Xenoxybelis boulengeri ( Procter, 1923 )

Prudente, Ana Lúcia Da Costa, Silva, Márcio André Amorim Da, Rocha, Wáldima Alves Da & Franco, Francisco Luís, 2008, Morphological variation in Xenoxybelis boulengeri (Procter, 1923) (Serpentes, Xenodontinae, Philodryadini), Zootaxa 1743, pp. 53-61 : 54-55

Xenoxybelis boulengeri ( Procter, 1923)

Oxybelis boulengeri: Procter, 1923: 1062 . Type Locality: Rio Mamoré, Trinidad, Bolívia. Oxybelis argenteus: Amaral, 1930: 45 .

Oxybelis boulengeri: Keiser, 1989: 764 .

Xenoxybelis boulengeri: Machado, 1993: 99 .

Revised diagnosis. Xenoxybelis boulengeri is distinguished from X. argenteus by: loreal present (vs. absent); divided cloacal plate (vs. single); absence of dark spots on ventral side of head (vs. presence); presence of wide dark green band on median side of vent (vs. absence); presence of median dark green band on subcaudals (vs. absence); dark green dorsum (vs. dorsum with dark vertebral band); moderately long hemipenes, three times longer than wide (vs. string-like, about two times longer than wide); profoundly bilobed (vs. slightly bilobed), with two to four rows of lateral spines on each side, that extend from the sulcate to asulcate site, without any distinct rows larger than others (vs. two to four rows of lateral spines on each side, with one row larger than others).

Description. Smooth dorsal scales most frequently in 17/17/15 rows (n = 18), ranging from 17/17/13 (n = 1) to 15/17/13 (n = 1), without apical pits. Ventrals: 189–202 (n = 10) in males; 190–207 (n = 6) in females. Subcaudals divided: 174–198 (n = 10) in males; 180–209 (n = 6) in females. Divided cloacal plate. Cloacal glands of males and females reach the 4th and 5th subcaudals, respectively. Snout-vent length ranging from 561–721mm (x = 632.4; SD = 55.1; n = 10) in males; 592–790mm (x = 695.5; SD = 78.0; n = 7) in females. Tail length ranging from 330–472mm (x = 410.5; SD = 62.6; n = 10) in males; 424–508mm (x = 467.1; SD = 40; n = 7) in females. Elongate head, distinctly wider than neck, head length ranging from 20.3–25.2mm (x = 22; SD = 1.6; n= 9) in males; 24.7–30,0mm (x = 26.2; SD = 2.2; n = 7) in females. Distance from the eye to anterior of rostral plate ranging from 6.7–8.3mm (x = 7.43; SD = 0.57; n = 9) in males; 8.3–10.3mm (x = 8.8; SD = 0.76; n = 7) in females. Head width ranging from 6.6–7.9mm (x = 7.2; SD = 0.5; n = 7) in males; 8.2– 9,23mm (x = 8.7; SD = 0.6; n = 7) in females. Head height ranging from 5.6–7.6mm (x = 6.6; SD = 0.61; n = 7) in males; 6.5–9.2mm (x = 7.9; SD = 0.9; n = 7) in females. Eye width corresponding, on average, to 15.5% of the head length and eye height on average about 42.5% of the head height. One preocular, three postoculars. Temporals 1+2. Six supralabials, fourth larger than others and in contact with eye (n = 19). Eight infralabials (n = 15), rarely seven (n = 4). Two pairs of chin shields, posterior pair larger than anterior pair. Nasal single. Loreal longer than high. Rostral wider than high. Pentagonal frontal longer than wide, length on average about 24.6% of the head length.

Color pattern in 70% alcohol ( Fig. 1 ). Dorsal side of the body and head ranging from olive-green to brown. Lateral dark brown band begins on rostral area and extends along body as far as cloacal plate. This lateral band divides the dorsal coloration into two stripes: a dark green vertebral stripe and pale green lateral one. Pale green supralabials. Pale green ventral side of the head, without spots. Ventrals pale cream, with a wide median dark green band, beginning on first ventral and extending as far as end of the tail. Discrete, narrow, pale cream line in center of green band, begining on first ventral and extending as far as the vent, absent on subcaudals.

Hemipenis morphology ( Fig. 2 ). MPEG 18226, right organ removed for illustration. Organ bilobed, semicalyculate and semicapitate, about three times longer than wide at the level of the sulcus spermaticus division. Slightly divergent lobes, about 20% of the total length. On the sulcate side, there is a deep capitular sulcus delimitating the capitula, which is equal to about two-thirds of hemipenis size. Both capitula are almost totally confluent in broad intrasulcar region, forming an uninterrupted calyculate area restricted to sulcate side of the organ. Calyculate area occupying two-thirds of the sulcate side of organ. The sulcus spermaticus divides at the base of the capitulum, with centrolineal branches terminating on distal tip of lobes. The basal third of organ, on the sulcate side, with large lateral spines arranged in two to four longitudinal lateral rows. Lateral spines hook-like, decreasing in size toward apical region, being slightly larger in central area of the organ. Lateral spines increasing in size from sulcate to asulcate side, lacking row or rows of spines conspicuously larger than the others. Asulcate surface ornamented with two longitudinal and six parallel rows of papillate body calyces extending from the tip of the lobes to the base of the hemipenial body. Papillate crest runs on middle of asulcate surface between two rows of body calyces, covered with longitudinal row of small spines.

Geographic distribution ( Fig. 3 ). Xenoxybelis boulengeri occurs in Amazon Forest, from southeast Peru and northeast Bolivia to northern Brazil, in the states of Amazonas, Acre and Rondônia ( Procter, 1923; Cunha & Nascimento, 1978; 1993; Keiser, 1989; Machado, 1993).

Figures

FIGURE 1. Color pattern of Xenoxybelis boulengeri (MPEG 19537, Careiro da Várzea, Amazonas, Brazil). Lateral (A) and ventral (B) views of the head; lateral (C) and ventral (D) views of the body. Scale bar 20 mm

FIGURE 2. Hemipenes of Xenoxybelis boulengeri (MPEG 18226). Sulcate (A) and asulcate (B) views. Scale bar 5 mm.

FIGURE 3. Distribution of Xenoxybelis boulengeri (closed square – material examined; open square – literature records; closed triangle – type locality). Materials examined are listed in the Appendix.