Atractus paulus, Melo-Sampaio & Venegas, 2023

Melo-Sampaio, Paulo R. & Venegas, Pablo J., 2023, A new species of groundsnake genus Atractus Wagler, 1828 (Serpentes, Dipsadidae) from the Peruvian Andes revealed by unequivocal morphological characters, Evolutionary Systematics 7 (2), pp. 257-266 : 257

Atractus paulus sp. nov.

Figs 1 , 2 , 3

Atractus gigas non Myers & Schargel, 2006; Passos et al. 2010: 74. Melo-Sampaio et al. 2021a: 747; Appendix 1.

Type material.

Holotype. CORBIDI 877 adult female from Peru, Cajamarca Department: San Ignacio Province, Namballe District, Alto Ihuamaca (05°11'41.16"S, 79°05'2.27"W, 1641 m), collected by Maik Dobiey on 26 August 2008.

Paratype. ZFMK 89147 juvenile from Peru, Cajamarca Department, San Ignacio Province, Namballe District, El Chaupe (05°14'8.88"S, 79°06'16.2"W, 2161 m), collected by Maik Dobiey on 25 August 2008.

Diagnosis.

Atractus paulus can be distinguished from all congeners by the following combination of characters: (1) smooth dorsal scale rows 17/17/17 with apical pits near cloaca; (2) postoculars two; (3) loreal moderately long, contacting second to fourth supralabials; (4) temporal formula usually 1+2; (5) supralabials eight, fourth and fifth contacting eye; (6) infralabials eight, first four contacting chinshields; (7) maxillary teeth eight; (8) gular scale rows usually four; (9) preventrals four; (10) ventrals 166-167 in females, condition in males unknown; (11) subcaudals 26 in females, condition in males unknown; (12) in preservative, dorsum yellow ochre; (13) ventral surface of body mostly black with scattered inconspicuous cream marks in juveniles, uniform brown in adults; (14) maximum body size 830 mm SVL in females; (15) tail size moderately short in females (9.1-13.6% SVL); (16) midbody diameter 18.0-27.3 mm (Figs 1 - 3 ).

Comparisons.

Among all 150 congeners known to date ( Uetz et al. 2023) Atractus paulus shares with only eight species a SVL larger than 600 mm: A. atlas Passos, Scanferla, Melo-Sampaio, Brito & Almendariz, 2019, A. gigas Myers & Schargel, 2006, A. obesus Marx, 1960, A. pachacamac Melo-Sampaio, Passos, Prudente, Venegas & Torres-Carvajal, 2021, A. serranus Amaral, 1930, A. torquatus Duméril, Bibron & Duméril, 1854, A. touzeti Schargel, Lamar, Passos, Valencia, Cisneros-Heredia & Campbell, 2013, and A. trihedrurus Amaral, 1926. Except for Atractus serranus , all other species have dorsal bands, differing from the uniform dorsum of A. paulus (Figs 2 , 4 ). In addition, other diagnostic features between A. paulus and species with specimens recorded above 600 mm SVL were provided in table 1 of Passos et al. (2010). However, inasmuch as size has evolved independently in various clades ( Arteaga et al. 2017; Melo-Sampaio et al. 2019 a, 2021a; Arteaga et al. 2022). None of those giant species shares the presence of two apical pits on dorsal scales, so we restrict the comparisons to two species possessing two apical pits on dorsal scales and occurring at high elevations in montane forest of the eastern Andes: Atractus duboisi (Boulenger, 1880) and Atractus orcesi Savage, 1955 (Figs 5 , 6 ).

We did not directly examine the holotype of Atractus ecuadorensis Savage, 1955 and Atractus resplendens Werner, 1901, so it is not known whether they have apical pits, likewise, it does not allow us to conclude that these species constitute a natural group with the previous ones (see Fig. 7 ). Although Arteaga et al. (2022) noticed that a black stripe on a yellow belly is a characteristic shared by A. duboisi , A. discovery , and A. orcesi , they mistakenly assumed that it is absent in A. resplendens . This is clearly stated to be present in the description given by Werner (1901).

Atractus paulus differs from A. duboisi by having 17 dorsal scale rows, dorsum uniformly reddish in adult specimens, eight supralabials with fourth and fifth entering orbit (vs. 15 dorsal scale rows, seven supralabials with third and fourth entering orbit, adults dark brown or black with yellowish paired paravertebral dots in A. duboisi ); from A. orcesi by having 17 dorsal scale rows, dorsum uniformly reddish in adult specimens (vs. 15 dorsal scale rows, dorsal colour dark brown with a cream- brown occipital band, vertebral and dorsolateral stripes in Atractus orcesi ).

Description of the holotype.

An adult female, SVL 830 mm, tail length 83 mm (9.1% of total length); head distinct from body; head length 22.6 mm (2.7% SVL); head width 19.8 mm (87.6% head length); rostral-orbit distance 9.3 mm; nostril-orbit distance 6.8 mm; interorbital distance 10.9 mm; head rounded in lateral view; snout sub-acuminate in dorsal view, truncate in lateral view; canthus rostralis not conspicuous; rostral subtriangular in frontal view, 4.6 mm wide, 3.0 mm high, slightly visible in dorsal view; internasal 2.5 mm long, 2.30 mm wide; internasal suture sinistral with respect to prefrontal suture; prefrontal 6.1 mm long, 4.9 mm wide; supraocular subtrapezoidal, 4.5 mm long, 3.4 mm wide at broadest point; frontal pyramidal, 7.0 mm long, 5.9 mm wide; parietal 10.8 mm long, 7.1 mm wide; nasal entirely divided, nostril well-spaced into both pre- and postnasal; prenasal 2.4 mm high, 1.5 mm long; postnasal 2.6 mm high, 2.5 mm long; loreal 5.0 mm long, 1.9 mm high; second, third and fourth supralabials contacting loreal on left side; third to fifth supralabials contacting loreal on right side; eye diameter 2.9 mm; pupil rounded; two postoculars similar in height, being upper longer than lower; upper postocular 2.2 mm long, 2.7 mm high; lower postocular 1.4 mm long, 1.6 mm high; temporal formula 1+2; first temporal 5.3 mm long, 4.3 mm high; upper posterior temporal, 5.6 mm long, 4.3 mm wide; supralabials nine, fifth and sixth contacting eye on right side, supralabials eight, fourth and fifth contacting eye on left side; first supralabial narrower (1.4 mm wide) than second (1.7 mm wide) and similar in height; third supralabial trapezoidal, similar in height and wider (2.1 mm) than second; sixth (right) and seventh supralabial taller (left) and seventh (right) and eighth longer (left) than remaining supralabials; symphysial subtriangular, 3.1 mm wide, 1.3 mm long; first pair of infralabials preventing contact symphysial-chinshields; infralabials eight (right) and seven (left), first four contacting chinshields; chinshields 8.9 mm long; gular scale rows four; preventrals four; ventrals 167; subcaudals 26/26 respectively from left to right side; dorsal scale rows 17/17/17, with apical pits at level of cloaca; midbody diameter 27.3 mm (3.3% of SVL); caudal spine 3.2 mm long, shorter than last fused subcaudal scale (2.8 mm). Maxillary bone arched upward anteriorly in lateral view, ventral portion curved on anterior and nearly flattened on median to posterior portion; maxillary with eight teeth; teeth angular in cross section, robust at base, narrower at apices, curved posteriorly; lateral process of maxilla well developed (Figs 2 , 3 ). Paratype ZFMK 89147 agrees in most of characters of holotype, differing only in colouration and scale counts (166) in venter.

Colour in life and preservative.

Passos et al. (2010) described the colouration as follows: dorsum and background of head mostly dark brown. We observed that dorsum and head are Raw umber (colour 23) with gradation to cinnamon in contact internasals-prefrontals (colour 21) becoming cinnamon rufous (colour 31) on snout region; supralabials cinnamon with small invasion of cinnamon rufous; mental and gular regions mostly dark brown, with few cream (colour 12) dots; venter light to dark brown, with few cream to greyish brown dispersed dots (colour 284); underside of tail dark brown. Ontogenetic variation is pronounceable (see fig. 2 of Passos et al. 2010), where juvenile has head and dorsal ground colour of body dark greyish brown to sepia (colour 286), with few dispersed buff (colour 5) stains almost forming a nuchal collar, cinnamon to chamois (colour 84) dots or barely distinct bands are present in dorsolateral region of body and tail. Posterior part of chishields and gular region is pale cinnamon (colour 55). Venter is sepia with dispersed pale cinnamon blotches; cloacal region is pale cinnamon; subcaudals sepia with stained pale cinnamon midventrally close to cloaca.

Distribution and natural history.

The new species is known from two close localities Alto Ihuamaca and El Chaupe, at elevations of 1641-2161 m in the northern portion of the Cordillera Occidental of the Andes, San Ignacio province, Cajamarca department, Peru (Fig. 8 ). Both localities are in agricultural areas with coffee plantations and pastures for cattle ranching with scattered small patches of montane forest and secondary vegetation. According to Passos et al. (2010), the adult female holotype was collected by day crossing a trail at the forest edge in an open area and the juvenile paratype inactive under a log near a coffee plantation. The holotype contained 12 eggs in the oviduct, measuring 30.4-36.3 mm (X = 33.7 mm) length and 14.516.3 mm (X = 15.5 mm) width ( Passos et al. 2010).

Etymology.

The species epithet “paulus” is a Latin word being patronym for our friend Paulo Gustavo Homem Passos. Dr. Paulo Passos has described more than 34 Atractus species, approximately one-fifth of the astonishing diversity of this complex genus. The Latin word “Paulus” also means “small” and thus, we also refer to the type series composed only by the holotype and paratype.

Remarks.

The montane forest below 2000 m in the San Ignacio province has almost disappeared owing to agricultural activities. Only scattered patches of montane forest and secondary vegetation can be observed in the landscape. The National Sanctuary Tabaconas Namballe is between approximately 5 and 9 km in a straight line from the localities of Atractus paulus preserve forests from 2000 m. Even other protected private areas in San Ignacio possess most of their natural surfaces above 2000 m.

However, due to scarcity of knowledge about the distribution of this new species, especially its altitudinal range, we could not objectively propose a conservation category based on the IUCN criteria, but due to the levels of habitat destruction in the area efforts should be allocated for the conservation status of this species to be rapidly reassessed.

Figures

Figure 1. Dorsal (A) and ventral (B) view of Atractus paulus holotype CORBIDI 877.

Figure 2. Dorsal pattern of juveniles for comparison: A A. gigas MEPN 8706 and B A. paulus.

Figure 3. Comparison of holotypes head in lateral, ventral and dorsal views. A-C Atractus gigas; D-F Atractus paulus. Note the contact of infralabials with chinshield (3 in A. gigas versus 4 in A. paulus).

Figure 4. Comparison of holotypes head in dorsal, ventral and lateral views. G-I Atractus atlas and J-L Atractus touzeti.

Figure 5. Apical pits in dorsal scales indicated by red arrows: A A. duboisi QCAZ 2759 and B A. orcesi QCAZ 2779.

Figure 6. Apical pits in dorsal scales indicated by red arrows in A A. duboisi QCAZ 3302 (QCAZ / bioweb) and B A. duboisi QCAZ 2801 (QCAZ / bioweb - CC BY-NC-ND 4.0); C A. zgap QCAZ 5183 (sensu Arteaga et al. 2022) and D A. orcesi QCAZ 2779. Apical pits indicated by yellow arrows in E, F Atractus paulus CORBIDI 877.

Figure 7. Holotypes: A Atractus resplendens ZMB 17414 and B Atractus ecuadorensis FMNH 23529 (Field Museum of Natural History - CC BY-NC 4.0).

Figure 8. Geographical distribution of giant groundsnakes. Triangles = Atractus atlas. Diamonds = Atractus gigas. Circles = Atractus paulus. Square = Atractus touzeti. Type localities are filled with a dot.