Head in the clouds: two new microendemic tepui-summit species of Stefania (Anura: Hemiphractidae)

Abstract

In addition to the type locality (the summit of Aprada-tepui, Bolívar State of Venezuela), the distribution of the egg-brooding frog Stefania satelles was long thought to include several isolated tabletop mountain (tepui) summits surrounding the large Chimantá Massif in Bolívar State (hence the Latin name "satelles"). However, multilocus molecular phylogenetic analyses have revealed that this taxon includes several undescribed morphologically cryptic species, and that S. satelles should be restricted to its type locality. Two tepui-summit species confused under that name in the literature remain to be named, and the present paper aims at describing these populations previously referred to as Stefania sp. 3 and S. sp. 5. Stefania sp. 3 is only known from the small summit of Angasima-tepui, while S. sp. 5 is only reported from the small summit of Upuigma-tepui, both mountains being located south of the Chimantá Massif. These new, phylogenetically distinct species are described based on external morphology and osteology and in comparison to close relatives in the S. ginesi clade, which consists exclusively of tepui summit species. Both new species have highly restricted geographic ranges (less than 3 km²) and should be listed as Critically Endangered according to IUCN criteria.

Keywords: Homoplasy; Morphology; Osteology; Pantepui; Systematics; Taxonomy.

Fig. 1

Distribution of species in the Stefania ginesi clade (A). Distribution map of the Stefania ginesi clade as currently understood. Locality data are based on specimens examined (see Appendix) and literature records [8, 14, 15, 34]. Inset photos by the author. (B). Aerial photograph of the southern part of the Chimantá massif, taken facing southwest showing the distribution of Stefania imawari sp. nov. and S. upuigmae sp. nov. Photo by C. Brewer-Carías

Fig. 2

Type localities and habitats of Stefania imawari sp. nov. and S. upuigmae sp. nov. (A). Angasima-tepui as seen from the summit of Upuigma-tepui; black arrow indicates the exact type-locality of S. imawari. (B–D). Vegetation on the summit of Angasima-tepui. (E). Upuigma-tepui as seen from the summit of Angasima-tepui. (F–H). Vegetation on the summit of Upuigma-tepui. Photos by the author

Fig. 3

Phylogenetic relationships of the Stefania ginesi clade modified from [14], based on 2,359 base pairs of nuclear and mitochondrial DNA (Bayesian statistical supports are provided at nodes, asterisks indicate values > 95%). Stefania sp. 1 and S. sp. 4 remain undescribed and were both confused with S. ginesi. Photos by the author

Fig. 4

Holotype of Stefania imawari sp. nov. (IRSNB 4221, 48.5 mm SVL) (A). Dorsolateral view in life. (B). Ventral view of the specimen freshly euthanized. Photos by the author

Fig. 5

Holotype of Stefania imawari sp. nov. (IRSNB 4221, female, 48.5 mm SVL) after 13 years in ethanol preservative. (A). Dorsal view. (B). Ventral view. Photos by the author

Fig. 6

Palm (A) and sole (B) of the preserved holotype of Stefania imawari sp. nov. (IRSNB 4221, female, 48.5 mm SVL). Photos by the author

Fig. 7

Main colour pattern variation in Stefania imawari sp. nov. (A). IRSNB 4218, male, 48.9 mm SVL. (B). IRSNB 4213, immature female, 38.0 mm SVL. (C). IRSNB 4215, male, 44.1 mm SVL. (D). IRSNB 4214, male, 44.4 mm SVL. (E). IRSNB 4219, male, 44.6 mm SVL. (F). IRSNB 4220, female, 55.4 mm SVL. Photos by the author

Fig. 8

Three-dimensional model of the cranium of the female holotype of Stefania imawari sp. nov. (IRSNB 4221) based on µCT imagery. Top left: dorsal view. Top right: ventral view. Middle: frontal view. Bottom: left lateral view. Abbreviations: ang = angulosplenial, ang.cp = coronoid process of the angulosplenial, col = columella, c.p = cultriform process, d = dentary, exo = exoccipital, fp = frontoparietal, lam.p = lamina perpendicularis, mmk = mentomeckelian, mx = maxilla, mx.pp = posterodorsal projection of the maxilla, na = nasal, na.mp = maxillary process of the nasal, neo = neopalatine, p.f = pars facialis, pmx = premaxilla, pmx.ap = alary process of the premaxilla, pmx.lp = lateral process of the premaxilla, pmx.pp = palatine process of the premaxilla, pro = prootic, psp = parasphenoid, psp.ar = alary process of the parasphenoid, psp.pp = posteromedial process of the parasphenoid, pt = pterygoid, pt.ar = anterior ramus of the pterygoid, pt.mr = medial ramus of the pterygoid, pt.pr = posterior ramus of the pterygoid, qua = quadratojugal, smx = septomaxilla, sph = sphenethmoid, squa = squamosal, squa.or = otic ramus of the squamosal, squa.vr = ventral ramus of the squamosal, squa.zr = zygomatic ramus of the squamosal, v = vomer, v.pcp = postchoanal process of the vomer

Fig. 9

Three-dimensional models of the complete skeletons of one male paratype of Stefania imawari sp. nov. (IRSNB 4214) and the female holotype (IRSNB 4221), and of the female holotype of S. upuigmae sp. nov. (IRSNB 4222) based on µCT imagery, in dorsal, ventral and left lateral views

Fig. 10

Male nuptial excrescences (thumb) in (A). Stefania imawari sp. nov. (IRSNB 4219) and (B). S. lathropae (IRSNB 4212). Photos by the author

Fig. 11

Holotype of Stefania upuigmae sp. nov. (IRSNB 4222, female, 53.1 mm SVL). (A). Dorsolateral view in life. (B). Ventral view of the specimen freshly euthanized. Photos by the author

Fig. 12

Holotype of Stefania upuigmae sp. nov. (IRSNB 4222, female, 53.1 mm SVL) after 12 years in ethanol preservative (A). Dorsal view. (B). Ventral view. Photos by the author

Fig. 13

Palm (A) and sole (B) of the preserved holotype of Stefania upuigmae sp. nov. (IRSNB 4222, female, 53.1 mm SVL). The thin red line highlights a row of distinctly enlarged supernumerary plantar tubercles (absent in S. imawari sp. nov.; compare with Fig. 6). The red arrow highlights the distinctly enlarged outer metatarsal tubercle (not enlarged in S. imawari sp. nov.; compare with Fig. 6). Photos by the author

Fig. 14

Three-dimensional model of the cranium of the female holotype of Stefania upuigmae sp. nov. (IRSNB 4222) based on µCT imagery. Top left: dorsal view. Top right: ventral view. Middle: frontal view. Bottom: left lateral view. Abbreviations: ang = angulosplenial, ang.cp = coronoid process of the angulosplenial, col = columella, c.p = cultriform process, d = dentary, exo = exoccipital, fp = frontoparietal, lam.p = lamina perpendicularis, mmk = mentomeckelian, mx = maxilla, mx.pp = posterodorsal projection of the maxilla, na = nasal, na.mp = maxillary process of the nasal, neo = neopalatine, p.f = pars facialis, pmx = premaxilla, pmx.ap = alary process of the premaxilla, pmx.lp = lateral process of the premaxilla, pmx.pp = palatine process of the premaxilla, pro = prootic, psp = parasphenoid, psp.ar = alary process of the parasphenoid, psp.pp = posteromedial process of the parasphenoid, pt = pterygoid, pt.ar = anterior ramus of the pterygoid, pt.mr = medial ramus of the pterygoid, pt.pr = posterior ramus of the pterygoid, qua = quadratojugal, smx = septomaxilla, sph = sphenethmoid, squa = squamosal, squa.or = otic ramus of the squamosal, squa.vr = ventral ramus of the squamosal, squa.zr = zygomatic ramus of the squamosal, v = vomer, v.pcp = postchoanal process of the vomer

Fig. 15

Three-dimensional models of the complete skeletons of the male holotype (IRSNB 4208) and one female paratype of Stefania lathropae (IRSNB 4210) based on µCT imagery, in dorsal, ventral and left lateral views