Volume 49(25):319‑337, 2009 Snakes of the genus OXYRHOPUS (Colubridae: Squamata) in Colombia: taxonomy and geographic variation John D. Lynch1 ABSTRacT Four species of Oxyrhopus occur in Colombia, one (O. leucomelas) of which is Andean and the other three occur in lowlands. No geographic variation was detected in O. occipitalis but there is marked geographic variation in color pattern and scutellation for the widely distributed O. petola. Recognition of subspecies within O. petola is possible but appears to obscure more than it illuminates. The snake previously reported as O. melanogenys or O. aff. melanogenys is diagnosed as a previously unrecognized species. Keywords: Geographic variation; New species; Oxyrhopus. INTRODUCTION for Colombian specimens of Oxyrhopus leucomelas (Campbell & Lamar, 1989, 2004) and O. petola The current taxonomy of snakes of the genus (Renjifo & Lundberg, 1999). Oxyrhopus was established largely by Bailey’s ac- Published specimen-based studies for adjacent counts and keys to Oxyrhopus published in Peters & countries (Dixon & Soini, 1977, 1986; Duellman, Orejas’ (1970) catalogue. Either explicitly or implic- 1978, 2005; Savage, 2002; and Zaher & Caramas- itly, Bailey reported O. formosus, O. leucomelas, and chi, 1992) suggest that a critical review of specimens O. petola (all three subspecies) for Colombia. There of Colombian Oxyrhopus is needed. There was once have been no subsequent studies published of speci- (Niceforo María, 1942) active study of snakes pre- mens of Colombian Oxyrhopus although two reports served in Colombian collections but such activity of museum listings (without critical study of the largely ceased around 1970 although the collections specimens themselves) have appeared (Perez Santos themselves grew in volume. & Moreno, 1988; Sánchez et al., 1995). These two The four species of Oxryhopus known for Co- papers reported the same taxa as reported by Bailey lombia include two (O. leucomelas and O. petola) for but added O. melanogenys as well. These three publi- which taxonomic problems are minimal and two oth- cations provide only the merest of information about ers having accumulated literature as O. formosus (when species distributions and nothing about individual the Colombian specimens appear to be O. occipitalis) (or populational) variation, aspects that are central to or as O. melanogenys (when the snake appears to be the present contribution. Color illustrations (with- undescribed; in the text, prior to its formal descrip- out data other than collection locality) are available tion, I identify it as O. “melanogenys”). 1. Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Apartado Aéreo 7495, Bogotá, Colombia. 320 Lynch, J.D.: Colombian OXYRHOPUS Snakes of the genus Oxyrhopus are mostly band- rows on the nape as well as at midbody (curiously re- ed (termed coralsnake mimics by Campbell & Lamar, ported as 17 rows by Duellman, 2005, surely a vic- 1989, 2004) but at least two species (O. melanogenys tim of cut and paste) reducing to 17 (occasionally 16) and O. occipitalis) are red snakes with some head and/or rows anterior to the vent in most Oxyrhopus by means nape dark bands (although some specimens of O. me- of the loss of scale row 4 or the fusion of 3 + 4 at lanogenys have body bands). Oxyrhopus petola may be about ventral scute 113 to 150. Oxyrhopus leuucomelas so completely melanistic that inexperienced persons has 17-17-15 dorsal scale rows. confuse them with adult Clelia clelia (which does not exhibit preocular-frontal contact). In my survey of Number of supralabials and infralabials: Three Colom- Colombian collections, I found O. occipitalis confused bian Oxyrhopus have long heads whereas O. leucomelas with juvenile Clelia clelia and with Pseudoboa neuwiedii has a shorter head (Fig. 1) and this affects the number and found melanistic O. petola confused with Clelia. of labial scales. Excepting O. leucomelas, supralabials are normally 8 with 4 and 5 entering the orbit (rarely 9, with 5 and 6 entering the orbit, but not bilaterally). MATERials AND METHOds Excepting O. leucomelas, there are normally 10 infral- abials with 1-6 in contact with the chin shields. Using material from ten Colombian institu- tions (Colección de Zoología, Universidad de Tolima Contact between preoculars and frontal scale: The pre- [CZUT], Instituto Alexander von Humboldt [IAvH, oculars may exhibit sutural contact with the frontal or formerly the collection of INDERENA], Instituto de be separated from the frontal (Fig. 2). This character Ciencias Naturales [ICN], J. von Neumann (JVN], was used by Bailey to separate species as well as to Museo Herpetológico, Universidad de Antioquia characterize one subspecies of O. petola as different [MHUA], Museo de La Salle [MLS], Museo de Histo- from the other two subspecies. In order to score in- ria Natural de la Universidad de Cauca [UC], Museo dividuals, I generated a range of combinations (from Universidad Javeriana [MUJ], Museo de la Universi- each preocular well separated from the frontal to su- dad Industrial de Santander [UIS], and Museo de la tural contact with deformation [shape change] of the Universidad de Valle [UVC]), I located 272 specimens frontal on each side. Non contact between the preoc- of Oxyrhopus with at least locality data. From these ulars and frontal is seen in combinations 1-2 as well as specimens, scale counts, measurements, sex, maturity, asymmetrically in combination 3; combinations 4-5 location of the umbilicus (when neonates), and char- include various degrees of symmetrical contact). Oxy- acters of color patterns were collected by me. Lengths rhopus leucomelas, O. occipitalis, and Middle Ameri- of pale and dark body bands were measured in scale can populations of O. petola “sebae” are characterized lengths along the vertebral scale row. Aside from males partially by combinations 1 and 2. with everted hemipenes, all specimens were sexed by dissection of the base of the tail. When sample size per- Number of ventral and subcaudal scutes: These meris- mits, all means are reported as ± 1 standard error of the tic data were collected routinely but are rarely used mean to facilitate simple significance tests. My simple for species discrimination (but, see Dixon & Soini, significance tests consist of using twice the S.E. to ap- 1977; Duellman, 2005; Zaher & Caramaschi, 1992) proximate the 95% confidence intervals of the mean. because of sexual dimorphism and the frequency of specimens with incomplete tails. Characters pertinent to identification Coloration Scutellation Ontogenetic changes in color pattern: Oxyrhopus oc- cipitalis exhibits the most dramatic changes. Young Oxyrhopus have smooth scales with a pair of api- specimens have a yellow head and the body is banded cal pits and exhibit a posterior reduction in scale row black and nearly white whereas in adults, the snout is number (by two rows). The anal scute is entire. Sub- yellow, the rest of the head is black, and the body and caudals are paired. tail red (all red scales with black tips). Partially grown individuals exhibit the adult pattern but with faint re- Scale row formulae: Aside from the montane species, tention of the juvenile banded pattern concealed by O. leucomelas, and unusual specimens of other species the red pigment. Ontogenetic variation in O. petola with only 18 scale rows on the neck, there are 19 scale is less marked, consisting of black and yellow-white Papéis Avulsos de Zoologia, 49(25), 2009 321 bands in juveniles versus black and red bands in examined in this study are so melanistic that only the adults. With an increase in size, the pale bands (be- orange bands are evident. The other Colombian Oxy- ginning posteriorly and extending anteriorly) become rhopus normally (or always) exhibit a banded color orange and lastly red. The other two species do not pattern with only minor ontogenetic variation. exhibit comparable ontogenetic variation in patterns. Bailey (1970: 233) mentioned (and this is often re- However, in one neonate (ICN 11007) of peatedly uncritically in more general accounts of color O. petola that hatched soon after the egg was found pattern in O. petola) that large individuals of O. petola beneath a pile of African Palm fronds, the pattern digitalis are “often completely melanistic.” That is not consists of a single vertebral pale stripe from the nape the case as concerns the 17 O. petola “digitalis” (from to just anterior to the vent (1 scale wide). Another ne- 1 Colombia) here examined whereas uncommonly, onate (MLS 1374) has the first 4 /2 dorsal body bands O. petola “petola” is sufficiently melanistic to obscure fused to form a pale longitudinal stripe (1 scale wide), completely the banding pattern (ICN 6767, 10971, after which, the pattern reverts to dark dorsal bands 1 1 and 11064) and two specimens of O. “melanogenys” (64 /2 on body, 30 /2 on tail). Such striped Oxyrhopus FIGURE 1: Dorsal and lateral views of heads of (A-B) Oxyrhopus leucomelas, ICN 10025, and (C-D) Oxyrhopus vanidicus, ICN 10789. Scale equals 5 mm. 322 Lynch, J.D.: Colombian OXYRHOPUS FIGURE 2: Dorsal views of heads of snakes of the genus Oxyrhopus illustrating combinations of contact (or lack thereof) between preocular and frontal scales. (A) Scores of 1 (left side) and 2 (right side); (B) Scores of 4 (left side) and 6 (right side); (C) Score of 8. Snakes with scores of 2 and 4 or 2 and 8 were classed as score 3. Snakes with scores of 4 and 8 were classed as score 5. Those with scores of 6 and 8 were classed as score 7. are not found in the sample of adults, suggesting that Lengths of dark body bands: In Oxyrhopus petola, these variants are eliminated by natural selection. dark body bands exhibit different lengths along the length of the body, being longer anteriorly and Presence of triads: Triads (a sequence of black-white- shorter posteriorly. This is true as well for the snakes black-white-black limited by a partial or dorsally from the Llanos where one sees a high number of complete orange band) occur in one species of Oxy- body bands (and, as a consequence, a reduction of rhopus from Colombia.