Dendrophidion brunneum (Günther), Gunther

Cadle, John E., 2010, Systematics, natural history, and hemipenial morphology of Dendrophidion brunneum (Günther) (Serpentes: Colubridae), a poorly known snake from the Andes of Ecuador and Peru, Zootaxa 2433, pp. 1-24 : 3-8

Dendrophidion brunneum (Günther)

Herpetodryas brunneus Günther 1858: 116 (type locality: “Guayaquil” [ Ecuador]). Holotype: BMNH 1946.1.12.98 fide Peters (1960: 514), a female fide Boulenger (1894: 16). Günther 1859: 412 (“Andes of western Ecuador ”). Günther 1863: 358 and plate 6, fig. A (presumably based on the holotype). Günther 1885 –1902: 128.

Herpetodryas brunneus (non Günther, 1858) (misidentifications): Salvin “1860 ” [1861]: 456 ( Guatemala). Cope 1868: 105 (Guayaquil and “Valley of Quito”). Duméril et al. 1870 –1909: 732 (reference to Jan & Sordelli 1860 –1881: livraison 31, plate 3, figs. 1–2: “ Herpetodryas dendrophis ” from “Guayaquil” and “ Ecuador ”). Boulenger 1882: 462; 1891: 132 (Guayaquil). Garman 1892: 90 (Guayaquil and vicinity). See discussion of doubtful records under Distribution herein.

Herpetodryas dendrophis var. brunneus (non Günther, 1858) (misidentifications): Jan 1863: 81. Specimens from western lowland Ecuador: La Maná [Cotopaxi Prov., ca. 250 m; ca. 0 0°59' S, 79°17' W] and Esmeraldas [Esmeraldas Prov., 0 m; 0 0°59' N, 79°42' W]. See discussion of doubtful records under Distribution herein.

Masticophis brunneus (non Günther, 1858) (misidentifications): Cope 1868: 105. Specimens from Guayaquil and “Valley of Quito”. Probably = Dendrophidion percarinatum . See discussion of doubtful records under Distribution herein.

Drymobius dendrophis (part): Boulenger 1894: 15. Referred specimens include the holotype of Herpetodryas brunneus Günther.

Dendrophidion dendrophis brunneus (non Günther, 1858) (misidentification): Parker 1938: 443 (= D. dendrophis (Schlegel) sensu stricto). See discussion of doubtful records under Distribution herein.

Dendrophidion brunneum: Peters 1960: 514 . Lieb 1988: 171. Almendáriz 1991: 143. Pérez-Santos & Moreno 1991: 133. Kuch & Freire 1993: 106.

Dendrophidion brunneus: Peters & Orejas-Miranda 1970: 80 . Miyata 1982: 16.

Diagnosis. Dendrophidion brunneum is characterized by 17 midbody scale rows, reducing to 15 (rarely 13) posteriorly; dorsocaudal reduction from eight to six anterior to subcaudal 25; ventrals fewer than 155 in males, fewer than 170 in females; subcaudals fewer than 160. Tail 40–44 % of total length (67–80% of SVL) in males, 38–41% of total length (61–71% of SVL) in females; and dorsal coloration usually green to olive (brown or bluish in some specimens) and usually without stripes or crossbars (anterior body, especially the head, often with brighter hues or a different color from the posterior body) ( Fig. 1 ). The everted hemipenis is unique among known hemipenes of Dendrophidion in having a greatly expanded, globose distal region and a very short segment of the hemipenial body proximal to the expanded region (see Hemipenial Morphology of Dendrophidion brunneum ).

Scale counts of many species of Dendrophidion overlap extensively ( Lieb 1988: Table 1 ) and color patterns are often the most reliable characters for identifications. In D. dendrophis , D. nuchale , and D. vinitor the dorsocaudal reduction from eight to six occurs posterior to subcaudal 25. Of the species in which the dorsocaudal reduction occurs anterior to subcaudal 25, D. paucicarinatum has more than 175 ventrals ( Lieb 1988), D. bivittatum (Duméril, Bibron, & Duméril) has broad blackish paravertebral stripes and distinct lateral stripes on the posterior body and tail, and D. boshelli Dunn has only 15 midbody scale rows. Confusion of D. brunneum is most likely to be with the two species distributed in the same general region in western Ecuador, D. nuchale and D. percarinatum ( Lieb 1988, 1991a, 1996). Both of these species occur primarily in the lowlands, whereas D. brunneum is primarily a species of the Andean slopes (see Distribution). Dendrophidion nuchale usually has a black nuchal collar, often has pale ocelli on the posterior body, and the dorsocaudal reduction occurs posterior to subcaudal 25 ( Lieb 1988, Savage 2002). Specimens of D. percarinatum from western Ecuador usually have distinct narrow (<1 scale wide) pale crossbands anteriorly (sometimes extending for a greater portion of the body) and a variably complete longitudinal dark stripe on scale rows 2 and/or 3 posteriorly. In preserved specimens of all three species the details of color patterns can be difficult to discern. Viewing the pattern under alcohol in good light usually reveals the pale crossbands or ocelli in D. nuchale and D. percarinatum . Dendrophidion brunneum also has a rather rectangular loreal scale that is longer than tall, whereas the loreal in D. percarinatum and D. nuchale is an irregular polygon as tall as, or often taller than, it is long.

Description. Characteristics of Dendrophidion brunneum are summarized in Table 1 . Because tails are frequently broken, the maximum size was estimated from the individuals with greatest SVL. Linear regressions of tail length on SVL (see Materials and Methods) were: for males, log (tail length) = −0.413 + 1.104(log SVL); for females, log (tail length) = −0.616 + 1.163(log SVL). The five largest males were 542– 700 mm SVL, of which three had incomplete tails (all except the largest were ≤ 580 mm SVL). The estimated total length of the largest male (ANSP 31776) is 1235 mm (actual total length 879+ mm). The five largest females were 649–796 mm SVL but all of these had incomplete tails (three were> 700 mm SVL). The estimated total length of the largest female (FMNH 232676) is 1369 mm (actual total length 1114+ mm). These are larger than previous size records ( Lieb 1988, Kuch & Freire 1993).

The tail is 40–44% of total length (67–80% of SVL) in males, 38–41% of total length (61–71% of SVL) in females. Günther (1858: 116) reported measurements of the holotype as 12 inches tail length and 39 inches total length (tail = 31% of total length), which suggests an incomplete tail; Parker (1938: 443) confirmed that the type has a “mutilated tail” ( Boulenger [1894: 16] also reported the subcaudal number as “?”). Dorsal scales in 17–17–15 rows (rarely 17–17–13), with seven to nine median rows moderately keeled; weaker keels are often present on additional rows. Scale row reduction is by loss of dorsal row 3 (usually) or, less commonly, fusion of rows 3 + 4 or 2 + 3 at ventrals 86–106 (n = 11). Two apical pits are present on the dorsal scales of the neck and anterior body, and occasionally on other dorsal scales. Ventrals 145–152 (averaging 148.4) in males; 151–165 (averaging 158.3) in females. One to four preventrals precede the ventrals. Ventrals plus subcaudals 285–309 (n = 20). Anal plate divided. Subcaudals 139–158 (averaging 148.1) in males; 135– 149 (averaging 141.8) in females. Dorsocaudal scale reduction from eight to six at subcaudals 9–22 in males (n = 21), 4–10 in females (n = 19).

Loreal rectangular, usually 1.5× or more longer than tall; bordered by supralabials 2–3 or 2–4. Preoculars usually 1. Postoculars 2. Primary temporals usually 2 or 1, rarely 3; secondary temporals usually 2, rarely 1 or 3. Irregular divisions of the temporal scales are relatively common, forming small scales intercalated among the temporal series. Supralabials usually 9 with 4–6 bordering the eye, occasionally 8 (4–5) or 10 (4–6). Infralabials usually 10, rarely 9 or 11. Anterior gulars usually bordered by infralabials 1–5 (occasionally 6); posterior gulars usually bordered by infralabials 5–6 (occasionally 5–7). Maxillary teeth 30–38 (n = 17); at least two, and up to four of the posterior maxillary teeth are somewhat enlarged compared to more anterior teeth. Günther (1863: plate 6, fig. A;? holotype) illustrated dorsal and lateral head scales of D. brunneum (see also Fig. 1 ).

Samples were too small and geographically concentrated in northern Peru to detect patterns of geographic variation. The northernmost specimen examined (UMMZ 83706, a male from Imbabura Province, Ecuador) had the lowest dorsocaudal reduction (9) for males, but other characteristics of this specimen were typical. My data for segmental counts are comparable to those summarized by Lieb (1988: Table 1 ) except that Lieb reported lower bounds for ventrals and subcaudals of 143 and 130, respectively (Lieb’s tabulations were based on unpublished data of James A. Peters).

Sexual Dimorphism. Sexual size dimorphism is female-biased in Dendrophidion brunneum . Considering individuals> 400 mm SVL in the total sample, the mean body size of females (614.6 mm SVL; n = 16) is significantly greater (P <0.01) than the mean body size of males (533.1 mm SVL; n = 17); the largest specimen was also a female ( Table 1 ). Size at sexual maturity is not known for D. brunneum . However, in two other species that attain similar maximum SVLs, D. percarinatum and D. dendrophis , the smallest sexually mature males and females were 441–492 mm SVL ( Stafford 2003; Prudente et al. 2007). Females average about ten more ventral scutes than males (P <0.001), whereas males average 6.3 more subcaudals than females (P <0.01). Males have a somewhat greater mean relative tail length than females (42% vs. 40% of total length; 73% vs. 68% of SVL, respectively; P <0.001). The dorsocaudal reduction from eight to six occurs more distally in males (mean subcaudal 15.5) than in females (mean subcaudal 7.5) (P <0.001), probably due to the greater diameter of the tail base needed to accommodate the hemipenes and their retractor muscles.

Qualitatively, the patterns of sexual dimorphism in D. brunneum are the most frequent patterns in colubroids ( Shine 1993, 1994). However, other species of Dendrophidion show different patterns, at least in size dimorphism. No significant differences between mean adult male and female SVL were found for the Amazonian species, D. dendrophis ( Prudente et al. 2007) , nor for three Central American species ( D. nuchale , D. percarinatum , and D. vinitor ; Stafford 2003). Like D. brunneum , these other species also show only a small degree of sexual dimorphism in relative tail length. Sex differences in segmental counts were not analyzed by Stafford (2003) or Prudente et al. (2007). Tails in several species of Dendrophidion , including D. brunneum , are exceptionally long compared to other colubroids ( King 1989; Cadle 2009) but the small magnitude of the difference between male and female relative tail lengths ( Table 1 ) suggests a primary role for the long tails as an antipredator defense (see Natural History and Behavior).

Coloration in Life. In life, most specimens of Dendrophidion brunneum are medium green to greenish brown dorsally, often with yellowish or bronze highlights ( Fig. 1 ); less commonly, the dorsal color is predominantly brown or olive. Like other species of Dendrophidion , the anterior and posterior body are often somewhat different shades or colors, with gradual transition between colors (e.g., greenish anteriorly to more brownish posteriorly). The head and anterior part of the neck are usually a deeper green, greenish brown, or yellowish brown than the rest of the dorsum. The top of the head is often a contrasting color of deep green, blue green, or even bluish ( Fig. 1 ), with an abrupt transition to the neck color. The tip of the snout, supralabials, and infralabials are whitish to brown, with dusky to bluish or greenish pigment on the upper parts of the supralabials. Some specimens have fine copper-colored or yellow flecks on the anterior dorsal scales (under magnification appearing as narrow borders on the anterolateral edges of each scale); these flecks may extend for half or more of the body length but are most vivid anteriorly. Some specimens have black tips to scattered dorsal scales, generally more concentrated middorsally, but these are nowhere distinct. The skin between the anterior dorsal scales is blue-gray, dark gray, or blackish with small white spots; these colors may enhance a defensive display involving inflation of the neck (see Natural History and Behavior). The tongue is blackish. The venter is white to dirty whitish, sometimes with a pale yellow or pale green wash, and usually with dark blue-gray squarish markings laterally.

None of the color variations seem particularly associated with size or sex. Four juveniles (277–319 mm SVL) are colored similarly to adults (see detailed description for FMNH 232677 below). I did not observe distinct stripes or crossbands in live specimens but three preserved specimens have such patterns, as described below. The following are detailed color notes from life for several specimens:

FMNH 232676, female, 796 mm SVL. Dorsum greenish brown with occasional black-tipped scales on the median seven dorsal scale rows. Dorsal scales are yellowish brown for approximately 10 cm behind the head, with the anterior portions of some scales in this region bright yellow. Top of head and approximately five dorsal scale rows behind are deep green (almost blue-green); this color extends to upper edge of supralabials, below which the supralabials are white. Rostral and nasal scales brown. Iris brown. Infralabials white except for the last two, which are green. Gular region and anterior ventrals white; ventrals become dirty yellowish white and this continues onto subcaudals to the tail tip (which is incomplete). Lateral edges of ventrals greenish gray. A thin irregular black line borders the anterior edge of each ventral after the twentieth (this line is overlapped by the posterior edge of the preceding ventral, so as to appear gray). Subcaudals are patterned like the ventrals, but greenish gray pigment tends to border the anterior edge of each scale. Skin between scales on neck is dark gray and quite loose (i.e., expansible).

FMNH 232677, juvenile male, 319 mm SVL. Dorsum posterior to level of ventral 30 is uniform medium brown. Anterior to this the dorsum is greenish brown, becoming medium leaf green on lateral dorsal scales for approximately 3 cm behind the head. Dorsal surface of the head down to the dorsal edge of the supralabials is dark green. Lower part of supralabials white. Rostral brown. Iris brown. Lower labials and gular region white. Ventrals dirty white, bordered laterally by brown. Indistinct black line bordering anterior edge of each ventral posterior to heart. Subcaudals yellowish white, bordered laterally by brown. Skin between scales of the anterior body blue-gray.

MUSM-JECadle field number 7148 (sex and measurements not available). Dorsum olive green with coppery or brown pigment dorsally that is most intense on the median seven dorsal rows. The coppery sheen is produced not by a general coloring of the dorsum, but by each scale being green with coppery pigment on the posterior one-third. The coppery pigment is replaced by a more yellowish color for about 8–10 cm behind the head. Head medium dull green with brown pigment on parietals, supraoculars, and nasals (but covering only part of each scale). Belly cream colored; ventral surface of tail creamy white with medium green laterally. Upper and lower labials and gular region white.

LSUMZ 32560, female, 629 mm SVL. Olive green anteriorly to dark olive green posteriorly. Venter pale yellow (Field catalogue of Richard Thomas for RT 3108).

LSUMZ 32562, male, 470 mm SVL. Deep green anteriorly (head and neck) to dark olive green on posterior three-quarters of body and tail; venter white anteriorly to very pale green posteriorly and on underside of tail (Field catalogue of Richard Thomas for RT 3246).

Coloration of Preserved Specimens. Most preserved specimens of Dendrophidion brunneum are relatively uniform gray, grayish brown, dull green, olive, or even blackish (perhaps from overly strong formalin fixation). The stratum corneum is easily lost from the dorsal scales, with the resulting areas being more gray, blue-gray, or bluish than brown. Some specimens have scattered minute dark brown specks on the tips of some dorsal scales, usually on paravertebral rows and more prevalent on the posterior body than anteriorly.

Two males from Ecuador had indications of dorsolateral and lateral stripes. KU 142802 (Loja Province, Ecuador) was dull bluish green similar to other preserved specimens, but a continuous reddish brown streak occupied three paravertebral scale rows (dorsal rows 6–8 on each side on the anterior body) and extended from the head to the tail tip (the streaks from each side merging on the tail). In addition, a diffuse narrow reddish brown streak was present on each side, anteriorly on scale row three, dropping to scale row two on the anterior one-third of the body and continuing on row two to the vent. The lateral streaks are diffuse because they do not cover the entire scale row, appearing as a ‘blur’ of spots on the flank. USNM 237042 (Azuay Province, Ecuador) is dark gray overall but pale dorsolateral stripes are evident on dorsal rows 6–7 on each side (dropping to rows 5–6 posterior to the dorsal scale reduction) from about midbody to the proximal portion of the tail. A much less distinct lateral stripe is on dorsal row 2 on each side; it ends at the vent. The stripes in USNM 237042 are indicated by a general lightening of the central part of each scale in these rows, which becomes less distinct anterior to midbody.

Pale crossbands or anterior blotches are typical for most species of Dendrophidion ( Lieb 1988, Savage 2002: 654–658) but I recorded no specimens of D. brunneum in the field with such patterns. Nonetheless, faint pale crossbands one dorsal scale row or less in width and separated from one another by five dorsal rows, are discernible on the anterior body of FMNH 232578 (514 mm SVL) when the specimen is immersed in alcohol. Pale anterior crossbands are variably expressed in at least one other species of Dendrophidion , D. nuchale ( Savage 2002: 654) , and they occur commonly in several species. Given the prevalence of pale anterior crossbands in other species of Dendrophidion , their presence in occasional specimens of D. brunneum suggests expression of a pattern that is perhaps plesiomorphic for the genus.

Figures

FIGURE 1. Dendrophidion brunneum in life. Specimens are from the Río Zaña Study Site, Cajamarca Department, Peru. The contrasting head and body coloration and yellow highlights on neck scales (lower photo) are typical.

Tables

TABLE 1. Scale counts, measurements, and other data for specimens of Dendrophidion brunneum. Data are given for the population of the Río Zaña Study Site and for the entire sample. Body proportions and ventral and subcaudal counts are given as range followed by mean ± s. d. Bilateral counts are separated by a slash (/). For pre- and postoculars, temporals, and labial scales, each side of each specimen was counted as an independent observation. SVL = snout to vent length; measurements in millimeters. Sample sizes in parentheses.

	Río Zaña Study Site	Total Sample
Largest Specimens: Total Length (estimated), SVL	1235, 700 (3) 1369, 796 (Ƥ)	1235, 700 (3) 1369, 796 (Ƥ)
Tail Length /Total Length	0.42–0.44 (3) 0.43 ± 0.008 (6) 0.38–0.41 (Ƥ) 0.40 ± 0.012 (6)	0.40–0.44 (3) 0.42 ± 0.011 (11) 0.38–0.41 (Ƥ) 0.40 ± 0.012 (9)
Tail Length /SVL	0.71–0.80 (3) 0.75 ± 0.03 (6) 0.61–0.71 (Ƥ) 0.67 ± 0.04 (6)	0.67–0.80 (3) 0.73 ± 0.03 (11) 0.61–0.71 (Ƥ) 0.68 ± 0.03 (9)
Maxillary Teeth	30–35 (14)	30–38 (17)
Dorsal Scales	17–17–15 (29)	17–17–15 (39) 17–17–13 (1)
Ventrals	146–152 (3) 148.57 ± 1.99 (14) 155–165 (Ƥ) 159.54 ± 2.82 (13)	145–152 (3) 148.43 ± 2.20 (21) 151–165 (Ƥ) 158.33 ± 3.43 (18)
Subcaudals	147–158 (3) 150.83 ± 3.82 (6) 141–149 (Ƥ) 144.00 ± 3.74 (5)	139–158 (3) 148.09 ± 4.76 (11) 135–149 (Ƥ) 141.78 ± 4.32 (9)
Dorsocaudal reduction, 8 to 6 (subcaudal number)	12–22 (3) 4–10 (Ƥ)	9–22 (3) 4–10 (Ƥ)
Preoculars	1/1 (27) 1/2 (1)	1/1 (37) 1/2 (1)
Postoculars	2/2 (28)	2/2 (38)
Primary temporals	1 (11) 2 (45)	1 (16) 2 (59) 3 (1)
Secondary temporals	1 (1) 2 (53) 3 (2)	1 (1) 2 (73) 3 (3)
Supralabials, supralabials touching eye	8, 4–5 (2) 9, 4–6 (46) 10, 4–6 (6)	8, 4–5 (6) 9, 4–6 (61) 10, 4–6 (6)
Infralabials	9 (3) 10 (48) 11 (1)	9 (4) 10 (68) 11 (1)