Description
Sooglossus thomasseti is a small to medium sized frog with a snout-vent length that can reach up to 55 mm in females and 45 mm in males (Nussbaum and Wu 2007). It characteristically has a very depressed head that is wider than it is long. The snout is round and short. The space between the eyes is about the same length as the eyelid. Pupils are horizontal and the tympanum is hidden. The nostril is closer to the most anterior portion of the snout than the eye. It does not have a canthus rostralis, and the loreal region is slightly grooved and oblique. The fingers in general are short with the first finger is shorter than the second. The toes are moderate in length. Neither fingers or toes contain metatarsal tubercles or subarticular. There is no webbing on the digits, the tips of digits have small disks and the terminal phalanges are pointed. The tibio-tarsal articulation meets the eye and the tibia is roughly half the length of the snout-vent length. There is a glandular fold connecting the eye to the shoulder but over all the skin on the body is smooth. Skin is tubercular on hands (Boulenger 1909).

Sooglossus thomasseti is distinct from other Sooglossus species due to the fact it has vomerine teeth and that it does not have claw-like, dermal tips on the digits (Boulenger 1909). It is also significantly larger than the similar Sooglossus sechellensis. Recently, Nussbaum and Wu (2007) have identified fifteen unique derived characters of this species. They are: fleshy discs at the tips of toes and fingers, the muscle of the tensor fascia latae originating on the posterior 1/3 of the ilium, a crest on the posterior half of the frontoparietal, a 45 degree or greater angle between the horizontal process of squamosal and prootic, the squamosal leans posteroventrally, the prevomer dentary processes are posterior to the choana and do not contact medially, presences of prevomerine teeth, the prevomer and palatine fused, a deep hyoglossal sinus of the hyoid, bifurcated posterolateral process of the hyoid, the length of the transverse process III is shorter than IV, the procoracoid is reduced along the lateral edge, and there is a distal expansion of the omosternum.

In life, the dorsal surface of S. thomasseti ranges from reddish-brown to golden. In some individuals there is a broad, brown mid-dorsal stripe. Legs and toes are banded with black bands lines and a thin yellow or white line travels dorsally down the back and along the back of the thighs. Most of the individuals have a white line that extends from behind the eyes backwards to just above the forelimbs. There are two rows of 2 - 6 lightly colored dots running down the back. The eyes are golden with black pupils. The ventral side of the frog is lightly mottled on a brown background (Nussbaum and Wu 2007).

The middorsal strip, the thin white or yellow line down the back and across the thighs, and the white line that runs from the eyes to the forelimbs are all variations (Nussbaum and Wu 2007).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Seychelles

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (2 records).

Sooglossus thomasseti is found on Mahé and Silhouette Islands, of the Seychelles islands in moss forests and in boulder fields. The highest population densities are present in the moss forest area. It can be found to be widespread 400 m above sea level, but peak abundance is at 600 m and higher. One single locality has been noted at 80 m above sea level though. There are greater altitude ranges on Silhouette Island than Mahé Island, where recorded populations are lower. It is thought to be the rarest of the Sooglossus species (Gerlach 2007). It is limited to these localities and elevations because it is intolerant to temperatures over 24 degrees Celsius (Gerlach 2011).

Life History, Abundance, Activity, and Special Behaviors
This rareSooglossus frog is nocturnal and generally arboreal. However, one locality is presumably terrestrial, in the boulder field (Gerlach 2007; Nussbaum and Wu 2007). It is restricted to undisturbed habitats along streams or dried out streambeds and is in the terrestrial or freshwater system (Nussbaum and Gerlach 2004).

Call notes are produced at a slower rate than S. sechellensis, making the call longer. The first gutteral note is repeated more than once, normally 3 - 4 times and the call sounds like, "rraackrraack- rraack-toc-toc-toc-toc” (Nussbaum and Wu 2007).

The exact mode of development and parental care level is unknown. However, it is thought to have direct terrestrial development based on the large yolky eggs, typical of direct developers. Eggs are large and unpigmented. No larvae have been identified as S. thomasseti, but if present would most likely be found in streams or small ponds, as in S. sechellensis and Sechellophryne gardineri. Based on similar species it is also assumed that female egg-guarding is present in this species. (Nussbaum and Wu 2007).

Trends and Threats
In 1996, this species was listed as 'Endangered', but is now listed as 'Vulnerable' by the IUCN because it is only known from two locations with an occupancy area less than 20 km². It is thought to be threatened by habitat degradation, such as fire and invasive species, but is not at a serious risk due to it higher altitude habitat (Nussbaum and Gerlach 2004). This species is also extremely vulnerable to climate change due to its requirement of needing a temperature under 24 degrees Celsius and its very small range. It is experiencing a declining trend due to these factors (Gerlach 2011).

Possible reasons for amphibian decline

General habitat alteration and loss
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
The species authority is Nesomantis thomasseti - Boulenger 1909: 293. Holotype: BM 1907.10.15.111, collected in 1905 by H. P. Thomasset (Nussbaum and Wu 2007).

Sooglossus thomasseti was named after Mr. H. P. Thomasset, who was the collector of the holotype specimen in 1905 (Nussbaum and Wu 2007).

Sooglossus thomasseti was recently placed within Sooglossus, from Nesomantis, thus making it synonymous with Nesomantis thomasseti. It is sister to Sooglosssus sechellensis. That clade is sister to Sechellophryne gardineri. The Sooglossus genus is monophyletic (Nussbaum and Wu 2007).

References

Boulenger GA. 1909. A list of the freshwater fishes, batrachians, and reptiles obtained by Mr. J. Stanley Gardiners expedition to the Indian Ocean. Trans. Linn. Soc. Lond. 12:291-300.

Gerlach J. 2007. Distribution and status of the Seychelles frogs (Amphibia: Anura: Sooglossidae). The Herpetological Journal, 17(2):115-122.

Gerlach, J. 2011. The potential effects of climate change on the status of Seychelles frogs (Anura: Sooglossidae). Journal of Threatened Taxa 3(11):2153–2166.

Nussbaum, R. A., Gerlach, J. (2004.) Sooglossus thomasseti. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. www.iucnredlist.org. Downloaded on 24 June 2013.

Nussbaum, R. A., Wu S.H. 2007. Morphological Assessments and Phylogenetic Relationships of the Seychellean Frogs of the Family Sooglossidae (Amphibia: Anura). Zoological Studies 46(3): 322-335.

Species Account Citation: AmphibiaWeb 2013 Sooglossus thomasseti <https://amphibiaweb.org/species/5213> University of California, Berkeley, CA, USA. Accessed Jan 23, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 23 Jan 2025.

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