Arthroleptis langeri Rödel, Doumbia, Johnson & Hillers 2009

The holotype, a subadult male, measures 16.2 mm SVL. This species can be distinguished from congeners by the combination of color pattern, completely smooth skin (except for the vertebral raphe), rounded canthal region, and more slender body shape (Rödel et al. 2009).Smooth dorsal and ventral skin. The back has a fine vertebral skin raphe. Body shape is oval, slender and slightly elongated. Large eyes. Short snout which is rounded in dorsal view and almost spatulate in lateral view. Indistinct and rounded canthus rostralis with a slightly concave loreal region. Tympanum is small and indistinct. Males can be distinguished from females by a slightly longer third finger. No digital or inguinal spines are present. Fingers and toes lack webbing. The tips of both the fingers and toes are slightly expanded, but they do not form discs. Fingers have small round or ovoid subarticular tubercles. Hand has large and ovoid palmar and thenar tubercles. Foot lacks a tarsal tubercle, but have a slender and elongated internal metatarsal tubercle (no outer metatarsal tubercle was visible, but the specimen's feet were reported to be slightly dried) (Rodel et al. 2009).In life, the dorsum is reddish brown, with a black interorbital marking on the head, posterior to which is a small black U-shape surrounding a gray spot, then two black comma-shaped marks, then followed by a black-bordered crown-shaped marking just below the scapular region, and a small black marking in the middle of the dorsum. Snout and upper eyelids are gray with black and brown mottling. Blackish loreal region. Mandible is blackish. Upper arms are reddish brown, with a darker base at the arm insertion, while the lower arms are nearly black except for lighter blotches on the elbow and near the hand. The ventral surfaces of the upper arms are dark brown. Hands and feet are gray. Upper legs are reddish brown with a single dark transverse bar and several irregular blackish spots; lower legs also have a single dark transverse bar but a reddish spot on the most distal third of the leg. The ventral surfaces of the upper legs are whitish and the ventral surfaces of the lower legs are dark brown. Flanks are blackish, with a dark pattern interrupted by a reddish brown stripe that runs from behind the scapular crown marking to the groin. Anterior to the groin area, there are more dark markings and inguinal bands. Throat is dark brown. Belly is gray. Reddish iris. (Rödel et al. 2009).In preservative, the color appears a faded grayish brown, but the pattern is still distinguishable (Rödel et al. 2009).The species is named after Detlev Langer, who worked as a technical assistant in the herpetological section of the Museum für Naturkunde, Berlin (Rödel et al. 2009).The report of yet another new amphibian species from Mount Nimba, one of the most intensively herpetologically surveyed areas in West Africa, underscores how much work still remains to fully assess West African amphibian taxa. Mount Nimba has the highest diversity of amphibians known (67 species) in West Africa (Rödel et al. 2009).

The type location is at the south-eastern tip of the Mount Nimba range, Liberia at 567 m ASL. This species is expected to be found in nearby forests in Liberia as well as forests in Guinea and Côte d’Ivoire. The holotype was collected in primary forest with an almost completely closed canopy. At the time of the collection it was dry season, and the specimen was found within a nearly dry river bed. A minimal amount of water was flowing over rocks and creating small puddles (Rödel et al. 2009).

The holotype was active when it was found, shortly after mid-day. Stomach contents included three to four specimens of different tiny ant or termite species (determined by the different shape of mandibles and thoracic parts present) (Rödel et al. 2009).

Only a single specimen is known, so it is not possible to assess population trends. This species is currently considered Data Deficient.