Research Article |
Corresponding author: Paulo R. Melo-Sampaio ( prmelosampaio@gmail.com ) Academic editor: Oliver Hawlitschek
© 2023 Paulo R. Melo-Sampaio, Pablo J. Venegas.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Melo-Sampaio PR, Venegas PJ (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): 257-266. https://doi.org/10.3897/evolsyst.7.102578
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Based on an exhaustive revision of external morphological characters we describe a new species of Atractus from the humid montane forest of the Andes of northern Peru, Cajamarca department, occurring at elevations of 1641 to 2161 m. This new species was misidentified as A. gigas in the literature and for more than a decade represented the southernmost record of the that species. In the absence of molecular data and limited by a small sample, we use some underreported characters in the genus Atractus such as the presence of apical pits. Thus, the combination of apical pits as well as other characters mentioned in the literature (i.e., head scutellation and number of subcaudals) distinguishes the Peruvian population from A. gigas, and strongly supports the morphological separation of this taxon from the rest of its congeners.
Apical pits, Andes, endemism, morphology, scales, tubercles
During last five years, the taxonomy of the genus Atractus has improved notably with molecular data leading to systematization of this fascinating group of cryptozoic snakes in the tree of life (
Despite having a usually secretive habit that makes sighting by humans difficult, many species of Atractus are relatively large, reaching more than 600 millimeters (
Descriptions of “giant” Atractus in the Andes region are uncommon and primarily based on small samples (
Terminology for cephalic shields follows
We follow
Atractus gigas
non Myers & Schargel, 2006;
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.
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
Among all 150 congeners known to date (
Comparison of holotypes head in dorsal, ventral and lateral views. G–I Atractus atlas and J–L Atractus touzeti.
Apical pits in dorsal scales indicated by red arrows: A A. duboisi
Apical pits in dorsal scales indicated by red arrows in A A. duboisi
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.
Holotypes: A Atractus resplendens
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).
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
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.
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.
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.
The description of Atractus paulus raises questions and concerns about the lack of attention to detail in the use of some traditional morphological characteristics in snake taxonomy, such as the presence of apical pits, within the genus Atractus. The interest in making taxonomy increasingly integrative with the inclusion of molecular data combined with the need to publish data faster has minimized the use of informative and well-known character systems such as hemipenial morphology (
Based on previous phylogenetic results and the presence of apical pits, herein we name the Atractus duboisi group, including the following species: A. discovery, A. duboisi, A. orcesi, and A. paulus. Atractus discovery is tentatively assigned to this group based on molecular positioning retrieved in
Recent taxonomic revisions have improved knowledge about Atractus species described based on holotypes or small type series (
We thank Omar Torres-Carvajal and Fernando Ayala-Varela (
Atractus atlas (n = 4). ECUADOR: Zamora-Chinchipe: Paquisha: (MEPN 14203, holotype), Parroquía Guayzimi: (
Atractus duboisi (n = 63): ECUADOR: Napo: Baeza:
Atractus gaigeae (n = 1): ECUADOR: Orellana: Dayuma:
Atractus gigas (n = 5): ECUADOR: Cotopaxi: (FHGO 194, holotype), Las Pampas:
Atractus nigricaudus (n = 4): PERU: Pasco: Oxapampa: MUSM 17761, Parque Nacional Yanachaga-Chemillén: MUSM 31139. No data: MUSM 23467, MUSM 23500.
Atractus orcesi (n = 5): ECUADOR: Morona-Santiago: Río Hollin:
Atractus pachacamac (n = 28): ECUADOR: Napo: Sumaco Wildlife Sanctuary:
Atractus resplendens (n = 3): ECUADOR: no specific locality, probably Llanganate:
Atractus torquatus (n = 7): BRAZIL: Amazonas: Rio Marari:
Atractus typhon (n = 4): ECUADOR: Esmeraldas: Reserva Tesoro Escondido: QCAZR 14982–14984, QCAZR 14989.
Atractus ukupacha (n = 22): ECUADOR: Napo: El Chaco:
Atractus zgap (n = 2): ECUADOR: Napo: El Chaco: