Atractus michaelsabini, Arteaga & Quezada & Vieira & Guayasamin, 2022

Arteaga, Alejandro, Quezada, Amanda, Vieira, Jose & Guayasamin, Juan M., 2022, Leaving no stone unturned: three additional new species of Atractus ground snakes (Serpentes, Colubridae) from Ecuador discovered using a biogeographical approach, ZooKeys 1121, pp. 175-210 : 175

Atractus michaelsabini sp. nov.

Figs 8 , 9 , 10f-h Proposed standard English name: Michael Sabin’s Ground Snake. Proposed standard Spanish name: Culebra tierrera de Michael Sabin.

Atractus roulei Savage, 1960: 68 (part).

Atractus lehmanni Arteaga et al., 2017: 97.

Holotype.

ZSFQ 4938 (Figs 8 , 9 , 10g ), adult male collected by Jorge Luis Romero at Corraleja, Azuay province, Ecuador (S3.3874, W79.22785; 2660 m).

Paratypes.

MZUTI 5289, adult female collected by Jorge Luis Romero at the type locality. AMARU 002 (Fig. 10f ), adult female collected by Jorge Luis Romero at the type locality. ZSFQ 4939 (Fig. 10h ), juvenile female collected by Jose Vieira and Amanda Quezada at El Panecillo, El Oro province, Ecuador (S3.46753, W79.48248; 2750 m). QCAZ 7887 and 7902, adult male and female collected by Silvia Aldás in December 2006 at Guanazán, El Oro province, Ecuador (S3.44667, W79.49051; 2663 m). QCAZ 9643 and 9652, adult females collected by Silvia Aldás in August 2009 at El Panecillo, El Oro province, Ecuador (S3.46753, W79.48248; 2775 m). DHMECN 7644-45, adult males collected by Mario Yánez-Muñoz, Luis Oyagata, Patricia Bejarano, and Marco Altamirano in March 2010 at Reserva Biológica Yunguilla, Azuay province, Ecuador (S3.22684, W79.27520; 1748 m). AMNH 18325, adult female collected in July 1920 at El Chiral, El Oro province, Ecuador (S3.63825, W79.59723; 1841 m). AMNH 22110-11, collected in August 1921 at La Chonta, El Oro province, Ecuador (S3.56585, W79.85144; 1025 m).

Diagnosis.

Atractus michaelsabini sp. nov. is placed in the genus Atractus , as diagnosed by Savage (1960), based on phylogenetic evidence (Fig. 1 ). The species is diagnosed based on the following combination of characters: (1) 15/15/15 smooth dorsals; (2) one postocular; (3) loreal 3 × longer than high; (4) temporals 1+2; (5) five or six supralabials, with (usually) third and fourth contacting orbit; (6) five or six infralabials, with (usually) first three contacting chinshields; (7) 9-13 maxillary teeth; (8) 1-3 rows of gular scales; (9) 1-3 preventrals; (10) 143-144 ventrals in males and 144-153 in females; (11) 24-31 subcaudals in males and 17-19 in females; (12) dorsal ground color golden yellow (Figs 8 , 10f-g ) to dark brown (Fig. 10h ) with each scale outlined in black, forming a reticulation; (13) venter yellowish with various degrees of brown stippling (Fig. 8b ); (14) 256-321 mm SVL in males and 201-392 mm SVL in females; (15) 35-42 mm TL in males and 21-37 mm TL in females.

Comparisons.

Atractus michaelsabini sp. nov. is compared to other members of the A. roulei species group: Atractus carrioni and A. roulei . From A. carrioni , the new species differs in having a loreal scale (Fig. 9c ) (absent in A. carrioni ). From A. roulei (Figs 10a-e ), the new species differs in having a dorsal pattern in which each scale is outlined in a thin black line, thus creating a reticulation, and by having the prefrontal scale in broad contact with the postnasal (Fig. 9c ) (not in contact or barely in contact in A. roulei ). Furthermore, the existence of the bright golden yellow morph in adult individuals has so far been recorded only in A. michaelsabini sp. nov.; not in A. roulei , where adults are dark brown dorsally (Fig. 10a-e ). In A. roulei , there is a black spot at the base of each dorsal scale, whereas in A. michaelsabini sp. nov. the spot is at the tip of each dorsal scale and is connected to the black reticulum. Genetic divergence in a 578 bp long fragment of the mitochondrial CYTB gene between A. michaelsabini sp. nov. and A. roulei is 6.5-7.2%, whereas intraspecific distances are 0-4.5% in A. michaelsabini sp. nov. and 0-4.8% in A. roulei .

Description of holotype.

Adult male, SVL 256 mm, tail length 39 mm (15.2% SVL); body diameter 7.4 mm; head length 10.7 mm (3.1% SVL); head width 6.4 mm (2.5% SVL); interocular distance 3.7 mm; head slightly distinct from body; snout-orbit distance 3.5 mm; rostral 1.9 mm wide, ca. as broad as high; internasals 1.0 mm wide; prefrontals 2.0 mm wide; frontal 3.0 mm wide, with a curvilinear triangular shape in dorsal view; parietals 2.9 mm wide (65% length); nasal divided; loreal 2.2 mm long, ~ 3 × longer than high; eye diameter 1.4 mm; pupil round; supraoculars 1.3 mm wide; one postocular; temporals 1+2; five supralabials, third contacting orbit; symphysial 1.7 mm wide, ~ 3 × as broad as long, separated from chinshields by first pair of infralabials; five infralabials, first three contacting chinshields; chinshields ~ 2 × as long as broad, posterior chinshields absent; dorsal scales arranged in 15/15/15 rows, smooth without apical pits; no preventrals; ventrals 143; anal plate single; 31 paired subcaudals.

Natural history.

Most individuals of Atractus michaelsabini sp. nov. have been found during the day hidden under rocks, mats of rotten vegetation, or buried in soft soil in pastures and maize plantations close to remnants of native forest. At night, they have been seen crossing forest trails. At the type locality, clutches of three or four eggs have been found under soil (Jorge Luis Romero, pers. comm.). Anecdotal information suggests that these snakes are more active during the rainy months (February-May at the type locality; Jorge Luis Romero, pers. comm.).

Distribution.

Atractus michaelsabini sp. nov. is endemic to an estimated 2,530 km2 area along the Pacific slopes of the Andes in southwestern Ecuador. The species occurs in the xeric inter-Andean valley of the Río Jubones as well as on the slopes of the Cordillera de Chilla. Atractus michaelsabini sp. nov. is known from provinces Azuay, El Oro, and Loja, and has been recorded at elevations between 927 and 2922 a.s.l. (Fig. 2 ).

Etymology.

The specific epithet Atractus michaelsabini is a patronym honoring a young nature lover, Michael Sabin, grandson of American philanthropist and conservationist Andrew “Andy” Sabin. The Sabin family is involved in conservation and field research of amphibians and reptiles and has protected over 264,365 acres of critical habitat throughout the world.

Conservation status.

We consider Atractus michaelsabini sp. nov. to be Endangered following the IUCN criteria B1a, b (i, iii) ( IUCN 2001), because the species’ extent of occurrence is estimated to be much less than 5,000 km2 (Fig. 2 ) and its habitat is severely fragmented and declining in extent and quality due to deforestation. Although A. michaelsabini sp. nov. is present in two protected areas (private reserves Buenaventura and Yunguilla of Fundación Jocotoco), nine of the 14 localities where the species has been recorded (Suppl. material 1: Table S1) are in heavily human-modified areas. Based on maps of Ecuador’s vegetation cover ( MAE 2012), we estimate that nearly 70% of the forest cover throughout the species’ potential distribution area has been destroyed, mostly due to the expansion of the agricultural frontier.

Figures

Figure 1. Phylogenetic relationships within Atractus inferred using a Bayesian inference and derived from analysis of 3,985 bp of DNA (gene fragments 16 S, CYTB, ND 4, C-MOS, NT 3, and RAG 1). Support values on intra-specific branches are not shown for clarity. Voucher numbers for sequences are indicated for each terminal. Black dots indicate clades with posterior probability values from 95 - 100 %. Grey dots indicate values from 70 - 94 %. White dots indicate values from 50 - 69 % (values <50 % not shown). Colored clades correspond to the species' distribution presented in the map of Fig. 2. New or resurrected species are indicated in bold type.

Figure 2. Distribution of Atractus arangoi, A. roulei, A. michaelsabini sp. nov., A. zgap sp. nov., and A. discovery sp. nov. in Ecuador and adjacent Colombia. White dots represent localities listed under Suppl. material 1. Each colored area is a geographic representation of the suitable environmental conditions for one of the clades recovered in the phylogeny of Fig. 1.

Figure 8. Adult male holotype of Atractus michaelsabini sp. nov. ZSFQ 4938 in a dorsal and b ventral view.

Figure 9. Head of the adult male holotype of Atractus michaelsabini sp. nov. ZSFQ 4938 in a dorsal b ventral c lateral right, and d lateral left view.

Figure 10. Photographs of living specimens of Atractus roulei and A. michaelsabini sp. nov. a A. roulei ZSFQ 4942 from Tixan, Chimborazo province, Ecuador b A. roulei ZSFQ 4944 from Tixan, Chimborazo province, Ecuador c A. roulei ZSFQ 4941 from Tixan, Chimborazo province, Ecuador d A. roulei ZSFQ 4945 from Tixan, Chimborazo province, Ecuador e A. roulei from Tixan, Chimborazo province, Ecuador f A. michaelsabini sp. nov. AMARU 002 from Corraleja, Azuay province, Ecuador g A. michaelsabini sp. nov. holotype ZSFQ 4938 from Corraleja, Azuay province, Ecuador and h A. michaelsabini sp. nov. ZSFQ 4939 from El Panecillo, El Oro province, Ecuador.