Dipsas albifrons ( Sauvage, 1884 )

Passos, Paulo, Fernandes, Ronaldo & Porto, Marcovan, 2005, Geographical variation and taxonomy of the snail-eating snake Dipsas albifrons (Sauvage, 1884), with comments on the systematic status of Dipsas albifrons cavalheiroi Hoge, 1950 (Serpentes: Colubridae: Dipsadinae), Zootaxa 1013 (1), pp. 19-34 : 26-30

Dipsas albifrons ( Sauvage, 1884) ( Fig. 5 )

Dipsadomorus albifrons Sauvage, 1884

Leptognathus albifrons — Boulenger, 1896

Dipsas albifrons — Mocquard, 1908

Cochliophagus albifrons — Ihering, 1911

Dipsas albifrons — Amaral, 1923

Dipsas albifrons albifrons — Hoge, 1950

Dipsas albifrons cavalheiroi Hoge, 1950

Dipsas albifrons — Peters, 1960

Lectotype: Instituto Butantan IBSP 17746 (previously Muséum National d'Histoire Naturelle de Paris MNHN 6106 ), adult female, SVL 390 mm, TL 139 mm, collected by Ferry from Brazil [designated herein].

Paralectotype: Muséum National d'Histoire Naturelle de Paris MNHN 6293 , adult female, collected by Ferry from Brazil [designated herein] .

Diagnosis: Distinguished from all congeners by the combination of 15 dorsal scales rows; vertebral scale row not or slightly enlarged; maxillary teeth 11–15; pterigoyd short, toothless, not curved and lacking the quadrate process; hemipenis single; and dorsal pattern of irregular blotches extending less than half of length of interspaces.

Comparisons: Species groups of Dipsas were diagnosed manly by color pattern by Peters (1960). The Dipsas variegata group is distinguished from the other groups by a dorsal ground color generally light with dark, narrow (usually higher than long), irregular, lateral blotches not as wide as interspaces over the greater part of the body. The interspaces in this group are rarely unicolored and frequently marked with streaks, spots, and stippling throughout the body.

Dipsas albifrons can be distinguished from others species of the D. variegata group by a suite of diagnostic features. It may be distinguished from D. andiana , D. incerta , D. neivai , D. nicholsi , and D. variegata by lacking pterigoydal teeth; from D. alternans , D. variegata , D. andina , and D. nicholsi by having a pair of parallel dark brown spots on the head that are not connected anteriorly (instead of conspicuous white bordered dorsal ocelli in D. alternans , irregular blotches in D. variegata and a n­shaped black marking on D. andina and D. nicholsi ); from D. neivai , D. andina , D. nicholsi , and D. variegata by having a single hemipenis (instead of a deeply bilobed in the first or slightly bilobed in the others); from D. andiana , D. nicholsi , and D. incerta by a lower number of ventral and subcaudal scales (see Cadle & Myers 2003 and Passos et al. 2004, respectively); from D. alternans and D. nicholsi by possessing a conspicuous series of small diamond shaped dots in the mid portion of interspaces.

Description of lectotype ( Fig. 5 ): Head distinct from body, head length 15.3 mm (3.9% of SVL) from rostral scale to posterior tip of mandibles, head width 8.4 mm (55.3% of head length) at broadest point; interocular distance 4.9 mm; snout­orbit distance 2.7 mm (0.60 times interocular distance); rostral twice broader than high, visible from above; internasals and prefrontals slightly broader than long, the former about 0.75 times longer than the latter; prefrontals not entering orbit; frontal as broad as long; parietals about 0.75 times longer than wide; nasal divided on right side and semi­divided on left; one preocular; loreal higher than long entering orbit; distance across eyes 3.25 mm; one postocular; temporal formula 1+2; seven supralabials, third to fifth entering orbit; symphysial broader than long; eleven infralabials on left and twelve infralabials on right side, two pairs in contact behind symphysial, second to fifth on left and third to fifth on right side contacting first pair of genials, fifth to seventh on left and fifth to eighth on right side contacting second pair of genials; three pairs of genials; 15 dorsal scales rows along entire body, dorsal scales smooth; vertebral row scarcely enlarged; seven dorsal scales rows on tail, at level of second subcaudal; 177 ventrals; anal plate entire; 83/84 subcaudals. Thirteen maxillary and six palatine teeth; pterygoid toothless. Coloration is mostly faded, blotches two scales long in anterior and posterior regions, and three scales long at midbody; interspaces about six scales long along body.

Color in preservative: The color pattern of preserved specimens is compatible with that of the lectotype. Dorsum of head uniformly light brown except for faded dot over frontal and two parallel dark­brown spots over parietals, often diverging posteriorly; supralabials light­brown, almost creamish white along ventral edge; infralabials and gular region uniformly creamish white; dorsal ground color of body beige; dorsum of body with 17–32 (= 23.04; SD = 2.37; N = 122) well­defined, nearly elliptical, dark­brown, white bordered dorsal blotches; blotches smaller than interspaces along body, generally with 3/2/ 2 scales long; blotches eventually join in vertebral region and extend to paraventral area; interspaces generally six scales long; venter generally with anterior portion light­brown, posteriorly becoming brown under tail, irregular streaks arising on mid and/or posterior portion of venter to tail; streaks of different tones and size, sometimes forming irregular dots between interspaces in paravertebral region; tail with 11–19 (= 15.27; SD = 1.64; N = 39) blotches in males and 11–18 (= 13.76; SD = 1.63; N = 71) in females, with same pattern as body.

Hemipenis ( Fig. 6 ) [everted organ N = 7]: Organ single, cylindrical, with bulbous shape, slightly larger at apices; strongly capitate; capitulum completely encircles organ and occupies more than distal half of hemipenial body on sulcate side; capitulum occupies less than distal half of hemipenial body on asulcate side; capitulum ornamented with high number of papillate calyces, more concentrated on the sulcate side; sulcus spermaticus divides approximately on most basal region of capitulum; branches in centrolineal orientation terminating almost at distal region of capitulum; basal portion of hemipenial body with large spines (ca. 30) arranged in several rows and concentrated on portion adjacent to capitulum; some spines on lateral region; both sides with spinules among large spines, despite being more concentrated on sulcate side.

Hemipenis variation: The organ extends (in situ) to the level of the 5–10th (= 8.07; SD = 1.23; N = 34) subcaudal; the musculus retractor penis magnus originates between the 20–26th subcaudal. In northern populations, the papillate calyces are less conspicuous in both sides.

Meristic variation: Largest male 559 mm SVL, 215 mm TL; largest female 690 mm SVL, 227 mm TL. Ventrals 154–191 (= 169.88; SD = 7.46; N = 90) in females, 159– 187 (= 172.87; SD = 6.08; N = 49) in males; subcaudals 70–96 (= 80.08; SD = 5.03; N = 81) in females, 68–97 (= 85.62; SD = 5.26; N = 42) in males; preoculars 1 (N = 158 sides), 2 (N = 4 sides) or none (N = 116 sides); supralabials 6–10 (= 7.81; SD = 0.63; N = 139), supralabials touching the orbit 3–4 (N = 7), 3–5 (N = 23), 3–6 (N = 4), 4–5 (N = 71), 4–6 (N = 27), 5–6 (N = 7); infralabials 8–13 (= 10.85; SD = 0.71; N = 138), 1–4 (= 2.34; SD = 0.62; N = 136) pairs in contact behind symphysial and generally 3­6 touching first pair of genials and 5­8 touching second pair of genials; nasal divided (N = 53) or semidivided (N = 31); 1 postoculars (N = 13 sides), 2 postoculars (N = 164 sides); temporals 1+1 (N = 3), 1+2 (N =116), 2+1 (N = 4), 2+2 (N = 13), 2+3 (N = 3); maxillary teeth 11–15 (= 13,71; SD = 0.82; N = 75); palatine teeth 6–9 (= 7.38; SD = 0.76; N = 13); dentary teeth 20–25 (= 22.63; SD = 1.56; N = 11).

Distribution ( Fig. 1 ): Dipsas albifrons occurs in southeastern and southern Brazil, from the states of Espírito Santo to Santa Catarina with a large gap along the continental portion of the State of São Paulo.

Figures

FIGURE 1. Geographical distribution of Dipsas albifrons, showing the three morphometric groups.

FIGURE 5. Dorsal (A) and lateral (B) views of the head of Dipsas albifrons (Sauvage, 1884) (IBSP 17746, lectotype). (Ruler equals to 5 mm).

FIGURE 6. Sulcate (A) and asulcate (B) sides of hemipenes of Dipsas albifrons. (A, from municipality of Corupá (IBSP 64929), State of Santa Catarina, Brazil (Ruler equals to 5 mm).