persistent identifier	https://treatment.plazi.org/id/03F887F6-FFB3-0A6C-FD8B-0520DF846F07
treatment provided by	Plazi
scientific name	Anodonthyla eximia
status	sp. nov.

Treatment

Anodonthyla eximia View in CoL sp. nov.

urn:lsid:zoobank.org:act:2C419E74-C13D-447D-BDCF-312324515EAE

( Figs 1 View Fig 1 , 2 View Fig 2 , 3 View Fig 3 , 5 View Fig 5 , 12 View Fig 12 and 13 View Fig 13 , Tables 1 and 2 View Table 2 )

Remark. This species was previously listed as A. sp. Ranomafana (Maharira) [ 24], A. sp.

Ca04 Ranomafana (ZCMV204) [ 15] and Anodonthyla View in CoL sp. 4 Ranomafana [ 20].

Holotype. ZMA 20246 ( ZCMV 204 , GenBank accession number GU177052 View Materials and FJ559111 View Materials for the 5’ and 3’ fragments of the 16S rRNA gene, respectively, and GU177063 View Materials for the cox1 gene), an adult male specimen (vocal sac inflated when collected) collected from a campsite at the base of Maharira mountain (21.3258˚S, 47.4025˚E, approx. 1248 m a.s.l.) in Ranomafana National Park, Vatovavy-Fitovinany Region, former Fianarantsoa province, southeastern Madagascar on 25 January 2004 by M. Vences, I. de la Riva, and E. Rajeriarison.

Diagnosis. An extremely miniaturised frog assigned to the genus Anodonthyla on the basis of the possession of a large, cultriform prepollex, T-shaped terminal phalanges, absence of postchoanal vomer, and by its genetic affinities. It is separated by uncorrected p-distances of 9.3–17.0% in the analysed 3’ fragment of the 16S rRNA gene from all other members of the genus Anodonthyla .

Anodonthyla eximia sp. nov. is characterised by the unique combination of the following characters (n = 1 male specimen): (1) male SVL 11.3 mm; (2) ED/HL 0.45; (3) HW/SVL 0.31; (4) FARL/SVL 0.30; (5) TIBL/SVL 0.39; (6) HIL/SVL 1.34; (7) finger 1 highly reduced, other fingers small; (8) toe 1 absent, toes 2 and 5 quite reduced; (9) maxillary and premaxillary teeth absent; (10) vomerine teeth absent; (11) lateral colour border absent; (12) black inguinal spots absent; (13) postchoanal vomer absent; (14) nasal subrectangular with an acuminate maxillary process, not displaced; (15) quadratojugal-maxilla contact absent; (16) zygomatic ramus of squamosal short, thin, and anterodorsally oriented; (17) clavicles present, curving with simple lateral articulations, medially bulbous; (18) prepollex cultriform, longer than first metatarsal; (19) carpal 2 present; (20) finger phalangeal formula 1-2-3-3; (21) toe phalangeal formula 2-2- 3-4-3; (22) single-note, unpulsed calls, not emitted in series; (23) weakly frequency modulated calls; (24) call dominant frequency 8406 ± 78 Hz (n = 5); (25) call duration 59.6 ± 6.5 ms

(n = 5); (26) inter-call interval 3749.0 ± 1149.9 ms (n = 4).

This species is considerably smaller than all other Anodonthyla species (11.3 mm vs 15–34 mm), and as such is only possible to confuse with juveniles of its congeners. In addition to its small size, it can be distinguished from all other Anodonthyla species by the absence of flared crests on the humerus in adult males. Among similarly sized adult frogs in Madagascar, it can be distinguished by the possession of a large inner metacarpal tubercle with a large, cultriform prepollex (present only in male Anodonthyla , much smaller in all other species except Anilany , where it is broad and triangular instead of cultriform), and a laterally displaced neopalatine not in contact with the sphenethmoid or vomer (neopalatine either in contact with sphenethmoid or in contact with vomer in all other species; in some species of Stumpffia , the neopalatine is lost, unpublished data).

Holotype description. Specimen in a good state of preservation, a piece of the right thigh removed as a tissue sample. Body oblong; head wider than long, narrower than the body width; snout rounded in dorsal and lateral view; nostrils directed laterally, not protuberant, closer to eye than to tip of snout; canthus rostralis rounded, straight; loreal region concave, vertical; tympanum indistinct, round, about 46% of eye diameter; supratympanic fold weak, not raised, straight from posterior corner of eye to axilla; tongue long, thin, attached anteriorly, not notched; maxillary teeth absent, vomerine teeth absent; choanae oblong, very small. Forelimbs relatively broad; subarticular tubercles indistinct, single; outer metacarpal tubercle

small, indistinct, single; inner metacarpal tubercle large and distinct, bulging outward strongly, underlain by cultriform prepollex; hand without webbing; all fingers short, first highly reduced and only marginally longer than the prepollex; relative length of fingers 1 <2 = 4 <3, fourth finger equal in length to second; tip of third finger marginally expanded, other fingers not expanded into discs. Hind limbs robust; TIBL 39% of SVL; lateral metatarsalia strongly connected; inner metatarsal tubercle rounded, indistinguishable from first toe; outer metatarsal tubercle absent; no webbing between toes; first toe practically absent, second and fifth toes shortened; relative length of toes 2 <5 <3 <4; fifth toe distinctly shorter than third. Skin on dorsum smooth, without distinct dorsolateral folds. Ventral skin smooth.

After 13 years in 70% ethanol, the dorsum is pale brown with a faint darker brown chevron over the scapular region ( Fig 2 View Fig 2 ). The dorsal legs have faint dark brown crossbands, especially on the shanks. The dorsal colouration fades over the shanks to cream, which is continuous on the venter. The lateral head is dark brown, with a distinct border to the dorsum and flank formed by the supratympanic fold. The chin is a lighter brown than the dorsum but distinctly not the cream of the abdomen. The ventral legs are translucent cream. Colour in life as in preservative but more vibrant; the venter was slate grey with blue-cream flecks.

Bioacoustics. Calls recorded from an unknown specimen by M. Vences at 08h45, on 26 January 2004 at Maharira in Ranomafana National Park (21.3258˚S, 047.4025˚E, 1248 m a.s.l.) in the leaf litter of primary rainforest, referred to this species ( Fig 4D View Fig 4 , Table 2 View Table 2 ). The holotype and single known specimen of this species was collected during careful searches of the leaf litter from the exact spot where similar calls were heard, and upon capture, had an apparent partially inflated vocal sac. No other calls assignable to a miniature frog were heard in the area at this time in the morning. Assignment of the calls to this species therefore is the most likely hypothesis but remains tentative. The call bears remarkable resemblance to that of Stumpffia miery ( Table 2 View Table 2 ), which is also known from lower elevations in Ranomafana National Park, and detailed future field study will be required to confirm its assignment to Anodonthyla eximia sp. nov.

Calls were emitted as part of a large chorus in the early hours of the morning following cyclonic rainfall after the retreat of major flooding of the area. Calls consisted of a single note and were emitted at regular intervals without defined call series. Calls were weakly frequency modulated with an increase in pitch, but recording quality is too poor for detailed analysis. For approximate call parameters, see Table 2 View Table 2 .

Osteology ( Fig 13 View Fig 13 ). Based on ZMA 20246 (figured).

Cranium ( Fig 13 View Fig 13 D–13G). Shape and proportions. Skull short and rounded, longer than wide, widest at the bowing of the quadratojugal roughly in line with the anterior face of the prootic. Braincase proportionally broad, with an extremely short rostrum.

Neurocranium. Moderately ossified, otic capsules partly ossified. Sphenethmoid unossified. Prootic in dorsal contact with lateral flange of frontoparietal, ventral contact with parasphenoid alae, not approaching contralateral. Septomaxilla miniscule, very tightly curled, not further discussed due to low ossification and insufficient resolution. Columella (stapes) well ossified, pars media plectra (stylus) long and slightly curved, posteriorly and dorsally oriented toward the broadened, somewhat posteriorly oriented pars interna plectra (baseplate). Nasal narrow, retaining the shape of larger cophylines: subrectangular with an elongated, acuminate maxillary process that does not closely approach the maxillary pars facialis; displaced laterally, broadly separated from contralateral. Frontoparietal with rounded anterior edge, laterally rather straight-edged, with short lateral flange covering prootic, posteriorly strongly connected to exoccipital, lacking any dorsal process, separated from contralateral by a narrow gap with a small rhomboid facet at the level of the prootics, which may represent a pineal foramen.

Parasphenoid with narrow, rather straight-edged cultriform process and roughly equally broad perpendicular alae, considerably shorter than frontoparietals, in contact with exoccipitals posterodorsally, prootics dorsally along the edges of the alae, anteroventrally free; posteromedial process long but not participating in foramen magnum. Vomer lacking postchoanal portion (typical of Anodonthyla ); prechoanal portion strongly curved, bearing a small lateral ramus. Neopalatine simple and very thin, laterally displaced, not contacting any other ossified elements.

Maxillary arcade gracile, maxilla and premaxilla edentate, anterior extension of maxilla not exceeding lateral extent of premaxilla. Premaxilla with a narrow dorsal alary process rising laterally, pars palatina shallowly divided into a narrow palatine process and broad lateral process. Maxilla practically lacking a pars facialis and bearing a narrow pars palatina, its posterior tip acuminate and not contacting the quadratojugal, the lingual surface of the pars palatina contacting the anterior ramus of the pterygoid, which has taken over the articulation. Pterygoid with a short medial ramus, long and strongly curved anterior ramus, and broad posterior ramus, posteriorly calcified to the quadratojugal complex. Quadratojugal bowed laterally, rather short, broadly connected to the ventral ramus of the squamosal, bearing a small posteroventral knob, anteriorly dividing and with decreasing ossification, not connected to the maxilla; the articulation of the mandible is apparently somewhat fortified by the mineralisation of the posterior ramus of the pterygoid+squamosal+quadratojugal posteroventral knob. Squamosal with a slender, rather straight ventral ramus, thin, posterodorsally oriented otic ramus, and short, thin, anterodorsally oriented zygomatic ramus.

Mandible slim and edentate, largely unremarkable, with a weakly raised coronoid process on the angulosplenial. Mentomeckelians separated from the dentary, with small, poorly ossified hooked ventrolateral projections.

Posteromedial processes of hyoid proximally rounded without an obvious medial crista.

Postcranial skeleton ( Fig 13 View Fig 13 A–13C, 13H and 13I). Eight procoelous presacrals, all much broader than long, lacking neural spines, with round posterior articular processes, presacral I with a complete neural arch, presacrals II–IV with thicker and longer transverse processes than V–VIII. Sacrum with flared diapophyses, the leading and trailing edges roughly equally curved, the articulation type IIB sensu Emerson [ 42]. Urostyle bicondylar, long, broadening gently posteriorly, with a somewhat flared head and a low dorsal ridge.

Pectoral girdle without ossified prezonal or postzonal elements, with ossified clavicles. Clavicle thin and curved, with a simple lateral junction, equal in length to the coracoid, medially bulbous. Coracoid broad, flared laterally and strongly flared medially with a curving medial articular surface with the contralateral. Scapula robust, with a broad pars acromialis, the cleithral border straight. Cleithrum ossified for three-quarters the width of the scapular border, thickened anteriorly. Suprascapula unossified.

Humerus with a well-developed crista ventralis and no medial or lateral cristae. Radioulna slender with a distinct sulcus intermedius. Carpals composed of radiale, ulnare, element Y, prepollex, carpal 2, and a large post-axial element formed by carpals 3–5. Prepollex extremely long and acuminate, longer than first metacarpal. Finger phalangeal formula is reduced (1-2- 3-3), and the terminal phalanx of the first finger small and columnar, others bearing T-shaped knobs.

Pubis ossified; iliac shafts passing ventral to and beyond sacrum, oblong in cross-section, with a weak dorsal crest, a distinct dorsal prominence, and a shallow oblique groove. Femur weakly sigmoid, bearing a distinct posterior crest. Tibiofibula slightly shorter than femur in length, with a sulcus intermedius. Tibiale and fibulare fused proximally and distally. T1 and T2 +3 tarsals present, T1 considerably smaller than T2+3. Centrale present, larger than other tarsals. Prehallux elongated, half the length of first metatarsal. Phalangeal formula standard (2-2- 3-4-3). Terminal phalanx of toe 1 a small round element, those of toes 2–5 with T-shaped knobs.

Etymology. The species epithet eximia is the feminine form of the Latin adjective eximius meaning ‘remarkable’ or ‘special’, in reference to the surprisingly small body size and terrestrial habits of this Anodonthyla species.

Distribution, natural history, and conservation status. Anodonthyla eximia sp. nov. is known only from Maharira in Ranomafana National Park ( Fig 6 View Fig 6 ). It is a terrestrial species. Nothing else is known of its natural history. It is likely that this species should be classified as Vulnerable like other species from Maharira (e.g. Gephyromantis runewsweeki), but as we know almost nothing of its range and ecology, we instead recommend that it be considered Data Deficient until more data are available.