Friday, December 25, 2015

[Herpetology • 2014] New Data on the Morphology and Distribution of the Enigmatic Schouteden’s Sun Snake, Helophis schoutedeni (de Witte, 1922) from the Congo Basin


FIGURE 2. Photos of a living specimen of Helophis schoutedenifound in 2012 in Kinshasa.
 
From top left, clockwise: dorsal view of the specimen; ventral view of the specimen; dorsolateral view of the forepart of the animal; ventral view of the head. 

Abstract

The Schouteden’s sun snake is the sole representative of its genus, and was originally described by the Belgian herpetologist Gaston-François de Witte as a colubrid, Pelophis schoutedeni (de Witte 1922). Twenty years later, the new generic name Helophis was established by de Witte & Laurent (1942) because the generic name Pelophis was preoccupied by Pelophis Fitzinger, 1843 [type species: Brachyorrhos (now Enhydris) alternans Reuss, 1834]. De Witte (1922) and de Witte & Laurent (1942) gave data on two syntypes (Fig. 1), which are preserved in the herpetological collection of the Royal Museum for Central Africa in Tervuren, Belgium. One, RMCA R.2468, was found in Tondu (at Lac Tumba, Équateur Province, Democratic Republic of the Congo = DRC), while the other, RMCA R.2469, was collected in Kwamouth (“Moyen-Congo”, now Bandundu Province, DRC). Both were collected by Henri Schouteden in 1921. In the original description, no information was given about the sex of the syntypes. De Witte & Laurent (1942) reported a third specimen (RMCA R.11551) from Léopoldville (today Kinshasa), which was collected in 1937 by Henrard. Since then, this snake species was almost forgotten, and the genus has remained monotypic. To our knowledge, no photographs of living specimens of this species have been published so far. In general, very little is known about the distribution, biology, conservation status or even the phylogenetic relationships of this vividly colored snake species. Although several works listed Helophis schoutedeni as being part of the Congo Basin (DRC) snake fauna (e.g. Kusamba 1990; Meirte 1992; Trape & Roux-Estève 1995; Broadley 1998) sometimes including a basic identification key, no new information was given. Moreover, no recent field guides of the Central African region (e.g., Chippaux 2006) include this snake species. Regarding its classification, Broadley (1998) considered it as a natricine species (Natricinae) while in The Reptile Database (Uetz & Hošek 2013) it is listed as Colubridae incertae sedis, similarly like in Pyron et al. (2013), where Helophis was missing from their phylogenetic meta-analysis.

Keywords: Congo Basin, sun snake, Helophis schoutedeni, new data


FIGURE 2. Photos of a living specimen of Helophis schoutedeni, found in 2012 in Kinshasa.
From top left, clockwise: dorsal view of the specimen; ventral view of the specimen; dorsolateral view of the forepart of the animal; ventral view of the head.

Discussion:
 Since the majority of distribution records are coming from the Eastern Congolian swamp forests upriver the Congo River and its tributaries, it opens a question about the origin of the specimens collected in Léopoldville/Kinshasa. The strong current of the Congo River often carries floating vegetation islands, which occasionally introduce fauna and flora from the upriver into the Lower Congo region (MC, pers. observ.). This phenomenon might also explain the findings of the Schouteden’s sun snake outside the swamp forests. Ecologically, Helophis schoutedeni is obviously a semi-aquatic snake as indicated by its dorsally-oriented nostrils, narrow triangular internasals, small eyes with round pupil and stout body. Furthermore, during a short period in captivity, the observed Schouteden’s sun snake preferred to stay in water. Helophis shows an extreme similarity to the genus Hydraethiops, as de Witte (1922) indicated in the original description. He, however, also mentioned that two differences between them, i.e., the double internasals and the lower number of teeth in Helophis, justified the erection of a new genus. Boulenger (1904), in his description of Hydraethiops laevis, indicated, based on the observations that he made on the two syntypes, that the internasals could be divided or semi-divided. The third known individual of Hydraethiops laevis, from the Chaillu Massif in Gabon, shows a single internasal (Pauwels et al. 2002). The condition of the internasals is variable in Hydraethiops melanogaster as well; for example, the individual illustrated by de Witte (1962) shows a partly divided internasal. Helophis shows 16 or 17 maxillary teeth (de Witte 1922; Meirte 1992), while Hydraethiops shows 20 to 22 (Chippaux 2006). The internasals’ condition in Helophis is thus not a character  separating  it  from  Hydraethiops.  The  slightly  lower  number  in  maxillary  teeth  does  not  justify  alone  the  placement in a distinct genus. Pending a genetic analysis, the genus Helophis could be regarded as valid while doubtful with  regard  to
,  but  at  least  its  placement  within  Natricinae  along  with  Hydraethiops  as  proposed  by  Broadley (1998) seems justified on a morphological basis


Zoltán T. Nagy, Vaclav Gvozdik, Danny Meirte, Marcel Collet and Olivier S. G. Pauwels. 2014. New Data on the Morphology and Distribution of the Enigmatic Schouteden’s Sun Snake, Helophis schoutedeni (de Witte, 1922) from the Congo Basin. 
 ZOOTAXA. 3755(1):96-100. DOI: 10.11646/zootaxa.3755.1.5

No comments:

Post a Comment