Federal Republic of Nigeria, coll. R.B.N. Walter. To stabilize the identity of the nomen, we designate BMNH 1947.2.24.83 (a late stage metamorph) as the lectotype. Diagnosis.–Xenopus tropicalis exhibits all of the morphological features of subgenus Silurana described above, and is diagnosable from other species in the subgenus by unique nucleotide substitutions in mitochondrial and autosomal DNA (mitochondrial DNA is paraphyletic; Figs 1 and 2 and S1 and S2), by having a trill-type call, and by being the only GSK-AHAB custom synthesis diploid in the genus. In addition, it differs from other species of Silurana by having higher intensity modulation ( 38) of its call in contrast to other species (which is 10), Table 4, [42]. As noted above, characters previously proposed as diagnostic between X. epitropicalis and X. tropicalis, including adult body size, number of lateral-line plaques around the eye, and coloration (Fischberg et al., 1982; Kobel et al., 1996), are not useful for distinguishing these two species. Comments on syntypes.–The four syntypes are two late-stage tadpoles and two metamorphs in stages corresponding to NF 57?0 based on the staging developed by Nieuwkoop and Faber [73] for X. laevis (S9 14 Figs). Two specimens, BMNH 1947.2.24.84 and 86 are incomplete due to damage of the posteriormost tail (respectively, NF 59 at 46 mm total length, and NF 58 at 37 mm total length). The latest stage individual (BMNH 1947.2.24.83) is at NF 59/60 with aPLOS ONE | DOI:10.1371/journal.pone.0142823 December 16,28 /Six New Species of African Clawed Frog (Xenopus)total length of 54 mm, whereas the earliest stage specimen (BMNH 1947.2.24.85) has a total length of 63 mm. As indicated in the original description, these larval specimens have elongate barbels as is typical of species in the subgenus Silurana. The coloration of the latest stage individual (BMNH 1947.2.24.83) is GW856553X web medium brown with scattered darker brown variegations (S9?S14 Figs), with a venter that is pale creamy beige and a small stark white region at the opercular region. The specimen lacks pigmentation on the pedal webbing and has three dark keratinous pedal claws as well as wcs.1183 a similar claw on the prehallux. The other specimens are largely consistent in appearance, and all appear to have faded in coloration over time. We designate the latest stage individual BMNH 1947.2.24.83 as the lectotype. Variation.–Variation in the lateral-line based on specimens from across the geographic range of this species in West Africa (n = 15, given as mean and range): orbital?10 (8?2); oral?11 (9?2); medial?18 (16?1); lateral?20 (17?2); ventral?18 (16?1). Vocalization.–Xenopus tropicalis has a trill-type call with higher intensity modulation than in other species [42]. Karyotype.–Xenopus tropicalis is the only diploid species of Xenopus with a karyotype of 2n = 20 [51, 60]. Habitat and range.–Based on samples with available genetic data, X. tropicalis is widespread across West Africa, extending from Sierra Leone east to at least into western Cameroon [1, 59]. We lack genetic data for samples from central Cameroon, though previously Tinsley et al. [1] recognized the easternmost extent of this species as the Sanaga River.Subgenus Xenopus Wagler, 1827 [44]Previous authors divided Xenopus into subgroups including the j.neuron.2016.04.018 laevis subgroup (X. laevis sensu lato, X. gilli, X. largeni), the muelleri subgroup (X. muelleri, X. borealis, X. clivii and an undescribed species X. “new tetraploid” / X. “muelleri west” that is described.Federal Republic of Nigeria, coll. R.B.N. Walter. To stabilize the identity of the nomen, we designate BMNH 1947.2.24.83 (a late stage metamorph) as the lectotype. Diagnosis.–Xenopus tropicalis exhibits all of the morphological features of subgenus Silurana described above, and is diagnosable from other species in the subgenus by unique nucleotide substitutions in mitochondrial and autosomal DNA (mitochondrial DNA is paraphyletic; Figs 1 and 2 and S1 and S2), by having a trill-type call, and by being the only diploid in the genus. In addition, it differs from other species of Silurana by having higher intensity modulation ( 38) of its call in contrast to other species (which is 10), Table 4, [42]. As noted above, characters previously proposed as diagnostic between X. epitropicalis and X. tropicalis, including adult body size, number of lateral-line plaques around the eye, and coloration (Fischberg et al., 1982; Kobel et al., 1996), are not useful for distinguishing these two species. Comments on syntypes.–The four syntypes are two late-stage tadpoles and two metamorphs in stages corresponding to NF 57?0 based on the staging developed by Nieuwkoop and Faber [73] for X. laevis (S9 14 Figs). Two specimens, BMNH 1947.2.24.84 and 86 are incomplete due to damage of the posteriormost tail (respectively, NF 59 at 46 mm total length, and NF 58 at 37 mm total length). The latest stage individual (BMNH 1947.2.24.83) is at NF 59/60 with aPLOS ONE | DOI:10.1371/journal.pone.0142823 December 16,28 /Six New Species of African Clawed Frog (Xenopus)total length of 54 mm, whereas the earliest stage specimen (BMNH 1947.2.24.85) has a total length of 63 mm. As indicated in the original description, these larval specimens have elongate barbels as is typical of species in the subgenus Silurana. The coloration of the latest stage individual (BMNH 1947.2.24.83) is medium brown with scattered darker brown variegations (S9?S14 Figs), with a venter that is pale creamy beige and a small stark white region at the opercular region. The specimen lacks pigmentation on the pedal webbing and has three dark keratinous pedal claws as well as wcs.1183 a similar claw on the prehallux. The other specimens are largely consistent in appearance, and all appear to have faded in coloration over time. We designate the latest stage individual BMNH 1947.2.24.83 as the lectotype. Variation.–Variation in the lateral-line based on specimens from across the geographic range of this species in West Africa (n = 15, given as mean and range): orbital?10 (8?2); oral?11 (9?2); medial?18 (16?1); lateral?20 (17?2); ventral?18 (16?1). Vocalization.–Xenopus tropicalis has a trill-type call with higher intensity modulation than in other species [42]. Karyotype.–Xenopus tropicalis is the only diploid species of Xenopus with a karyotype of 2n = 20 [51, 60]. Habitat and range.–Based on samples with available genetic data, X. tropicalis is widespread across West Africa, extending from Sierra Leone east to at least into western Cameroon [1, 59]. We lack genetic data for samples from central Cameroon, though previously Tinsley et al. [1] recognized the easternmost extent of this species as the Sanaga River.Subgenus Xenopus Wagler, 1827 [44]Previous authors divided Xenopus into subgroups including the j.neuron.2016.04.018 laevis subgroup (X. laevis sensu lato, X. gilli, X. largeni), the muelleri subgroup (X. muelleri, X. borealis, X. clivii and an undescribed species X. “new tetraploid” / X. “muelleri west” that is described.
