Limnonectes timorensis (Smith, 1927)

Kaiser, Hinrich, Carvalho, Venancio Lopes, Ceballos, Jester, Freed, Paul, Heacox, Scott, Lester, Barbara, Richards, Stephen J., Trainor, Colin R., Sanchez, Caitlin & O'Shea, Mark, 2011, The herpetofauna of Timor-Leste: a first report, ZooKeys 109, pp. 19-86 : 29-31

Limnonectes timorensis (Smith, 1927) Fig. 5

Common names.

(E) Timor River Frog. *(T) Manduku mota (manduku = frog, mota = river).

Identification.

Frogs of the genus Limnonectes are nocturnal and generally quite difficult to distinguish from similar species. Limnonectes timorensis is currently the only known species of river frog recorded from Timor-Leste. Identifying characteristics include fingertips that are slightly swollen and widened at their tips, but which do not possess a marginal fold that outlines the disk pad. The first finger is invariably longer than the second. They possess a dorsolateral fold that originates just behind the eye and continues dorsally to the groin, and a tympanum that is nearly equal to the size of the eye ( Fig. 5 ). A brown band is present on the head, arising near the tip of the snout, continuing along the canthus rostralis through the eye, and completely enveloping the tympanum. The skin warts commonly found concentrated on the dorsum in other species of Limnonectes are reduced in number on the dorsum but quite prominent on the side of the body ( Fig. 5 ). We were readily able to confirm our identification by consulting the figure presented in Smith (1927: Pl. II, Fig. 1) and from the original description.

Variation.

Whereas in one of our specimens the internarial distance is slightly greater than the interorbital distance, a diagnostic characteristic provided by Smith (1927), the internarial distance is equal to the interorbital distance in the second. Even though Smith (1927) did outline some variation among his eight specimens, only slight differences in the interorbital distance are mentioned. It appears that the comparison of internarial distance with interorbital distance by itself is insufficient to distinguish this species from others.

In a second instance of incongruity between our specimens and the original description, the nares are not at the midway point between the eye and the tip of the snout but located approximately one third of the eye-to-snout distance away from the snout in both specimens. We believe that this incongruity could be due to an error in Smith’s (1927) description since the drawing of the frog ( Smith 1927: Plate II, Figure 1) conforms to our specimens and not to Smith’s description. Scientific illustrators are generally extremely meticulous and accurate, and misplacement of the nares, a key character of the head, would be an unlikely error.

Lastly, the foot in our specimens is 7% longer than, as opposed to equal to, tibia length as described by Smith (1927). Repeated measurements with digital calipers and mechanical calipers as used in Smith’s day resulted in measurement errors of 3% and 7%, respectively (n = 10 for each instrument). We therefore believe that the discrepancy between foot and tibia length measurements we made on our specimens, and Smith made on his, is due to slight variation in the hindlimbs ( Smith 1927:212), combined with measurement error, and does not represent a diagnostic difference.

Collection and natural history.

Two female individuals were collected during a single night from the Meleotegi River, near Eraulo, Ermera District, altitude 1179 m. During the dry season, the Meleotegi River is a relatively shallow stream that runs over pebbles and allows easy crossing. Boulders are distributed at irregular intervals along and in the riverbed. It is clear from the steeply eroded riverbanks (over 5 m high in some parts) that the river carries a large volume of water during parts of the year. One individual of Limnonectes timorensis was collected from a thin branch overhanging the relatively steep riverbank, whereas the other was found on a large boulder in midstream. No vocalizations were heard.

Taxonomic comment.

Forcart (1953) and Menzies (1987) considered Limnonectes timorensis a synonym of Hylarana elberti Roux 1911. F orcart’s (1953) synonymy was based on a comparison of specimens in the Naturhistorisches Museum Basel, Switzerland with the holotype of Hylarana elberti by Robert Mertens. One of us (HK) has made a very careful comparison of our Limnonectes timorensis specimens with the holotype of Hylarana elberti , and found differences in the tuberculation of the hand, the width of fingertips, the position and size of the rictal gland at the angle of the jaw, the extent of toe webbing, the width of the toe tips, and the patterning and consistency of the skin on the throat. Additional features of the shape of the head are difficult to compare because the holotype of Hylarana elberti has a damaged anterior of the head. We therefore agree with Dubois (1986) that the species from Timor and Wetar are distinct.

Figures

Figure 5. Limnonectes timorensis. Female from near Eraulo, Ermera District (USNM [CMD 422], SVL 62 mm). Photo by Mark O'Shea.