Dipsas andiana (Boulenger)

CADLE, JOHN E. & MYERS, CHARLES W., 2003, Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae), American Museum Novitates 3409, pp. 1-48 : 25-31

Dipsas andiana (Boulenger)

Figures 7–8 , 12 top, 13–15; maps 2, 3

Leptognathus andiana Boulenger, 1896: 452 , pl. 23, fig. 2a–c. Type locality: ‘‘Quito, Ecuador’’ [probably a shipping point]. Holotype, BMNH 1946.1.20.12. Despax, 1911: 36. Werner, 1923: 197.

Leptognathus variegata: Steindachner, 1902: 108 (misidentification; specimen = Dipsas andiana based on details given).

Leptognathus andianus: Fowler, 1913: 169 (misidentifications; see footnote 17).

Sibynomorphus andiana: Parker, 1926: 206 .

Sibynomorphus andianus: Amaral, 1929: 195 .

[genus?] andiana: Dunn, 1933: 194 (compared with the new species Sibynomorphus nicholsi Dunn ).

Dipsas variegata nicholsi , part (Ecuadorian specimens only): Oliver, 1955: 70–71, photo (usage probably derived from Peters’ 1952 Ph.D. dissertation [= Peters, 1960a]). Peters, 1960a: 137; 1960b: 517. Peters and Orejas­Miranda, 1970: 90. Miyata, 1981: 16. Pérez­Santos and Moreno, 1991: 161.

Dipsas oreas , part: Peters, 1960a: 92; 1960b: 517. Peters and Orejas­Miranda, 1970: 88. Leptognathus andiana listed as a synonym.

DIAGNOSIS: Dipsas andiana is a pale brown or grayish snake with a distinctive contrasting pattern on the head and dorsum. The head is relatively unmarked except for a bold blackish brown Π­ shaped or inverted Vshaped marking extending from the anterior edge of the frontal to the neck (fig. 8). Dorsal markings consist of a series of large round, elliptical, or irregular dark blotches on each

TABLE 3 Measurements (in mm) and Standard Characters in Dipsas oreas a

side, each with a narrow pale border. Corresponding blotches from each side occasionally meet middorsally, in which case there is a definite constriction at the vertebral scale row. Anteriorly, blotches tend to be opposite one another, whereas posteriorly they tend to alternate. Interspaces between the blotches are broader than the blotches (in some specimens 2–2 ½ ×) for the entire length of the body; anteriorly, the interspaces tend to be narrower than posteriorly. Dipsas andiana has a high number of ventrals (185–201) and subcaudals (53, 91–106; 4♀, 82–83). See table 2 for character summary of specimens examined.

Other species of Dipsas in western Ecuador include D. gracilis , D. oreas auctorum (including D. ellipsifera and D. elegans ; see Orcés and Almendáriz, 1987), and D. temporalis . These species lack the distinctive head marking of D. andiana , although they usually have extensive dark markings on the head. Dipsas gracilis and D. temporalis are similar to D. andiana in having high numbers of ventrals and subcaudals; however, these are distinctly banded snakes in which the bands are much broader than the inter­ spaces, are not round or elliptical, and lack distinct pale borders. The bands in D. gracilis extend across the venter, whereas the blotches in D. andiana end on the lateral edges of the ventrals. Dipsas ellipsifera and D. elegans have narrow rectangular blotches or bands with light centers and straight edges (Peters, 1960a: pl. 4a; Kofron, 1982a: fig. 1). Characters distinguishing D. andiana and D. oreas s.s. are given above, where these two species are compared in more detail.

DESCRIPTION

Largest male 648+ mm total length (tail incomplete), 488 mm SVL; largest female 843+ mm total length (tail incomplete), 673 mm SVL. Body strongly compressed. Tail 23–26% of total length. Dorsal scales in 15– 15–15 rows. Width of vertebral scale row slightly greater than that of paravertebral row in adults, much greater in juveniles. Ventrals 185–196 with broad overlap between the sexes (table 2; the range extends to 201 for males if we have correctly inferred the identity and sex of Steindachner’s [1902] specimen). Anal single. Subcaudals 83–106, av­ eraging 95 in males, 83 in females. Loreal and prefrontal bordering the anterior edge of eye. Head scales highly variable: postoculars 1–3, primary temporals 1–3, secondary temporals 2–5, supralabials 8–10 (usually 4–5 or 3–5 bordering the eye), infralabials usually 10 or 11 (range 9–12). Either one or two pairs of infralabials in contact behind the mental, with the following frequencies in our sample: first infralabials in contact (N = 1), first two in contact (7), one infralabial contacts two on the opposite side (2). Maxillary teeth 12–13 (N = 9); dentary teeth 20 in one specimen ( KU 110312) .

COLOR IN LIFE: We have not seen living specimens of Dipsas andiana . A color photograph of a specimen we refer to D. andiana (Pérez­Santos and Moreno, 1991: photo 74 of ‘‘ Dipsas sp. ’’) shows the dorsal ground color of the head and body as being pale brown (almost tan). The head marking and dorsal blotches are black, with narrow borders of white to pale brown. Steindachner (1902) described his specimen of ‘‘ Leptognathus variegata ’’ as having reddish brown dorsal blotches with bright yellow borders, a sulfur­yellow ground color on the head, and a dirty yellowish venter.

white; top of head brown with very dark brown markings; venter pale yellow anteriorly becoming nearly gray posteriorly; dark brown flecking on venter.

KU 164210–164211 (WED 48442–48443): Dorsum pale brown with black blotches narrowly outlined by cream. Throat and anterior part of venter creamy white. Rest of venter grayish white with black spots. Iris grayish tan. Tongue black with cream tip.

Color notes are associated with several specimens we examined (from field catalogs of John D. Lynch and William E. Duellman):

KU 132503 (JDL 6612): Dorsum dull brown with dark brown saddles edged by very pale brown; the edging of the saddles takes on a yellow cast near the ventrals anteriorly; iris gray; venter yellow brown becoming pale brown­gray toward tail; throat creamy yellow.

KU 132504 (JDL 7813): Ground color brown (more grayish posteriorly); spots dark brown, edges of spots outlined with very pale yellow; iris gray­

COLOR AND PATTERN IN PRESERVATIVE: Dorsal ground color of head and body light brown to grayish. Top of head with blackish Π­ shaped marking from prefrontal/frontal border to the neck. Head generally with few distinct markings apart from the Π­ shaped mark; sutures and scale edges may be outlined with black (apparently more prominent in juveniles than in adults). The head marking normally is not connected to the first pair of neck blotches (compare D. nicholsi ), except for AMNH 79013, in which the marking is broadly confluent with the neck blotch on the right side (similar to the pattern in D. nicholsi ) and very narrowly connected on the left side (fig. 15); the color pattern and scutellation of AMNH 79013 are otherwise characteristic of andiana .

Dorsum with 18–25 elliptical lateral blotches, each taller than wide and with a narrow pale border. Width of blotches anteriorly (first pair after the neck blotches) 3.5– 5 scales, at midbody 3–4 scales, and just anterior to vent 2.5–3.5 scales. The interspaces are as broad to much broader (2–2.5×) than the dorsal blotches for the entire length of the body. Often, but not universally, the first pair of blotches on the neck is elongate. Blotches vary from rather round to more irregular or vertical (figs. 13–14). Dorsal blotches extend only to the outer edges of the ventral scales. Elongate blackish streaks and/or small irregular spots frequently occur between the dorsal blotches (e.g., figs. 7, 13) and are more prominent on the anterior half of the body than posteriorly. Pale borders to the dorsal blotches are obvious in nearly all specimens, but are obscure in some, especially posteriorly, possibly a preservation artifact.

The venter is often without distinct markings, but may have a variable amount of dark streaking or spotting (fig. 13). The venter is relatively unmarked in the holotype, KU 132503, AMNH 35955 , and MCZ 166543 , but is streaked or partly checkered with dark brown in KU 164211 and AMNH 35949 . These variations do not seem correlated with size. The tail is patterned similar to the body dorsally and ventrally .

In juveniles the blotches and head marking are dark chocolate brown, whereas the ground color is light grayish brown; this is a more contrasting pattern than in adults. In larger specimens the markings tend to be dark (but not chocolate) brown, whereas the interspaces are medium brown. Juvenile specimens also seem to have more dark suture lines and markings on the head than do adults. However, this is not universal. For example, MCZ 166543 (total length 505 mm and presumed to be adult) has many dark suture lines, whereas these markings are much reduced in KU 132503 (total length 622).

HEMIPENIS

The hemipenes of KU 132503 were only partially everted when the specimen was preserved. Using a modification of the technique of Pesantes (1994; Cadle, 1996), the left organ was removed, fully everted, and inflated with colored jelly. Although the eversion was successful, the overall inflation of the organ is probably somewhat less than in a fully inflated organ. Nonetheless, a complete description is possible.

The hemipenis is slightly bilobed distally and fully capitate. The major retractor muscle is divided for about 5 mm at its insertion (the length of the division probably varies depending on the extent of eversion of the organ). The sulcus spermaticus divides just within the capitulum, with the branches going to the periphery of the tips of each lobe in centrolineal orientation.

The capitulum is entirely calyculate and the calyces are densely ornamented with fleshy papillae. The calyces between the branches of the sulcus spermaticus are more weakly developed than those on the rest of the capitulum (i.e., the ridges forming the calyces are lower); however, the papillae in this area are as well developed as elsewhere on the capitulum.

Just proximal to the capitulum is a single transverse row of large, more or less straight, hooked spines encircling the entire organ. Between these spines and the groove delim­ iting the capitulum on the asulcate side of the organ is a partial row of smaller, straight, hooked spines. The entire organ proximal to the enlarged spines is ornamented with spinules all around.

The sulcate side of the organ below the encircling row of enlarged spines bears additional ornamentation. A patch of curved, hooked spines is present on each side of the distal end of the undivided portion of the sulcus spermaticus (i.e., just proximal to the encircling hooked spines); the patch comprises four spines on one side, seven on the other. Tapering away from each patch toward the asulcate side of the organ are several similar spines in an irregular row.

There is a laterally positioned, elongate nude pocket below the capitulum (similar to the position in Dipsas nicholsi in fig. 6, bottom); the middle of the pocket is bordered on each side by rounded lobes. The pocket curves slightly mediad onto the asulcate surface distally, terminating below a pair of enlarged, hooked spines. There is another pair of enlarged hooked spines lying towards the asulcate side of the organ, adjacent to the lobe bordering the elongate pocket (these spines seemingly corresponding to the irregular row of enlarged spines on the asulcate side in D. nicholsi ).

The hemipenis of Dipsas andiana is similar in overall morphology to that of D. nicholsi and the other species of Dipsadini discussed previously (see description of D. nicholsi hemipenis). There are minor differences between the organs of D. nicholsi and D. andiana (see below under Comparison of Dipsas andiana and Dipsas nicholsi ).

DISTRIBUTION AND NATURAL HISTORY

Dipsas andiana occurs along the Pacific versant of western Ecuador —approximately from the equator to latitude 2° South —in a known elevational range of 5–1140 m (maps 2, 3) .

Little is known of the natural history of this species. Field notes by John D. Lynch (for KU 132503–132504) and William E. Duellman (KU 164210–164211) include the following comments: KU 132503 was ‘‘coiled up in Costus [ Costaceae : Zingiberales ] leaves in open area by river about 1 m

Map 2. Locality records for Dipsas andiana in western Ecuador. Localities: (1) Puerto Quito; (2) Santo Domingo de los Colorados ( Despax, 1911); (3) Dos Ríos; (4) Las Palmas; (5) Babahoyo ( Steindachner, 1902); (6) Balsapamba. See also map 3.

off the ground.’’ KU 132504 was ‘‘sleeping (?) by night on fern frond along side of road.’’ KU 164210 and 164211 were ‘‘coiled in branch of trees ca. 2.5 m above ground at night.’’ The KU specimens were collected in April, July, and August in the early to mid­ 1970s; MCZ 166543 was collected in September 1983 .

See also Lynch’s note on Dipsas andiana under Dipsas nicholsi , in Defensive Behaviors in the Dipsadini .

Oliver (1955) gave a sense of the diverse Central American and South American reptiles that once made their way to the banana terminal in New York Harbor and even to local grocery stores. Widespread adoption of the right side (compare fig. 15 with Oliver, 1955: 71, photo lower right).

Figures

Fig. 7. Dipsas andiana (Boulenger). Dorsal and ventral views of the holotype (BMNH 1946.1.20.12) from an unknown locality in Ecuador.

Fig. 8. Dipsas andiana (Boulenger). Close­up of head of holotype. The characteristic Π­shaped pattern differentiates andiana from Dipsas oreas and hints at a possible relationship with Panamanian Dipsas nicholsi.

Fig. 12. Comparison of head shapes and color patterns in Dipsas andiana and Dipsas oreas at equivalent magnifications. Top: D. andiana (KU 132503, 622 mm total length). Bottom: D. oreas (KU 142803, 629 mm total length). Dipsas andiana has a stereotypical Π­shaped pattern on the dorsal surface and is relatively unmarked otherwise, whereas D. oreas has irregularly and heavily pigmented dorsal and lateral surfaces of the head. Dipsas oreas also has angular canthal and supratemporal regions and a relatively longer postorbital region than does D. andiana.