Limnonectes sinuatodorsalis Matsui 2015

Limnonectes sinuatodorsalis is a small frog with males having a snout-vent length of 28 - 32 mm while females measure 34 – 38 mm. Their heads are not enlarged and are longer than they are wide. The snout is slightly pointed, truncate from the profile, and projects beyond the lower jaw. Their eye length is slightly larger than the snout. The skin on the eyelids is very weakly wrinkled and the skin on the top of the snout is smooth. The transverse fold between the posterior margins of the eyes are very weak. They have a rounded canthus and a slightly sloping, concave lore. The nostril is dorsolateral is slightly closer to the snout than the eye. The internarial distance is wider than the interorbital distance, with the interorbital being slightly wider than the upper eyelid. The pineal spot is not visible and the tympanum, while indistinct, is visible and oval. The tympanum’s diameter is more than half the length of the eye and is separated from the eye by half the diameter of the tympanum (Matsui 2015). The forelimbs are thick and short with moderately slender fingers and relative finger lengths of II < I < I V < III. The length of the first finger, which is measured from the distal edge of the inner palmar tubercle, is shorter than the length of the eye. The tips of the fingers are slightly swollen, forming small pads without circummarginal grooves. The pads are not distinctly wider than basal phalanges. There are remnants of webs between fingers. The inner palmar tubercle is moderate, oval, and slightly elevated. The middle palmar tubercle is oval and smaller than the inner palmar tubercle and does not touch the inner palmar tubercle. The outer palmar tubercle is elongated, as large as the middle tubercle. The proximal subarticular tubercles are oval and elevated. The distal subarticular tubercle is low but distinct. There are no supernumerary metacarpal tubercles. There are narrow ridges of skin on edges of the third finger that do not move freely. Nuptial pads cover the surface of the first finger from the base to the subarticular tubercle (Matsui 2015).The hindlimbs are thick, short, and less than three times the length of the forelimb. The tibia is short and the heels do not overlap when limbs are held at right angles to the body. When the tibiotarsal is pressed against the body, the limbs reach to the posterior corner of the eye. Small, low warts are scattered on the dorsal surface of the tibia and the tarsus. On the tarsus there is a thick dermal ridge extending proximally from the metatarsal tubercle. The foot is slightly longer than the tibia with relative toe lengths of I < II < V < III < IV. The tips of the toes are swollen into small disks with the webbing formula: I 0 – 1 II 0 – 1 III 0 – 2 IV 2 – 1 V. There is a flap of skin along the outer edge of the fifth toe that can be moved freely. The subarticular tubercles are oval and distinct. There is an elongated inner metatarsal that is more than half the length of the first toe. There is no outer metatarsal tubercle. The dorsal skin has few warts and is extremely folded with networks of wrinkles running in all directions. The temporal fold extends from the eye to above the insertion of the upper arm. There are fine warts around the anus. The side of the trunk is reticulated with fine wrinkles. Longitudinal wrinkles cover the throat while the chest and abdomen are smooth. There is no modification to the skin of the gular region (Matsui 2015). Limnonectes sinuatodorsalis is similar to L. cintalubang, L. hikidai, and L. rhacodus, however, L. sinuatodorslis has a smaller male snout-vent lenght and a dorsal skin network of heavy wrinkles and fewer tubercles. The tympanum is also visible but not distinct in L. sinuatodoslis and the dorsum is a reddish brown without light markings. More specifically, when compared to L. cintalubang, the focal species has rougher skin and a heavier network of wrinkles. Limnonectes rhacodus has a similar amount of wrinkles as L. sinuatodorsalis but run across the dorsolateral fold while wrinkles run in all directions on L. sinuatodorsalis. While similar in appearance to L. asperatus, L. sinuatodoslis has fewer tubercles. Limnonectes sinuatodorsalis has more developed webbing on its fourth toe than L. hikidai. And lastly, the flaps along both edges of the third fingers are not movable in L. sinuatodorslis, unlike Limnonectes cf. kuhlii (Matsui 2015).In preservative, L. sinuatodorslis have a reddish brown dorsum without darker markings except for dark brown markings on its interorbital upper eyelid and on the top of its snout. There is also an oblique dark drown temporal stripe on and along the supratympanic fold from behind the eye to above the arm insertion. The side of the head, from posterior half of the lore to the inguinal area, is a paler brown. The lateral side of the trunk has dense brown spots that were formed by reticulation of the lighter colored wrinkles. There are dark brown bars on the upper lip and brown with white spots on the lower lip. Dorsally, the limbs don’t have dark crossbars. The throat is dark brown with cream spots, the chest and abdomen are also cream. The ventral side of the limbs are spotted brown, with heavier spots on the posterior thigh. The ventral surface of the hand is dark brown. Nuptial pads appear on the medial surface of the first finger as a distinct yellow-brownish tinge without asperities (Matsui 2015).Adult males are smaller than the females in snout-vent length. Some of the other dimensions appear to be sexually dimorphic, with males having larger forelimbs, tibia, foot, hind limb, thigh, and inner metatarsal relative to snout-vent length (Matsui 2015).The species authority is: Matsui, M. (2015). ''A new species of Limnoncetes from the boarder of East Kalimantan and Sarawak, Borneo Island (Anura, Dicroglossidae).'' Current Herpetology, 34(2), 120-127.Only a morphological examination was done but it is believed that even without molecular or acoustic information the focal species is significantly different from other species. It is strongly suggested that L. sinuatodoslis would be in the same clade as L.asperatus, L. cintalubang, and L. hikidai. It is also likely that L. sinuatodoslis is phylogenetically related to L. hikidia and it is possible that they could co-inhabit. However, female L. sinuatodoslis were gravid with a smaller number but larger in size ova than L. asperatus and L. hikidia, indicating that there are distinct breeding habits between the species (Matsui 2015).The species epithet, “sinuatodorsalis” is latin for folded back and refers to the folds on the dorsum of this frog (Matsui 2015). Limnonectes sinuatodorsalis is synonymous with L. hikidai (Matsui 2015). The specimens used to describe the species were found in 1981 and 1991 but were not described until 2015 because they were believed to be L. hikidai (Matsui 2015). Fanged frogs are not easily identifiable, and it is predicted that more will be found in these area upon a closer inspection (Matsui 2015).

The only known range of L. sinuatodorslis is from the central mountains of Long Api, Krayan of East Kalimantan, Indonesia, and from Bario, Kelabit Highlands of Sarawak, East Malaysia (Matsui 2015).

Female L. sinuatodorslis that were collected from these areas between July and January were gravid with a small number of large ova. These characteristics contrast the breeding of L. kuhlii (larger number of smaller eggs), which live in the same habitat, and indicates distinct breeding habits between the two species. The L. sinuatodorsliseggs found were pigmented, meaning that they would not be spawned completely in the dark locations (Matsui 2015).The specimens were found along small streams in partly logged rain forests with Limnonects cf. kuhlii in Long Api and Bario. In Long Api they were also found with Anonis sp. and Megophrys nasuta. Leptobrachium kantonishikawai were also found with L. sinuatodoslis in Bario (Matsui 2015).

Limnonectes sinuatodorsalis is a species of fanged frog in the family Dicroglossidae. It is endemic to Borneo, where it was found in the border region of East Kalimantan and Sarawak.