Tropical Natural History 17(1): 25-52, April 2017 2017 by Chulalongkorn University On the Validity of Pareas macularius Theobald, 1868 (Squamata: Pareidae) as a Species Distinct from Pareas margaritophorus (Jan in Bocourt, 1866) SJON HAUSER 71 Wiang Phing Road, Mueang, Chiang Mai 50100, THAILAND * Corresponding Author: Sjon Hauser ([email protected]) Received: 13 June 2016; Accepted: 23 December 2016 Abstract.– The genus Pareas Wagler, 1830, consists of about fifteen species of small snail-eating snakes distributed in China, South and Southeast Asia. Until recently, two Pareas-species ornamented with characteristic bicolored spots were recognized, P. margaritophorus (Jan in Bocourt, 1866) and Pareas macularius Theobald, 1868. However, P. macularius was synonymized with P. margaritophorus by Huang (2004), reducing the speciosity of the bicolored-spotted snail-eaters to a single species. This claim was tested by examining more than 60 fresh road-killed specimens of bicolored-spotted snail-eaters from northern Thailand. They were either completely smooth-scaled, or had rows of weakly keeled dorsals. The smooth-scaled specimens differed significantly from the keeled-scaled in a number of characters. The holotype of P. margaritophorus corresponded closely to the smooth-scaled specimens, whereas the holotype of Pareas macularius corresponded to the keeled- scaled ones. It was, thus, shown that P. macularius is a valid species and the synonymization as claimed by Huang (2004) was refuted. P. macularius is distinguished from P. margaritophorus by having the 7–13 most median rows of dorsal scales feebly keeled at midbody, by the form and color of the nuchal collar, its larger size, the larger number of ventral shields, and the high incidence of an intense black blotch on the last, largest supralabial. A preliminary distribution map for the two species is provided. KEY WORDS: northern Thailand, Pareas macularius, Pareas margaritophorus, Southeast Asia, taxonomy central mental groove separating the paired INTRODUCTION chin shields. Pareid snake taxonomy is an ongoing controversy. The genus Pareas The snail-eating snakes of South, East differs from the other genera of the family and Southeast Asia are presently considered by having 15 rows of dorsal scales, the to constitute the distinct family of Pareidae presence of pre- and suboculars (in most together with two other genera (Pyron et al., species), and characteristics of the chin 2011; Wiens et al., 2012; Reptile Database; shields (Grossman and Tillack, 2003). It see Savage [2015] for the correct spelling of consists of 14 recognized species at present the family name). Most species have a (Reptile Database). number of adaptations related to preying on Three of them, Pareas carinatus Boie, snails and slugs (Wall, 1909), such as a 1828, P. hamptoni (Boulenger, 1905), and blunt snout, and a specialized feeding- P. margaritophorus (Jan in Bocourt, 1866) apparatus, including an asymmetric are currently recognized from northern dentition related to extracting (dextral) Thailand (Reptile Database). Besides these, snails from their shells (Parker and P. macularius Theobald, 1868 had Grandison, 1977; Hoso et al., 2007, 2010; previously been recognized in this and Danaisawadi et al., 2015, 2016). Another adjacent regions as well, but Huang (2004) morphological characteristic is the lack of a 26 TROPICAL NATURAL HISTORY 17(1), APRIL 2017 synonymized this nominal species with P. Snake’ (e.g. Cox 1991; Cox et al. 2012) or margaritophorus. ‘Black-spotted Slug Snake’ (Nabhitabhata et Prior to Huang’s (2004) synonymization, al. 2004); the colloquial Thai names ngu kin P. margaritophorus and P. macularius had thak chut khao (‘White-spotted Slug-eating been considered to occur throughout much Snake’) for P. margaritophorus and ngu kin of mainland Southeast Asia and parts of thak chut dam (‘Black-spotted Slug-eating southern China. Both were described as Snake’) for P. macularius (Cox 1991; purplish-grey or brownish-grey snakes, Jintakune 2000) are translations of those rarely exceeding 60 cm in total length. In confusing English names. visual appearance, they are particularly The original descriptions of the two conspicuous by having an ornamentation of nominal species in the mid-19th century numerous black-and-white spots. These were not very clear. The description of spots are exactly the size of a dorsal scale: Pareas macularius (Theobald, 1868) was the anterior tip of such a scale is white, and particularly confusing because two of the the remaining, posterior portion is black. five specimens examined by Theobald did These bicolored spots contrast conspicuously not appear to represent bicolored-spotted with the ground color of the skin which is slug snakes at all (Sclater, 1891; Das et al., greyish (densely speckled with fine dark 1998). However, in the classic work of grains). Some bicolored spots appear to be Boulenger (1896), P. margaritophorus and completely black, since the tiny white P. macularius emerged as two clearly anterior tip of each scale is completely distinct species. In the meantime, three covered by the posterior black portion of the rather similar species of snail-eaters were preceding scale. These bicolored spots are described and considered valid in not randomly distributed, but usually form a Boulenger’s work. Another bicolored number of rather narrow, transverse series. spotted snail-eater was also added to the list Even when both P. margaritophorus and P. published in 1935 by R. Bourret. macularius were considered as valid, they The situation was completely reversed could not be distinguished by the shape or when Smith (1943) synonymized one of distribution of these spots. Superficially, these newer species with P. margaritophorus, therefore, the two nominal species showed and three others with P. macularius. Of the considerable morphological similarity by previous six species of ‘spotted snail- the presence of at least a good number of eaters’, only two remained. The final blow conspicuous bicolored spots. to the speciosity of the spotted snail-eaters These spots have given rise to the came sixty years later when Huang (2004) scientific names of both Pareas synonymized P. macularius with P. margaritophorus (the specific nomen margaritophorus, resulting in only one valid meaning ‘pearl carrier’) and Pareas species. This complex history is macularius (the specific nomen meaning summarized in Fig. 1. ‘spotted’). Confusing colloquial English and Huang’s synonymization coincided with Thai names also referred to these spots: In another publication, in which the authors English, P. margaritophorus was known as also ‘believe that Pareas macularius ‘White-spotted Slug Snake’ (e.g. Cox et Theobald, 1868, is a synonym of P. al.1998, Nabhitabhata et al. 2004), whereas margaritophorus (Jan, 1866)’ (Guo and P. macularius was known as ‘Spotted Slug Zhao, 2004). Authors of these works seem HAUSER — ON THE VALIDITY OF PAREAS MACULARIUS 27 FIGURE 1. History of descriptions of new species of ‘spotted snail-eaters’ and their subsequent synonymizations. to have paid little attention, if any, to Smith [southeastern Myanmar], respectively). (1943), and most of other subsequent works, Nevertheless, Huang’s (2004) account was including Taylor (1965), in which P. adopted in most subsequent Chinese studies, margaritophorus and P. macularius were such as Guo and Deng (2009) and Guo et al. apparently well-defined against each other. (2011), although a few others continued to In Chan-ard et al. (1999), six pictures of recognize P. macularius as valid (e.g., Yang spotted snail-eating snakes were published, and Rao, 2008). In the meantime, Vogel each of which was identified correctly as (2009) expressed his conservative stance either P. margaritophorus or P. macularius. against Huang’s (2004) claim due to the In this period, the validity of each of the two absence of examination of type materials species was not questioned by any therein. Notwithstanding these views, the taxonomists. Living specimens that before synonymization has been gradually and Huang’s (2004) synonymization would have broadly approved by authors in subsequent been identified as P. margaritophorus, and publications, leading to the removal of P. P. macularius, are shown in Fig. 2, macularius from most recent lists of respectively Fig. 3. recognized Pareas species, including that in Huang’s synonymization was made the reputed Reptile Database (see above). In solely on the basis of information from a number of collections, specimens initially Smith’s (1943) description and data from identified as P. macularius were renamed P. Chinese specimens, i.e., without examining margaritophorus. In at least one study, such holotypes of P. margaritophorus and P. renamed specimens were subjected to DNA macularius, despite their non-Chinese extraction and analysis, resulting in the origins (“Siam” [Thailand] and Martaban conclusion that ‘Pareas margaritophorus’ 28 TROPICAL NATURAL HISTORY 17(1), APRIL 2017 showed remarkably large sequence often fails to result in evertion of divergences (Guo et al., 2011). hemipenes. However, the sex of many In the present paper, I resurrect P. specimens could be determined with high macularius as a valid species based on the probability by the relative tail length. analysis of morphological data of many Subsequently, a note was made on the road-killed specimens found in northern habitat of the collecting site, which was Thailand. specified as the distance (by road) in kilometers to the nearest large village