Atractus tamessari, Kok, Philippe J. R., 2006

Kok, Philippe J. R., 2006, A new snake of the genus Atractus Wagler, 1828 (Reptilia: Squamata: Colubridae) from Kaieteur National Park, Guyana, northeastern South America, Zootaxa 1378, pp. 19-35 : 20-25

publication ID	https://doi.org/ 10.5281/zenodo.175024
DOI	https://doi.org/10.5281/zenodo.5693696
persistent identifier	https://treatment.plazi.org/id/03E2002D-FF87-FFD6-9537-A29A74E1AE5E
treatment provided by	Plazi
scientific name	Atractus tamessari
status	sp. nov.

Treatment

Atractus tamessari sp. nov.

Figs 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4

Holotype. IRSNB 2640 (field n° PK 1365), an adult male, collected along a tributary of Elinkwa River, ESE Kaieteur National Park, ca. 500 m elevation, Potaro-Siparuni District, Guyana (5°08’09”N, 59°25’28”W), on 23 March 2006 by P. J. R. Kok, Paul Benjamin and Giuliano Seegobin.

Paratypes. IRSNB 2641 (field n° PK 1372), a subadult female collected on 24 March 2006, same data as the holotype. IRSNB 2642 (field n° PK 1550), an adult female collected at the same locality as the holotype, in May 2006 by G. Seegobin.

Etymology. The specific name is a noun in the genitive case, honoring Michael Tamessar, retired Senior Scientific Officer of the Department of Biology at the University of Guyana (UG). Mike Tamessar spent most of his life encouraging Guyanese students to pursue studies in the fields of ichthyology and herpetology. Mike also collected many of the amphibians and reptiles in the collection of the Centre for Study of the Biological Diversity (CSBD) at UG.

Diagnosis. An Atractus species with 15 dorsal scale rows that can be distinguished from all other congeners by the following combination of characters: (1) medium size, adults reaching about 400 mm in TTL; (2) loreal much longer than high and touching the eye; (3) two postoculars; (4) eight supralabials, fourth and fifth touching the eye; (5) seven to eight infralabials, four in contact with chinshield; (6) six maxillary teeth; (7) 153–163 ventrals; (8) 28–31 subcaudals; (9) dorsal color pattern of irregular red or pale red markings, sometimes forming an incomplete broken dorsolateral stripe, on a medium brown to brownish black ground color; (10) venter yellowish cream, heavily mottled with brownish black.

The new species can be referred to the genus Atractus because it possesses the following combination of characters: medium size; head small, slightly distinct from neck; eye small, with semi-elliptical pupil; scales smooth; dorsal scales in 15 rows without reduction; loreal present, touching the eye and separating prefrontals and supralabials; nostril between two scales; single pair of chinshields; anal single; subcaudals divided; maxillary teeth decreasing in size posteriorly; occurring in northern South America ( Boulenger 1894, Hoogmoed 1980).

By having 15 dorsal scale rows at midbody, Atractus tamessari differs from all Atractus species having 17 scale rows in the Guiana Shield ( Silva Haad 2004, Avila-Pires 2005): A. alphonsehogei Cunha & Nascimento 1983, A. badius ( Boie 1827) , A. charitoae Silva Haad 2004 , A. duidensis Roze 1961 , A. favae ( Filippi 1840) , A. flammigerus ( Boie 1827) , A. latifrons ( Günther 1868) , A. lucilae Silva Haad 2004 , A. major Boulenger 1894 , A. riveroi Roze 1961 , A. schach ( Boie 1827) , A. snethlageae Cunha & Nascimento 1983, A. steyermarki Roze 1958 , A. torquatus Duméril, Bibron & Duméril 1854 , and A. zidoki Gasc & Rodrigues 1979 . Among the few Atractus species with 15 dorsal scale rows found in the region, Atractus tamessari differs from A. elaps ( Günther 1858) by having two postoculars (one in A. elaps ), eight supralabials (six), and no red or yellow rings on body (present); from A. franciscopaivai Silva Haad 2004 by having eight supralabials, three contacting the loreal (five supralabials, two contacting the loreal in A. franciscopaivai ), seven to eight infralabials (five), two postoculars (one), 1+2 temporals (1+1), and a yellowish cream venter heavily mottled with brownish black blotches (banded black and orange or black and yellow); from A. heliobelluomini Silva Haad 2004 by having eight supralabials, three contacting the loreal (seven supralabials, two contacting the loreal in A. heliobelluomini ), two postoculars (one), 1+2 temporals (1+1), and a yellowish cream venter heavily mottled with brownish black blotches (immaculate cream); from A. insipidus Roze 1961 by having eight supralabials, three contacting the loreal (seven supralabials, two contacting the loreal in A. insipidus ), and a yellowish cream venter heavily mottled with brownish black blotches (immaculate cream); from A. poeppigi ( Jan 1862) by having eight supralabials (six in A. poeppigi ), 1+2 temporals (0+1 or 0+2), the loreal much longer than high (slightly higher than long), and a yellowish cream venter heavily mottled with brownish black blotches (reddish cream or red and black); and from A. trilineatus Wagler 1828 by having 28–31 subcaudal scales (11–19 in A. trilineatus ), a yellowish cream venter heavily mottled with brownish black blotches (cream with light brown spots on posteriormost ventrals and anal), and by lacking well-defined longitudinal stripes (3–4 well-defined stripes present).

Description of the holotype. An adult male, TTL 397 mm, SVL 346 mm, TL 51 mm (12.8% of TTL); head slightly distinct from neck, length 1.4 times width (HW: 7.6 mm; HL: 10.8 mm); snout length (from eye to tip of snout) 4.0 mm, snout rounded in dorsal and lateral view; eye small (1.6 mm); pupil semi-elliptical; eye-nostril distance 29% of HL; rostral small, visible in dorsal view, width about 1.8 times height; internasals small, as long as wide, laterally in contact with anterior and posterior nasals; prefrontals large, length 1.4 times width, much larger than the internasals, irregularly hexagonal, touching eye, their medial suture asymmetrical, noticeably dextral to the medial internasal suture; frontal pentagonal, slightly wider than long, 1.1 times length of medial prefrontal suture; parietals large, length 1.5 times width, medial suture of parietals 1.2 times length of frontal. Nasal divided, posterior nasal as long as anterior nasal; preocular absent; loreal long, length 2.8 times height; postoculars 2/2, small, upper slightly larger than lower; temporals 1+2, lower posterior temporal slightly longer than upper; supralabials 8/8, eighth largest, first contacting nasals, second contacting posterior nasal and loreal, third and fourth contacting loreal, fourth and fifth touching eye, sixth contacting postocular and anterior temporal, seventh contacting anterior and posterior temporals, eighth contacting posterior temporal; infralabials 8/8, first four in contact with chinshields, first pair meeting at ventral midline, separating mental from chinshields; one pair of chinshields, length 2.5 times width ( Fig. 1 View FIGURE 1 ). Maxillary teeth 6; dorsal scales in 15-15-15 rows, smooth without apical pits; ventrals 153; anal single; paired subcaudals 31.

Color of holotype in life. The dorsal ground color is brownish black with numerous irregular bright red and paler red markings. The tail is brownish black with a few bright red lateral markings. The top of the head is brownish black. The snout is lighter, with a slight yellow wash. The supralabials are mostly yellow with the upper third dark brown, except for the eighth, which is almost completely dark brown with a small yellow spot anteriorly, and the first and the second, which are speckled with dark brown. The infralabials are mostly yellow with the lower third and posterior portion of each scale dark brown. The chinshields are mostly yellow with dark brown anteriorly and laterally. The mental groove area has a few dark brown speckles. The venter is yellowish cream with many irregular brownish black blotches, fewer blotches anteriorly, heavily mottled posteriorly. Underside of tail is brownish black with a few small irregular yellowish cream markings. The iris is brown ( Fig. 2 View FIGURE 2 ).

Color of holotype in preservative. After one month in preservative (70% ethanol after formalin), the red markings have faded slightly but are still well visible. The yellow coloration became white. The dark markings are unchanged.

Hemipenis. Almost fully everted right hemipenis about 10.5 mm long, extending to level of seventh subcaudal when adpressed to the tail; hemipenis differentiated (sensu Savage 1960), capitate, slightly bilobed, shallowly forked; lobes distinct from the base, each lobe nearly flattened on apical portion, displaying series of spinulate calyces; capitation stronger on asulcate side; sulcus spermaticus centrifugal, bifurcate, dividing about half of organ, at the base of apex; basal portion of hemipenial body covered by large spines ( Fig. 3 View FIGURE 3 ).

Variation. The type series consists of the male holotype and two female paratopotypes. The paratopotypes strongly resemble the holotype with the following exceptions (those of holotype in parentheses): TTL from 368–430 mm; SVL from 332–386 mm; TL from 36–44 mm, 9.8–10.2% of TTL (12.8%); HL from 10.6–11.5 mm; HW from 7.5–8.3 mm; 28–29 subcaudals (31); 157–163 ventrals (153); upper postocular 1.8 times the lower one in IRSNB 2641 (only slightly larger in the holotype and in IRSNB 2642); seven infralabials in IRSNB 2642 (eight in the holotype and in IRSNB 2641), apparently due to the fusion of infralabials 5 and 6. The sexual dimorphism in the number of ventrals and subcaudals is typical for this genus (Savage 1960). Prefrontal and internasal medial sutures are asymmetrical in both sexes (see Hoogmoed & Prudente 2003 and Myers 2003 for further discussion). The most striking difference between the paratopotypes and the holotype occurs in dorsal pattern and coloration, which is fairly variable. IRSNB 2641 has a medium brown dorsum with irregular pale reddish brown markings and two ventrolateral black stripes (instead of irregular bright red markings on a brownish black ground without ventrolateral stripes in the holotype and IRSNB 2642). In IRSNB 2642 the bright red markings form an incomplete broken dorsolateral stripe. The head of each paratype is medium brown and, as in the holotype, the snout is lighter with a yellow wash. The pale reddish brown markings on the dorsum of IRSNB 2641 disappeared in preservative, resulting in a uniform medium brown dorsum. Ventral patterns are similar, those of the male holotype slightly more mottled than the female paratopotypes ( Fig. 4 View FIGURE 4 ).

Distribution and ecology. Atractus tamessari is known only from the type locality ( Fig. 5 View FIGURE 5 ), which is located in the southeastern part of Kaieteur National Park, at the eastern edge of the Pakaraima Mountains ( Fig. 6 View FIGURE 6 ). The holotype and IRSNB 2641 were collected at night (ca. 22:30 h), crawling on the ground a few meters from a stream, almost exactly at the same place and the same time, at a 24h interval. IRSNB 2642 was collected by day, apparently sleeping, on a stump in the river. The habitat can be characterized as a submontane forest of the Pakaraima uplands on white sands dominated by clump wallaba ( Dicymbe spp) (ter Steege 2001). Examination of stomachs revealed no identifiable remains of prey, although X-rays of the male body showed the presence of sand in the digestive tract, which may suggest the recent ingestion of an earthworm, a very common food of Atractus ( Martins & Oliveira 1993, “ 1998 ” [1999]). No enlarged follicles were found in IRSNB 2641 ovaries; one egg was found in the abdominal cavity of IRSNB 2642, but as the specimen was cut in two by the collector, it is highly probable that other eggs were lost. All specimens have abdominal fat deposits. Other snake species collected in the immediate vicinity are the colubrids Chironius fuscus , Erythrolamprus aesculapii , Dipsas catesbyi , Dipsas cf. pakaraima , Helicops angulatus , Pseudoboa coronata , and the viperid Bothrops brazili .