Description
Odontobatrachus natator is a robust frog, and its head is longer than it is wide. The snout is short and round in both lateral and dorsal views. The snout-vent length ranges from 42.6 - 52.5 mm in adult males, averaging 48.0 mm, and ranges from 44.6 - 61.1 mm in adult females, averaging 53.6 mm. There are large, tusk-like teeth on the lower jaw, and both the upper premaxillae and maxillae have a large number of teeth. The tongue is shaped somewhat like a broad heart. The canthus rostralis is round, and the loreal region is concave. The eye is larger in diameter than the tympanum, and as long as the snout diameter. The pupil is horizontally elliptical, and the tympanum is inconspicuous (Barej et al. 2015 Zoosyst).

The forearms of O. natator are somewhat slender, but also muscular and hypertrophied. The fingers are also slender, and the relative finger lengths are III > IV > II > I. The subarticular tubercles are distinct and subconical in shape. There are no supernumerary tubercles. The fingertips are triangular and enlarged (Barej et al. 2015 Zoosyst).

The hind limbs are also slender and muscular, and have small round glands running across the upper side of the tibia. The inner metatarsal tubercle is elliptical and distinct. The toes have relative lengths IV > III > V > II > I. The toe tips, like the fingertips, are triangular and enlarged. There are subconical subarticular tubercles on the toes, and they are distributed as such: 1, 1, 2, 3, 2, respectively on toes I - V respectively. There are no supernumerary tubercles. The webbing is fully developed, and is nearly straight, barely concave. The webbing formula is 0 - 0.5/0 - 1/0 - 1/1 - 0 (Barej et al. 2015 Zoosyst).

There are prominent folds on the feet posteriorly. The dorsal skin is varied, and there are slender dorsal ridges present on the dorsum and the flanks. The venter is smooth (Barej et al. 2015 Zoosyst).

Odontobatrachus natator is assigned to the Odontobatrachus genus due to its tusk-like teeth on the lower mandible, distinct vomerine teeth, and curved teeth on both the premaxillaries and the anterior maxillaries. When compared to its congeners, O. natator is smaller than O. arndti and O. smithi, and larger than O. fouta and O. ziama. Odontobatrachus natator has a less extensive webbing than O. ziama, and more extensive webbing than in O. arndti, O. fouta, and O. smithi. The femoral glands of O. natator are rose-coloured, but are bright orange in O. fouta, pale orange in O. smithi, and dark orange in O. ziama (Barej et al. 2015 Zoosyst).

Coloration:
In life, O. natator has a greenish-brown dorsal color, with dark mottling all over consisting of dark spots. The ventral color varies from pale to dark, but is not mottled, unlike the dorsum. The femoral glands are usually rose-colored (Barej et al. 2015 Zoosyst).

In preservative, adult O. natator are generally brownish but can also be greenish and light brownish. The dorsum is darker than the venter, and the throat is darker than the belly. The venter lacks marbling and patterns (Barej et al. 2015 Zoosyst).

There appears to be sexual dimorphism in O. natator, as females are distinctly larger than males, having an average snout-vent length of 53.6 mm, as opposed to the male's average snout-vent length of 48.0 mm. Females also have longer limbs, fingers, and toes, broader heads, and more elongated snouts. However, the proportions of females are very similar to those of males, and the coloration of O. natator does not seem to be sex-dependant. The webbing formula varies among O. natator individuals. The number of dorsal ridges also varies in the species, ranging from two to six ridges. Coloration in life varies from uniformly brownish, to greenish or light brownish background color with mottling of dark spots. Ventral coloration ranges from very pale, to entirely dark, and everything in between (Barej et al. 2015 Zoosyst).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Cote d'Ivoire, Guinea, Sierra Leone

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (12 records).

Odontobatrachus natator is known from Sierra Leone, Liberia, and Guinea at elevations that range from 250 m to 1400 m. This species extends to the Fouta Djallon region of Guinea. There are two molecular clades of O. natator, one of which is restricted only to the Freetown Peninsula of coastal Sierra Leone, and the other which covers the rest of the O. natator range. The range of O. natator overlaps with that of O. arndti and O. ziama in east Guinea (Barej et al. 2015 Zoosyst).

Life History, Abundance, Activity, and Special Behaviors
Individuals of O. natator were found in a mountain torrent with a rocky bed. Full-grown individuals attach themselves to rocks and roots of trees by means of their digital discs (Boulenger 1905).

Larva
A tadpole description is given by Doumbia et al. (2018) from 13 tadpoles in Gosner stages 25 - 43. The average length was 36.19 mm, and ranged from 18.3 - 49 mm. The body length averaged 10.75 mm, and ranged from 5 - 15.1 mm. The tail length averaged 25.27 mm, ranging from 12.5 - 35.1 mm. The body of larval O. natator is dorsoventrally flattened and broad, and of a nearly rectangular shape. The snout is also broad and rounded. The nostrils are pointed dorsally and directed anterolaterally, and are closer to the eyes, than to the snout. The eyes are small, and are both positioned, and directed dorsolaterally. There is a large sucker-like oral disc, which allows the tadpole to attach to nearby rocks. The keratodont formula is 4/5. The upper jaw is smooth, and has an M shape, while the lower jaw is rough and serrated, and has a V shape. The spiracle of larval O. natator is median, and positioned sinistrally, directed posterodorsally. It is distinct lateral and ventral. The tail, which makes up on average 70% of its entire length, has narrow fins that are moderately pronounced. The dorsal fin originates slightly posterior to the base of the tail, and the ventral fin originates at the end of the body. Both fins are narrower than the tail axis (Doumbia et al. 2018).

Odontobatrachus natator larva only has minute morphological differences from other larvae in the genus. Odontobatrachus natator are one of the smaller tadpoles and the only tadpoles to exhibit white tail tips. Additionally, O. natator, as well as O. smithi, has tail fins of equal height, while the dorsal fin is taller in O. arndti, O. fouta, and O. ziama. The margin of the dorsal tail fin in O. arndti is curved, whereas it is straight in O. natator as well as in O. fouta, O. smithi and O. ziama. There are also small differences in the length of the anterior keratodont rows, from the tip of the snout to the mouth opening, with O. nator having the same lengths as O. fouta and O. smith of 3 > 2 = 4 > 1 verses 4 = 3 > 2 > 1 in O. arndti, and 3 = 2 > 1 > 4 in O. ziama. Furthermore, the round tubercle-like marginal papillae in O. natator, O. fouta, and O. smithi is in contrast with the short, round marginal papillae in O. arndti and the blunt-triangular marginal papillae in O. ziama. However, these differences should only be used for diagnosis in combination with locality and genetic information (Doumbia et al. 2018).

Coloration in life, larval O. natator are light to dark brown, both dorsally and laterally. There is sometimes mottling of dark brown, light yellow, or even reddish spots. The oral disc region and also spiral guts are silvery-grey or white. The ventral region is a pink flesh-toned. The tail fins are translucent and grey, and the tail tips are either black, or more commonly, white (Doumbia et al. 2018).

In preservative, the overall dorsal coloration of larval O.natator fades to light beige. The dorsal surfaces, including the tail, retain their darker brown mottled patterning. There are also dark brown patches that are especially pronounce in the loreal region. The tail has a medial, dark brown strip. The tail fins are slate black but often have a white tip. The background color of the flanks and venter is whitish. On the ventral surface, there is a dark line from the tip of the snout to the vent (Doumbia et al. 2018).

Trends and Threats
Odontobatrachus natator is threatened by habitat loss and increased agricultural development, as well as logging and urbanization. Odontobatrachus natator is also threatened by mining activities in some areas, such as the Shimandou Range, and also on Mount Nimba. Despite these ever-increasing threats, O. natator is considered "Least Concern" due to its widespread distribution and large population (IUCN 2019). However, upon close investigation, Barej et al. (2015 BMC) discovered an inconsistency in the IUCN status classification of O. natator. In their study of the distribution of O. natator, Barej et al. found that there were actually two lineages in this species, one that is isolated to the Freetown Peninsula, and the other that encompasses the rest of the species. As one would expect, they found that both the Area of Occupancy, and the Extent of Occurrence for both lineages were significantly lower than the combined values of the entire species. The Area of Occupancy of the two lineages of O. natator together was 180.231 km², and the Extent of Occurrence was 224 km². These values do indeed warrant the "Least Concern" IUCN status. However, the Area of Occupancy of the Freetown Peninsula lineage was 34 km², and its Extent of Occurrence was 20 km², which warrants this lineage the status of "Critically Endangered." Likewise, the Area of Occupancy of the rest of the species was 132.175 km², and the Extent of Occurrence was 204 km², which warrants this larger lineage the status of "Endangered" (Barej et al. 2015 BMC).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Urbanization
Mining

Comments
Etymology:
The genus Odontobatrachus is a combination of two Greek words: "Odous," which means "tooth," and "batrachos," which means "frog." This name is a reference to the long maxillary teeth and lower jaw tusks of O. natator and its, at the time, undescribed congener (Barej et al. 2014).

The specific epithet "natator" means "swimmer", thus named for its webbed feet. It is also known as a torrent frog, inhabiting rapid-flowing streams (Boulenger 1905).

Phylogenetics:
Odontobatrachus natator was initially placed into the Petropedetes genus, but a reevaluation of phylogeny found that there were 88 unique character states that differentiated O. natator from the Petropedetes genus (and 93 from the Arthroleptis genus). Two phylogenetic analyses were performed by Barej et al. (2013): one Bayesian Inference, and one Maximum Likelihood test. Based on these two phylogenetic analyses, which examined the 16S, 12S, cyt b, mitochondrial and BDNF, SIA, and rag1 nuclear genes, the Odontobatrachus genus was found to be sister to a clade formed by the Arthroleptis, Cacosternum, Conraua, Petropedetes, and Phrynobatrachus genera (Barej et al. 2013).

After the distinction of O. natator from the Petropedetes genus in 2013, there were initially only two species in the Odontobatrachus genus: Odontobatrachus natator, and an undescribed second species (Barej et al. 2015 Zoosyst). However, in 2015, Barej et al. found that the Odontobatrachus genus was actually composed of 5 distinct species: Odontobatrachus arndti, O. fouta, O. natator, O. smithi, and O. ziama. Phylogenetic analysis of the 16S, 12S, cyt b mitochondrial genes, and BDNF, SIA, and Rag1 nuclear genes, it was found that O. natator was sister to a clade formed by O. arndti and O. ziama. The clade formed by these three species is sister to a clade formed by O. fouta and O. smithi (Barej et al. 2015 BMC).

This species was featured in News of the Week May 30, 2022:

In most frogs, adults are considered to be primarily carnivorous with only a few species known to consume non-animal matter regularly. Schäfer et al. (2022) thoroughly investigated plant ingestion in all five species of the West African frog genus Odontobatrachus and two similar sized, sympatric species. The authors convincingly demonstrate that Odontobatrachus species are deliberately eating the leaves of the riparian tree Parkia bicolor through a combination of stomach-flushing hundreds of frogs across populations and seasons, a detailed capture-mark-recapture study, and a feeding experiment. Despite consuming large quantities of this particular leaflet, however, it does not appear that the frogs digest this plant material, and thus it is unclear why they are eating it. Overall, this study provides important insights into the diets of a unique frog radiation and highlights exciting areas for future research to better understand plant ingestion in this unusual group. (Written by Rayna Bell)

References

Barej, M. F., Penner, J., Schmitz, A., Rödel, M.-O. (2015). ''Multiple genetic lineages challenge the monospecific status of the West African endemic frog-family Odontobatrachidae.'' BMC Evolutionary Biology, 15(67).

Barej, M. F., Rödel, M.-O., Loader, S. P., Menegon, M., Gonwouo, N. L., Penner, J., Gvozdik, V., Gunther, R., Bell, R. C., Nagel, P. Schmitz, A. (2013). ''Light shines through the spindrift - phylogeny of African torrent frogs (Amphibia, Anura, Petropedetidae). .'' Molecular Phylogenetics and Evolution, 71, 261-273.

Barej, M. F., Schmitz, A., Günther, R., Loader, S. P., Mahlow, K., Rödel, M-O. (2014). ''The first endemic West African vertebrate family - a new anuran family highlighting the uniqueness of the Upper Guinean biodiversity hotspot.'' Frontiers in Zoology, 11(8).

Barej, M. F., Schmitz, A., Penner, J., Doumbia, J., Sandberger-Loua, L., Hirschfeld, M., Brede, C., Emmrich, M., Kouamé, N. G. G., Hillers, A., Gonwouo, N. L., Nopper, J., Adeba, P. J., Bangoura, M. A., Gage, C., Anderson, G. and Rödel, M.-O. (2015). ''Life in the spray zone – overlooked diversity in West African torrent-frogs (Anura, Odontobatrachidae, Odontobatrachus).'' Zoosystematics and Evolution, 91(115-149).

Boulenger, G. A. (1905). ''Descriptions of new West-African frogs of the genera Petropedetes and Bulua.'' Annals and Magazine of Natural History, Series 7, 15, 281-283.

Doumbia, J., Sandberger-Loua, L., Schulze, A., Rodel, M-O. (2018). ''The tadpoles of all five species of the West African frog family Odontobatrachidae (Amphibia, Anura).'' Alytes, 36 (1-4), 63-92.

IUCN SSC Amphibian Specialist Group. 2019. Odontobatrachus natator. The IUCN Red List of Threatened Species 2019: e.T89114149A16927936. Downloaded on 29 January 2021.

Species Account Citation: AmphibiaWeb 2022 Odontobatrachus natator: Saber-toothed Frog <https://amphibiaweb.org/species/3742> University of California, Berkeley, CA, USA. Accessed Oct 5, 2022.

Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Oct 2022.

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