Dipsas oligozonata (ORCÉS & ALMENDÁRIZ, 1989)
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Dipsas oligozonata
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| Higher Taxa | Colubridae (Dipsadinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes) |
| Subspecies | |
| Common Names | |
| Synonym | Sibynomorphus oligozonatus ORCÉS & ALMENDÁRIZ 1989 Sibynomorphus oligozonatus — CADLE 2007: 191 Sibynomorphus oligozonatus — WALLACH et al. 2014: 670 Dipsas oligozonatus — ARTEAGA et al. 2018 Dipsas oligozonata — ARTEAGA et al. 2023 |
| Distribution | Ecuador Type locality: ‘‘Zhila (2,250 m) 79°17’26”W, 03°39’45”S, parroquia Oña, cantón Girón, Provincia Azuay [Ecuador].’’ |
| Reproduction | oviparous |
| Types | Holotype: MEPN (also as EPN) 3612; additional specimens in AMNH, BMNH, MUSM |
| Diagnosis | Diagnosis: Sibynomorphus oligozonatus is a gray to grayish brown snake with broad dark crossbands anteriorly (narrowing and becoming broken into dorsal and lateral blotches posteriorly). Anterior crossbands are much broader than the interspaces and have regular, vertical edges and sometimes are offset. Posterior crossbands are usually much narrower than the interspaces. The venter is unmarked or has irregular dark speckling or spotting concentrated posteriorly. The head is foreshortened and blunt. The species has a low number of supralabials (6 or 7) and maxillary teeth (12–15). Males of S. oligozonatus have a low number of ventrals (145 in two males, 163 in another) and relatively long tail (24–26% of total length); these characters in the single known female (177 and 22%, respectively), are typical of some other species of Sibynomorphus (see Table 1). Scrocchi et al. (1993) questioned whether Sibynomorphus oligozonatus was diagnosable from S. vagrans on the basis of the characters given in the original description. However, these two species differ in head shape and proportions, as well as several scale characters. Sibynomorphus oligozonatus has a short head and blunt snout (Fig. 4), lacks preoculars in the known specimens (i.e., the preocular is fused with the prefrontal and only a loreal is present between the eye and posterior nasal), and has six or seven supralabials and fewer than 70 subcaudals. Sibynomorphus vagrans has a more elongate head and more pointed snout (compare Fig. 4 with Figs. 30, 31), has a preocular in addition to a loreal (occasionally 2 preoculars and a loreal), and has eight to 10 supralabials and more than 70 subcaudals (Table 1). Sibynomorphus oligozonatus differs in color pattern from S. oneilli (see Figs. 8– 10). Both species have dark crossbands that are broader anteriorly than posteriorly (some S. oneilli lack bands; see following species account). In S. oligozonatus, the anterior crossbands are twice or more as broad as the pale interspaces, whereas on the anterior body in S. oneilli, the interspaces are about as broad as, or broader than, the dark crossbands. Sibynomorphus oneilli has a bold pattern of dark markings in an irregular checkerboard pattern or paired spots on each ventral plate, whereas the venter of S. oligozonatus is relatively unmarked (AMNH 110587 does have irregular dark speckling all over the venter and some larger spots that tend to be concentrated laterally, but this pattern does not resemble the heavily spotted venter of S. oneilli; see Figs. 9, 10, 12). Sibynomorphus petersi occasionally has relatively broad anterior crossbands reminiscent of, but less regular than, those of S. oligozonatus. Sibynomorphus petersi has a preocular above the loreal (preocular absent in S. oligozonatus) and usually has eight supralabials (six or seven in S. oligozonatus). In addition, male S. petersi have more ventrals (164–183) than S. oligozonatus. Sibynomorphus petersi generally has a strongly patterned venter (Fig. 13 and following) compared with the relatively less patterned venter of S. oligozonatus. Sibynomorphus oligozonatus differs from S. vagus in color pattern: broad anterior crossbands having regular, more or less vertical borders in S. oligozonatus versus either nonbanded (a vague network or fine reticulations) or with narrow, poorly formed, and irregular crossbands in S. vagus. Sibynomorphus vagus has fewer ventrals in females, has a preocular scale, usually has a single primary temporal, and has seven or eight supralabials. Sibynomorphus oligozonatus differs from S. williamsi in having fewer ventrals (males: 145–163 vs. 173–182; females: 177 vs. 181–188), in head shape (oligozonatus: head slightly broader than neck, short and blunt; williamsi: head broader than neck, longer and acuminate), and in some aspects of color pattern. In S. williamsi, the first dorsal crossband usually encroaches broadly onto the nuchal region (see Figs. 41, 42), whereas in S. oligozonatus, the first crossband is separated narrowly from the head by a distinct narrow pale collar (Fig. 4). The dorsal bands in S. williamsi are bold and distinct the whole length of the body and tail (even when fragmented into a dorsal and lateral series of blotches), whereas in S. oligozonatus, the anterior bands are much bolder than the posterior ones. In S. oligozonatus the dorsal blotches on the posterior body are slightly to much narrower than the pale interspaces; the posterior dorsal blotches in S. williamsi are equivalent to or wider than the pale interspaces. The color pattern of the BMNH and AMNH specimens of Sibynomorphus oligozonatus is reminiscent of some specimens of Dipsas oreas, which perhaps led Parker (1938) to refer the BMNH specimen to that species (as ‘‘Dipsas mikanii oreas’’). However, D. oreas usually has a pair of large oval dark irregular spots on the dorsoposterior portion (primarily parietal scales) of the head (Cadle, 2005: 101–108), a strongly compressed body, and a relatively much larger eye (compare Fig. 4 with Cadle, 2005, fig. 21). The relative eye diameter of the BMNH specimen of S. oligozonatus, the only adult with an undamaged head, was 0.51% of SVL, whereas for 12 adult D. oreas, the eye averaged 0.73 0.049% of SVL (range: 0.64–0.78%). Males of S. oligozonatus can be distinguished from D. oreas by having fewer ventrals (144–163 vs. 167–184 in D. oreas) and subcaudals (66–68 vs. 82–91 in D. oreas). The female referred to S. oligozonatus is similar to females of D. oreas except for a slightly lower subcaudal count (66 vs. 70–83) and the previously mentioned aspects of color pattern and body form. See Table 2 and Cadle (2005, table 1). (Cadle 2007) Unfortunately we had to temporarily remove additional information as this was scraped by multiple AI companies who sell that data to their customers. These details, e.g. detailed descriptions or comparisons (about 6635 characters) are available for collaborators and contributors. Please contact us for details. |
| Comment | Only known from the holotype. Synonymy: Maybe a synonym of S. vagrans (fide SCROCCHI et al. 1993). Not listed in Zoological Record. Distribution: not in Peru fide IUCN assessment. Diet: primarily molluscs (T. de Lema, pers. comm., 16 Oct 2015). Habitat: fully arboreal (Harrington et al. 2018). |
| Etymology | Named after Greek oligos (ὀλίγος), little, small, insignificant + Latin zonata, encircling band/marking. [“...El nombre, tomado del griego, se refiere a las escasas fajas transversas, mucho menos numerosas de lo que es usual en el género...”]. (from Esteban Lavilla, pers. comm., May 2024) |
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