Hydrodynastes melanogigas, Franco, Francisco L., Fernandes, Daniel S. & Bentim, Bruno M., 2007

Franco, Francisco L., Fernandes, Daniel S. & Bentim, Bruno M., 2007, A new species of Hydrodynastes Fitzinger, 1843 from central Brazil (Serpentes: Colubridae: Xenodontinae), Zootaxa 1613, pp. 57-65 : 58-62

Hydrodynastes melanogigas sp. nov.

Hydrodynastes gigas nec Duméril, Bibron & Duméril — Brandão, R. A. and Peres Jr., A.K. 2001. Levantamento da Herpetofauna na área de influência do aproveitamento hidroelétrico Luís Eduardo Magalhães, Palmas, TO. Humanitas, Revista de Divulgação Científica, Palmas, 3:35–50.

Hydrodynastes gigas nec Duméril, Bibron & Duméril — Puorto, G. and Barbarini, C. C. 2004. Coleção Herpetológica do Museu de Zoologia do Centro Universitário Luterano de Palmas – MZCEULP. Humanitas, Revista de Divulgação Científica, Palmas, 4/6:31–38.

Holotype: IBSP 65796 adult male, Municipality of Palmas (10o12’46’’S 48o21’37’’W, 230 m above sea level), State of Tocantins, Brazil; collected between 21–30 January 2002 by Marisa M.T. da Rocha, Myriam E.V. Calleffo, and Silvia R. Travaglia-Cardoso.

Paratypes: IBSP 65978 young male, collected on 26 January 2002, and IBSP 66387 adult male, collected between 21–30 January 2002, both Municipality of Porto Nacional (10o42’29’’S; 48o25’02’’W, 212 m above sea level), State of Tocantins, Brazil, by Marisa M.T. da Rocha, Myriam E.V. Calleffo, and Silvia R. Travaglia-Cardoso; IBSP 65380, 65383, 65385, and 65386, three adult males and one adult female, respectively, Municipality of Palmas collected between 07–12 January 2002 by Sávio S. Sant’Anna; MNRJ 15101 (formerly IBSP 65797), IBSP 65791-95, 66005, 66242, and 66595, six adult males, one young male, one young female, and one adult female, respectively, collected between 21–30 January 2002, Municipality of Palmas by Marisa M.T. da Rocha, Myriam E.V. Calleffo, and Silvia R. Travaglia-Cardoso; IBSP 65144 adult male, Municipality of Lajeado (09o45’05’’S; 48o21’29’’W, 202 m above sea level) collected between December 2001 and January 2002 by researchers of Instituto Butantan.

Diagnosis: the new species is distinguished from H. gigas and the two subspecies of H. bicinctus by having a general melanistic color pattern, with head and dorsum of the body mostly dark-brown to black; absence of postocular stripe; venter grayish-brown, with dark rounded blotches outlining two lateral stripes which become gradually paler towards the posterior region of the belly, disappearing after midbody. It is further distinguished from the two subspecies of H. bicinctus by having two apical pits, and 16–17 prediastemal teeth.

Comparisons with other species: the other two species of the genus have a creamish-brown general ground color, conspicuous black postocular stripe, and dorsum with saddle-like dark-brown or black blotches. Furthermore, the ground color of the venter is creamish-brown with regular lateral stripes (in H. gigas ) or with irregular rounded blotches (in H. bicinctus ) distributed along the venter. Hydrodynastes bicinctus has no apical pits and 11–13 prediastemal teeth. All three species show sexual dimorphism in ventral and subcaudal scales: H. melanogigas (F1.31 = 60.53; p <0.01; N = 33; and F1.22 = 230.94; p<0.01; N = 24, respectively); H. gigas (F1.143 = 60.68; p <0.01; N = 145; and F1.132 = 124.2; p <0.01; N = 134, respectively); H. bicinctus (U = 531; p <0.01; N = 91; and F1.74 = 54.46; p <0.01; N = 76, respectively). Refer to Table 1 for other comparisons with the species of Hydrodynastes .

H. melanogigas H. gigas H. bicinctus MxT x = 16.3; s = 0.52 x = 15.9; s = 0.83 x = 12.3; s = 0.6

r = 16–17+2; n = 6 r = 15–17+2; n = 8 r = 11–13+2; n = 26 SL 7 (1 side); 8 (63 sides); 7 (3 sides); 8 (277 sides); 9 (8 7 (5 sides); 8 (162 sides)

9 (2 sides) sides) 9 (15 sides)

r = 7–9; n = 33 r = 7–9; n = 144 r = 7–9; n = 91

IL 9 (5 sides); 10 (50 sides) 9 (1 side); 10 (116 sides); 11 (170 9 (1 side); 10 (119 sides)

11 (9 sides); 12 (2 sides) sides) 11 (60 sides)

r = 9–12 12 (1 side); r = 9–12 r = 9–11

n = 33 n = 144 n = 90

AP present present absent

Description of the holotype ( Fig. 1–4 ): adult male, SVL 1315 mm; TL 480 mm (36.5% SVL); head length 51 mm (3.9% SVL) from tip of snout to quadrate articulation; broadest head width 29.2; interocular distance 20.2 mm; snout-orbit distance 15.2 mm (0.75 time interocular distance); cervical constriction poorly evident and body robust, round in transversal section; dorsum of the head and anterior portion of body with dermal papillae; rostral 1.4 times as broad as high, visible from above; two internasals as broad as high; prefrontals 1.1 time as long as broad; frontal 1.4 times as long as broad, pentagon-shaped in dorsal view; parietals 1.6 times as long as wide; nasals divided (prenasals wider than postnasals); loreal trapezoid-shaped, 1.6 times as long as high; eye diameter 6.9 mm; pupil round; three suboculars, the third larger than the others; one supraocular and two postoculars; temporals 3+2+3/2+2+3, upper secondary temporal fused to the upper tertiary on the left side; upper tertiary temporal considerably larger than the others extending beyond parietals; eight supralabials none contacting the eye; three suboculars (posterior larger than the others) between eye and supralabials; symphisial separated from chin shields by the first pair of infralabials forming a median suture; ten infralabials, the first six contacting the chin shields; two pairs of chin shields, anterior slightly larger than posterior; five gular scale rows between the first ventral and the infralabials; 17 prediastemal maxillary teeth; dorsal scales in 19-19-15 rows, smooth with two apical pits; two pre-ventrals; 167 ventrals; cloacal plate single; 83 paired unkeeled subcaudals.

Color pattern of holotype in preservative (ethanol 70%): dorsal part of head black except for the rostral, prefrontals, loreal, and nasals shields which are mostly dark-brown; frontal and parietals black, with a few scattered dark-brown blotches; dorsum with some scales grayish-brown on a mostly black background; first five supralabials mostly creamish-white with dorsal edges and suture portion black; last three supralabials roughly black; first seven infralabials creamish-white with black suture lines; chin shields mostly creamish-white; gular scales creamish-white with scattered black blotches; venter grayish-brown; lateral edges of ventrals with dark rounded blotches outlining two lateral stripes which become gradually paler towards the posterior region of the belly, disappearing after midbody; a third central stripe is conspicuous only at the level of the first ventrals.

Hemipenis (everted organ; Fig. 5–6 ): deeply bilobed, semicalyculate, semicapitate, with about 50 enlarged spines arranged in 3 to 4 rows on each lateral side of the hemipenial body; sulcus spermaticus bifurcates on the proximal region of organ; branches with centrolineal orientation until the level of the calyculate region, diverging to a centrifugal position terminating on the distal lateral region of each lobe; capitation stronger on the asulcate side which shows conspicuous calyces that delineate a discrete groove characterizing semicapitation; capitulum with papillate calyces, more conspicuous and enlarged on the inner lateral regions of hemipenis; body calyces poorly developed on basal and central regions of hemipenial body, being more evident in the lobes on the asulcate side, where they delimit a papillate crest between the lobes on the apical portion of hemipenial body; hemipenial body covered with spinules; basal portion of sulcate side with a larger density of spinules, which are enlarged when compared to the rest of hemipenial body.

Variation (paratypes and additional specimens): largest male ( IBSP 65383) SVL 1475 mm, TL 543 mm; largest female ( IBSP 66595) SVL 1600 mm (tail incomplete); tail 29.8–38.3% of SVL in males and 24.6–34.1% of SVL in females; preoculars 1/1 (N = 31) or 2/1 (N = 1); postoculars 2/2 (N = 31) or 3/3 (N = 1); temporal formula variable, but frequently 2+2+3/2+2+3 (N = 16) or 2+1+2/2+2+3 (N = 5); supralabials 8/ 8 (N = 30), 8/9 (N = 2) or 7/8 (N = 1); infralabials 10/10 (N = 18), 11/10 (N = 7), 10/9 (N = 5), 12/10 (N = 2), 11/11 (N = 1); dorsal scales in 19–19–15 (N = 31) or 19–17–15 (N = 2) rows; prediastemal maxillary teeth 16–17 (x = 16.3; s = 0.52; N = 6); ventrals 160–170 (x = 163.7; s = 2.73; N = 19) for males and 167–173 (x = 170.14; s = 1.66; N = 14) for females; subcaudals 80–86 (x = 83.1; s = 1.85; N = 15) for males and 71–74 (x = 72.6; s = 1.24; N = 9) for females. Some specimens present a color pattern with vestiges of dorsal saddlelike dark-brown blotches in some portion of the body. Gular region immaculate or with black blotches, and lateral stripes of the venter may become indistinct on the first or last third of the belly.

Distribution ( Fig. 7 ): specimens of H. melanogigas are known from the municipalities of Lajeado, Palmas, and Porto Nacional, State of Tocantins, central Brazil. These localities are situated in the margins of the Tocantins River. The predominant vegetation is the Cerrado, although elements of Amazonian fauna may reach this region through the gallery forests of this river and its tributaries ( Eiten, 1972).

Etymology: the specific epithet is a composite name from the Greek melas (black) + gigas (giant).

Figures

FIGURE 7. Distribution of the examined specimens of Hydrodynastes. Hydrodynastes melanogigas (triangles); H. gigas (circles); and H. bicinctus (squares).

FIGURE 1 – 4. Holotype of Hydrodynastes melanogigas (IBSP 65796). 1, dorsal; 2, ventral view; 3, lateral of the head; 4, dorsum of the head.

FIGURE 5 – 6. Hemipenis of Hydrodynastes melanogigas (IBSP 65383). 5, sulcate; 6, asulcate side. Scale bar 5 mm.

Tables

TABLE 1. Data for all examined specimens of Hydrodynastes. VE = number of ventrals; SC = number of subcaudals; MxT = number of maxillary teeth; SL = number of supralabials; IL = number of infralabials; AP = apical pits; x = mean; s = standard deviation; r = range; n = sample size.

	males	females	males	females	males	females
VE	x = 163.7 s = 2.73 r =160–170 n = 19	x = 170.1 s = 1.66 r = 167–173 n = 13	x = 156.2 s = 3.7 r = 148–166 n = 66	x = 161.7 s = 4.63 r = 152–179 n = 79	x = 168.9 s =2.78 r = 163–175 n = 56	x = 172.3 s = 4.42 r = 164–180 n = 35
SC	x = 83.1 s = 1.85 r = 80–86 n = 15	x = 72.6 s = 1.24 r = 71–74 n = 9	x = 80.3 s = 5.7 r = 59–88 n = 61	x = 69.7 s = 5.25 r = 51–78 n = 73	x = 81.2 s = 4.3 r = 69–93 n = 49	x = 73.0 s = 5.2 r = 60–81 n = 27