Bev Ridgely’s Snail-Eater

Caracolera de Bev Ridgely

MZUTI 5416 (Figs 6, 7), adult male collected by Matthijs Hollanders on August 01, 2017 at Reserva Buenaventura, province of El Oro, Ecuador (S3.65467, W79.76794; 524 m).

AMNH 22092, adult male collected by George H. Tate on December 01, 1921 at Bucay, province of Guayas, Ecuador (S2.19788, W79.12909; 433 m). CORBIDI 3791, adult male collected by Pablo Venegas and Caroll Landauro on May 07, 2009 at El Caucho, department of Tumbes, Peru (S3.81438, W80.27101; 379 m). CORBIDI3792, adult female collected by Pablo Venegas and Caroll Landauro on May 07, 2009 at El Caucho, department of Tumbes, Peru (S3.81438, W80.27101, 379 m). CORBIDI 7894, adult female collected by Vilma Durán and Germán Chávez on October 21, 2010 at El Caucho, department of Tumbes, Peru (S3.81844, W80.26856; 478 m). CORBIDI7994, adult female collected by Pablo Venegas on September 24, 2010 at El Caucho, department of Tumbes, Peru (S3.81244, W80.26716; 481 m). DHMECN 8976, juvenile collected by Michael Harvey and Luis A. Oyagata at Cerro San Sebastián, Parque Nacional Machalilla, province of Manabí, Ecuador (S1.60002, W80.69974, 602 m). DHMECN 9483, adult male collected by Mario Yánez-Muñoz, María Pérez, Miguel Alcoser, Marco Reyes-Puig and Gabriela Bautista in 2012 at the type locality. DHMECN 10061, adult male collected by Manuel Morales, María Perez Lara and Karem López at Reserva Biológica Ayampe, province of Manabí, Ecuador (S1.65417, W80.81333; 43 m). DHMECN 11526, adult of undetermined sex collected by Juan Carlos Sánchez-Nivicela, Karem López, Verónica Urgilés, Bruno Timbe, Elvis Celi and Valentina Posse at Remolino, province of El Oro, Ecuador (S3.56551, W79.91948; 229 m). KU 152205, adult of undetermined sex collected at 30 km E Pasaje, province of Azuay, Ecuador (S3.31439, W79.57970; 561 m). MCZ R-17099, a juvenile of undetermined sex collected at Valle del Chanchán, province of Chimborazo, Ecuador (S2.27383, W79.08735; 697 m). MCZ R-3564, a juvenile of undetermined sex collected by Samuel Walton Garman on January 1, 1875 at Daule River, province of Guayas, Ecuador (S1.87009, W80.00530; 5 m). MZUA.RE.0142, adult female collected by Jose Manuel Falcón at Sarayunga, province of Azuay, Ecuador (S3.31431, W79.58069; 552 m). MZUA.RE.0328, adult male collected by Keyko Cruz on April 04, 2016 at Jauneche, province of Los Ríos, Ecuador (S1.33333, W79.58333; 41 m). MZUA.RE.0424, adult male collected by Fausto Siavichay, Valentina Posse and Xavier Clavijo on June 29, 2017 at 2 km N Palmales Nuevo, province of El Oro, Ecuador (S3.65158, W80.09625; 129 m). MZUTI 3269, adult male collected by Lucas Bustamante on November 07, 2013 at the type locality. QCAZ 14444, adult male collected by Fernando Ayala, Steven Poe and Chris Anderson on January 10, 2016 at Proyecto Minas San Francisco, province of Azuay, Ecuador (S3.30829, W79.47079; 862 m). QCAZ 14446, adult male collected by Fernando Ayala, Steven Poe and Chris Anderson on January 10, 2016 at Ponce Enríquez–El Coca, province of Azuay, Ecuador (S3.03197, W79.64615; 1206 m). ZSFQ D503, adult male collected by Diego Cisneros-Heredia on June 07, 2000 at Cerro La Mocora, Parque Nacional Machalilla, province of Manabí, Ecuador (S1.60379, W80.70191; 818 m).

Sibon bevridgelyi is placed in the genus Sibon based on phylogenetic evidence (Fig. 3) and on having the labial beneath primary temporal conspicuosly higher than other labials. The species differs from all described species of Sibon based on the following combination of characters: (1) 15/15/15 smooth dorsals with enlarged vertebral row (1.3–1.7 times as wide as adjacent rows); (2) seven supralabials with 4^th and 5^th contacting orbit or eight supralabials with 5^th and 6^th contacting orbit; (3) one pair of infralabials in contact behind symphysial; (4) postmental absent; (5) 175–193 ventrals in males, 193 in the single female; (6) 80–94 divided subcaudals in males, 98 in the single female; (7) dorsal and ventral ground color pale yellow with or without irregular black bands, and with a black stippled disruptive pattern of irregular rusty to reddish brown blotches that are separated from each other by light interspaces (Figs 6, 2b, c); bands incomplete and stippling not prominent or absent on ventral surfaces; head heavily speckled or blotched with black or rusty pigment; eyes light slate blue to pale goldenrod with black speckles and reticulations; (8) 349–732 mm SVL in males, 786 mm in the single female; (9) 124–268 mm TL in males, 204 mm in the single female.

Sibon bevridgelyi is most similar to S. nebulatus, from which it differs on the basis of its distinctive coloration (Figs 6, 2b, c). In S. nebulatus (Figs 2e, f), the dorsal and ventral color is a combination of mainly black to dark-brown blotches or bands on a gray to grayish brown background (interblotch) color; the dorso-lateral blotches can partly be bordered by white to rosy scales or edges. In some regions, the blackish pattern and gray ground color is often replaced by dark and light brown tones (e.g., in Venezuela, adjacent regions in Colombia, and Trinidad and Tobago); the spaces between the blotches are heavily invaded by blotch color and strongly stippled, spotted and mottled with white and black pigment. Although S. bevridgelyi also has a disruptive pattern, the diagnostic white and gray pigment of S. nebulatus from Central America and northern South America is lacking in S. bevridgelyi. Instead of white pigment, there is golden yellow; instead of gray, the dominant ground color is bright rusty brown to maroon. Additionally, the infralabials and the whitish throat in S. nebulatus from Central America and northern South America are heavily stippled or at least partly interrupted with black pigment, whereas in S. bevridgelyi the infralabials and the throat are immaculate or have few scattered blotches (Fig. 7b). Finally, the black blotches and stippling diagnostic of S. nebulatus are lacking in the majority of the specimens of S. bevridgelyi. Specimens of S. nebulatus with rosy gray or reddish brown ground color have white (instead of yellowish) blotches and stippling. Genetic divergence in a 521 bp long fragment of the mitochondrial Cytb gene between S. bevridgelyi and S. nebulatus leucomelas is 1.9–2.5%, whereas intraspecific distances are less than 0.4% in both species.

Adult male, SVL 602 mm, tail length 186 mm (31% SVL); head length 20.9 mm (3% SVL) from tip of snout to commissure of mouth; head width 12.4 mm (59% head length) taken at broadest point; snout-orbit distance 21 mm; head distinct from neck; snout short, blunt in dorsal and lateral outline; rostral 3.5 mm wide, broader than high; internasals 1.9 mm wide, broader than long; prefrontals 4.4 mm wide, longer than broad, entering orbit; supraocular 4.4 mm long, longer than broad; frontal 4.1 mm long, pentagonal and rounded, in contact with prefrontals, supraoculars, and parietals; parietals 7.7 mm long, longer than broad; nasal weakly divided, in contact with first three supralabials, loreal, prefrontal, internasal, and rostral; loreal 3.7 mm long, longer than high, entering the orbit; eye diameter 3.9 mm; pupil semi-elliptical; no preocular; two postoculars; temporals 1+3 on the right side, 2+3 on the left side; eight supralabials with 5^th and 6^th contacting orbit on the right side, seven supralabials with 4^th and 5^th contacting orbit on the left side; symphysial separated from chinshields by the first pair of infralabials; nine infralabials, 1–7 contacting chinshields; anterior pair of chinshields broader than long, posterior pair longer than broad; dorsal scales in 15/15/15 rows, smooth, without apical pits; 184 ventrals; 80 divided subcaudals; cloacal plate single.

Specimens of Sibon bevridgelyi have been found active at night (20h56–03h56) on arboreal vegetation 30–500 cm above the ground in secondary and primary semideciduous foothill forest, pastures, and cacao plantations, usually close to streams. QCAZ 14444 was found feeding on a snail. In captivity, MZUA.RE.0142 fed on slugs and snails. By daytime, one individual (not collected) was found hidden under tree bark, and another (ZSFQ D503) was found coiled on the center of a palm tree about 2 m above the ground. DHMECN 9483 was collected in sympatry with Dipsas andiana and D. bobridgelyi at Reserva Biológica Buenaventura.

Northwestern Peru in the department of Piura, and southwestern Ecuador in the provinces of Azuay, Chimborazo, El Oro, Guayas, Los Ríos and Manabí at elevations between 5 and 1206 m (Fig. 8).

The specific epithet honors the late Prof. Beverly S. Ridgely, life-long birder and conservationist, and father of Robert S. Ridgely, well known in Ecuadorian ornithological circles and co-author of The Birds of Ecuador. Though he never got to visit Buenaventura, from afar Bev continued to delight in the conservation successes of Fundación Jocotoco, which now owns and manages one of the few protected areas where the Vulnerable Sibon bevridgelyi is known to occur.

We consider Sibon bevridgelyi to be Vulnerable following B2a,b(i,iii) IUCN criteria (IUCN 2001) because its area of occupancy is estimated to be less than 2,000 km², it is known only from 15 patches of forest lacking connectivity between them, and its habitat is severely fragmented and declining in extent and quality due to deforestation. Furthermore, only three of the localities (Parque Nacional Machalilla, Reserva Buenaventura, and Reserva Ayampe) where S. bevridgelyi occurs are currently protected.

Bob Ridgely’s Snail-Eater

Caracolera de Bob Ridgely

MZUTI 5417 (Figs 9, 10), adult male collected by Matthijs Hollanders on August 01, 2017 at Reserva Buenaventura, province of El Oro, Ecuador (S3.65467, W77.76794; 524 m).

DHMECN 11527, adult female collected by Juan Carlos Sánchez-Nivicela, Karem López, Verónica Urgilés, Bruno Timbe, Elvis Celi and Valentina Posse at Remolino, province of El Oro, Ecuador (S3.56551, W79.91948; 229 m). MZUTI 3266, adult female collected by Lucas Bustamante on October 06, 2013. MZUTI 5414, adult male collected by Matthijs Hollanders and Paulina Romero on June 08, 2017. QCAZ 1706, adult male collected by Fernando Ayala, Steven Poe, and Chris Anderson on March 03, 1994 at Ponce Enríquez, province of Azuay, Ecuador (S3.06547, W79.74358; 39 m).

Dipsas bobridgelyi is placed in the genus Dipsas based on phylogenetic evidence (Fig. 3), and the absence of a labial that is noticeably higher than other labials and in contact with the postocular, primary, and secondary temporals. The species differs from all described species of Dipsas based on the following combination of characters: (1) 15/15/15 smooth dorsals with enlarged vertebral row (2.1–2.2 times as wide as adjacent rows); (2) loreal and prefrontal in contact with orbit; (3) 9 supralabials with 4^th and 5^th contacting orbit; (4) one pair of infralabials in contact behind symphysial; (5) 180–201 ventrals in males, 178–184 in females; (6) 95–117 divided subcaudals in males, 96–98 in females; (7) dorsal and ventral color made up of 30–35 bold black body rings (up to 7–12 vertebral scales long) separated from each other by narrow (up to 3–4 vertebral scales long) dingy white interspaces; dorsal aspect of interspaces heavily speckled with rusty and black pigment; ventral surfaces lacking speckling; ground color of head dingy white with various degrees of scattered black pigment that coalesce on the top of the head, and various degrees of rusty speckling concentrated on the snout, nape and sides of the head; iris rich dark brown; (8) 372–478 mm SVL in males, 286–404 mm in females; (9) 158–212 mm TL in males, 117–158 mm in females.

Dipsas bobridgelyi is most similar to D. gracilis, from which it differs in coloration. In D. gracilis (Figs 1h, i), the black rings are up to 10–16 vertebral scales long and the interspaces are up to 5–7 scales long, whereas in D. bobridgelyi the black rings and interspaces are shorter, up to 8–9 and 3–4 vertebral scales long, respectively. In D. gracilis, the head plates are either completely black or black scattered with reddish brown, whereas in D. bobridgelyi the head plates are heavily stippled with white and tan pigment, especially on the prefrontals and internasals. In all known specimens of D. bobridgelyi, the ground color of the interspaces is white with contrasting reddish-tan pigment in the center, whereas in D. gracilis the ground color of the light interspaces on body and tail is either completely light brown or light reddish white, gradually becoming reddish brown towards the center. Finally, the nape and temporal region of the head in D. gracilis are either immaculate light reddish brown or marked with bold black speckles, whereas in D. bobridgelyi they are an irregular mix of fine speckling of white, rusty, and black pigments. Genetic divergence in a 689 bp long fragment of the mitochondrial Cytb gene between D. bobridgelyi and D. gracilis is 8.7–9.0%, whereas intraspecific distances are less than 0.3% in both species.

Adult male, SVL 372 mm, tail length 158 mm (43% SVL); head length 15.1 mm (4% SVL) from tip of snout to commissure of mouth; head width 8.1 mm (54% head length) taken at broadest point; snout-orbit distance 4.3 mm; head distinct from neck; snout short, blunt in dorsal and lateral outline; rostral 2.4 mm wide, broader than high; internasals 2.3 mm wide, broader than long; prefrontals 2.5 mm wide, longer than broad and contacting orbit; supraocular 3.2 mm long, longer than broad; frontal 3.9 mm long, hexagonal, in contact with prefrontals, supraoculars, and parietals; parietals 4.7 mm long, longer than broad; nasal divided, in contact with first three supralabials, loreal, prefrontal, internasal, and rostral; loreal 1.8 mm long, slightly higher than long, entering the orbit; eye diameter 2.7 mm; pupil semi-elliptical; no preocular; two postoculars; temporals 2+3; nine supralabials, 4^th and 5^th contacting orbit; symphysial separated from chinshields by the first pair of infralabials; 13 infralabials, 1–7 contacting chinshields; anterior pair of chinshields longer than broad, posterior pair broader than long; dorsal scales in 15/15/15 rows, smooth, without apical pits; 182 ventrals; 101 divided subcaudals; cloacal plate single.

Individuals of Dipsas bobridgelyi have been found active at night (19h00–23h26) on arboreal vegetation 100–250 cm above the ground in secondary semi-deciduous foothill forest. MZUTI 5414 was found feeding on a snail.

Foothills of the southwestern Ecuadorian Andes in the provinces of Azuay and El Oro, and northwestern Peruvian Andes in the department of Tumbes, at elevations between 39 and 572 m (Fig. 4).

This species is named in honor of Dr. Robert “Bob” S. Ridgely, a leading ornithologist and distinguished conservationist who has dedicated almost 50 years of his life to the study and conservation of birds and biodiversity across Latin America. Bob is the President of Rainforest Trust and for the past twenty years has been a major driver of conservation in Ecuador through Fundación Jocotoco, which he helped establish twenty years ago. In 1980, Bob visited the type locality of Dipsas bobridgelyi (Buenaventura, meaning "good fortune"), now known to be a key area for the conservation of biodiversity. Bob embarked on conservation and worked diligently to raise funds through Rainforest Trust for the past 18 years to purchase private properties and establish what is now the Reserva Buenaventura of Fundación Jocotoco.

We consider Dipsas bobridgelyi to be Endangered following the IUCN criteria B1a,b(i,iii) (IUCN 2001) because its extent of occurrence is estimated to be less than 5,000 km², it is known only from 4 patches of forest lacking connectivity between them, and its habitat is severely fragmented and declining in extent and quality due to deforestation. Furthermore, only two of the localities (Buenaventura reserve and Reserva Nacional de Tumbes) where D. bobridgelyi occurs are currently protected.

Cadle (2005) and Harvey (2008) examined MUSM 17589 from Tumbes department, Peru, and concluded that it was Dipsas gracilis. Although we did not examine this specimen, we believe that it corresponds to D. bobridgelyi based on Cadle’s (2005) color description (i.e., head white with many irregular black markings on the top and sides).

George Jett’s Snail-Eater

Caracolera de George Jett

MZUTI 5411 (Figs 11, 12), adult male collected by Melissa Costales on August 31, 2017 at Cabuyal, province of Manabí, Ecuador (S0.19698, W80.29059; 15 m).

DHMECN 11639, adult male collected by Jacinto Bravo in 2014 at Montecristi, province of Manabí, Ecuador (S1.04694, W80.65766; 136 m). DHMECN 11646, adult male collected by Félix Almeida in 2014 at Rocafuerte, province of Manabí, Ecuador (S0.92371, W80.45212; 19 m). MZUA.RE.0121 and MZUA.RE.0122, adult female and adult male, respectively, collected by Juan Carlos Sánchez-Nivicela at El Aromo, province of Manabí, Ecuador (S1.04665, W80.83227; 295 m). QCAZ 10589, adult male collected at El Aromo, province of Manabí, Ecuador (S1.04665, W80.83227; 295 m). QCAZ 9125, adult male collected at Cerro Blanco, province of Guayas, Ecuador (S2.17465, W80.02135; 147 m). USNM 142595, juvenile of undetermined sex collected on December 1959 at 10 mi N of Guayaquil, province of Guayas (S1.96418, W79.87988; 5 m). ZSFQ D606, juvenile male collected by Diego F. Cisneros-Heredia at the foothills of Cerro La Mocora, Parque Nacional Machalilla, province of Manabí, Ecuador (S1.59817, W80.75431; 308 m).

Dipsas georgejetti is placed in the genus Dipsas based on phylogenetic evidence (Fig. 3) and the absence of a labial that is noticeably higher than other labials and in contact with the postocular, primary and secondary temporals. The species differs from all described species of Dipsas based on the following combination of characters: (1) 15/15/15 smooth dorsals with a slightly enlarged vertebral row (1–1.4 times as wide as adjacent rows); (2) loreal and prefrontal in contact with orbit; (3) 7 supralabials with 4^th and 5^th (3^th–5^th in DHMECN 11646) contacting orbit; (4) no infralabials in contact behind symphysial; (5) 172–180 ventrals in males, 177 in one female; (6) 69–86 divided subcaudals in males, 58 in one female; (7) dorsal ground color light sandy brown with a pattern of 53–61 drab to brown black-edged middorsal blotches that are wider (6–7 vertebral scales long) and solid down to the edges of the ventrals on the first one third of the body, but becoming narrower (1–3 vertebral scales long) and broken up laterally towards the tail; interspaces finely speckled with brown pigment; ground color of the head light sandy brown with bold dark brown to black irregular blotches scattered on head plates and edging supralabials; ventral surfaces sandy brown with fine black speckling; iris sandy brown with dense dark brown speckling; (8) 270–711 mm SVL in males, 856 mm in one female; (9) 87–170 mm TL in males, 150 mm in one female.

Dipsas georgejetti is most similar to D. oswaldobaezi, D. williamsi, D. oligozonata, and D. vagrans, in that order, all of which were previously included in the genus Sibynomorphus. From D. oswaldobaezi (Figs 13, 14) and D. williamsi, it differs in having 7 supralabials with 4^th and 5^th bordering the eye (instead of 6 with 3^rd and 4^th bordering the eye). It further differs from D. williamsi in having the first supralabial not in contact with prefrontal (vs. in broad contact in D. williamsi). From D. oligozonata (Fig. 1o) and D. vagrans, it differs in having more than 160 ventrals. Dipsas georgejetti further differs from D. oligozonata in having distinct bold crossbands at least middorsally along the whole length of the body, instead of being present only on the anterior half of the body. Genetic divergence in a 529 bp long fragment of the mitochondrial Cytb gene between D. georgejetti and D. oswaldobaezi is 8.3%, whereas intraspecific distances are less than 0.4% in D. georgejetti. For the same fragment, the distance between D. georgejetti and D. williamsi is 7.8–7.9%.

Adult male, SVL 315 mm, TL 87 mm (28% SVL); head length 13.6 mm (4% SVL) from tip of snout to commissure of mouth; head width 8.4 mm (62% head length) taken at broadest point; snout-orbit distance 3.5 mm; head distinct from neck; snout short, blunt in dorsal and lateral outline; rostral 2.0 mm wide, broader than high; internasals 1.7 mm wide, broader than long; prefrontals 2.5 mm wide, longer than broad and contacting orbit; supraocular 3.4 mm long, longer than broad; frontal 3.3 mm long, pentagonal, in contact with prefrontals, supraoculars, and parietals; parietals 5.5 mm long, longer than broad; nasal divided, in contact with first two supralabials, loreal, prefrontal, internasal, and rostral; loreal 1.7 mm long, slightly higher than long, entering orbit; eye diameter 2.8 mm; pupil semi-elliptical; no preocular; two postoculars; temporals 2+2; seven supralabials, 4^th and 5^th contacting orbit; symphysial in contact with first pair of chinshields; nine infralabials, 1–6 contacting chinshields; anterior pair of chinshields longer than broad, posterior pair broader than long; dorsal scales in 15/15/15 rows, smooth, without apical pits; 178 ventrals; 69 divided subcaudals; cloacal plate single.

The holotype was active during a dry night after a sunny day. It was perched on tangled vegetation 130 cm above the ground in dry shrubland besides recently cleared pasture. MZUA.RE0121 and MZUA.RE0122 were found actively moving at night between the branches 80–200 cm above the ground. ZSFQ D606 was found active during daytime after bulldozers opened a track in old-growth forest.

Deciduous and semideciduous forests along the central Pacific coast in Ecuador in the provinces of Manabí and Guayas, at elevations between 5 and 317 m (Fig. 5).

The specific name georgejetti honors George Jett, who has been a long-time donor to Rainforest Trust and has supported the reserves of Fundación Jocotoco in Ecuador. He is an international traveler with a passion for reptiles, amphibians, and birds.

We consider Dipsas georgejetti to be Vulnerable following the IUCN criteria A1c,B1a,b(iii, iv) (IUCN 2001) because its extent of occurrence is estimated to be 10,193 km², it is known only from 9 localities effectively corresponding to 4 patches of forest lacking connectivity between them, and its habitat is severely fragmented and declining in extent and quality due to deforestation. At the type locality, D. georgejetti was found in a patch of deciduous forest of 13 km² that was being cleared to accommodate cattle pastures. One of the localities, 15 km N of Guayaquil, where D. georgejetti was collected in 1959, is now completely deforested, which suggests that this arboreal species is no longer present there.

Figure 5. 

Distribution of Dipsas georgejetti, D. oligozonata, D. oswaldobaezi, and D. williamsi in Ecuador and Peru. Figures represent known localities.

Figure 6. 

Adult male holotype of Sibon bevridgelyi. MZUTI 5416.

Oswaldo Báez’ Snail-Eater

Caracolera de Oswaldo Báez

QCAZ 10369 (Fig. 13), adult female collected by Silvia Aldás and Gabriel Zapata on March 03, 2010 at Quebrada El Faique, province of Loja, Ecuador (S4.17889, W80.04226; 1004 m).

BMNH1935.11.3.108, adult female collected by Clodoveo Carrión in the valley of Catamayo, province of Loja, Ecuador (S3.98064, W79.35928; 1289 m). MUSM 2192, adult male collected by Otavio Ruíz in Piura (department or city not specified), Peru. MZUA.RE.0286, adult of undetermined sex collected by Valentina Posse on December 2015 at Huaquillas, province of El Oro, Ecuador (S3.54115, W80.08646; 39 m). QCAZ 14051, adult of undetermined sex collected by Paul Székely and Diana Székely on March 18, 2015 at Reserva Ecológica Arenillas, province of El Oro, Ecuador (S3.62110, W80.17513; 41 m). QCAZ 14060, adult of undetermined sex collected by Paul Székely and Diana Székely on June 16, 2015 at Guabillo, province of El Oro, Ecuador (S3.60346, W80.18139; 44 m). QCAZ 15108, adult female collected by Diego Almeida, Darwin Núñez, Eloy Nusirquia, Santiago Guamán and Guadalupe Calle on November 12, 2016 at Reserva La Ceiba-Pilares, province of Loja, Ecuador (S4.27502, W80.32805; 534 m) (Fig. 14).

Dipsas oswaldobaezi is placed in the genus Dipsas based on phylogenetic evidence (Fig. 3) and the absence of a labial that is noticeably higher than other labials and in contact with the postocular, primary and secondary temporals. The species differs from all described species of Dipsas based on the following combination of characters: (1) 15/15/15 smooth dorsals with a slightly enlarged vertebral row (1–1.2 times as wide as adjacent rows); (2) loreal and prefrontal in contact with orbit; (3) six supralabials with 3^rd and 4^th contacting orbit; (4) no infralabials in contact behind symphysial; (5) 163–179 ventrals in males, 177–179 in females; (6) 68–70 divided subcaudals in males, 65–66 in females; (7) dorsal ground color light sandy brown with a pattern of 55–63 drab to brown black-edged middorsal blotches that are wider (7–9 vertebral scale rows) and solid down to the edges of the ventrals on the first one third of the body, but becoming narrower (1–3 vertebral scales long) and broken up laterally towards the tail; interspaces finely speckled with brown pigment; ground color of the head light sandy brown with a thin light cream nuchal collar and bold dark brown to black irregular blotches scattered on head plates and edging supralabials; ventral surfaces sandy brown with fine black speckling (Fig. 13b); iris sandy brown with dense dark brown speckling; (8) 277–348 mm SVL in males, 407–428 mm in females; (9) 85–114 mm TL in males, 110–122 mm in females.

Dipsas oswaldobaezi is most similar to D. williamsi, D. georgejetti, D. oligozonata, and D. vagrans, in that order, all of which were previously included in the genus Sibynomorphus. From D. williamsi, it differs in having 7–9 infralabials (vs. 10 in D. williamsi), first supralabial not in contact with prefrontal (vs. in broad contact in D. williamsi), and dorsal blotches that are lighter in the middle (vs. dark solid blotches). From D. georgejetti (Figs 11, 12), it differs in having 6 supralabials with 3^rd and 4^th bordering the eye (vs. 7 supralabials with 4^th and 5^th bordering the eye in D. georgejetti). From D. oligozonata (Fig. 1o) and D. vagrans, it differs in having more than 160 ventrals. Dipsas oswaldobaezi further differs from D. oligozonata in having distinct bold crossbands at least middorsally along the whole length of the body, instead of being present only on the anterior half of the body. Genetic divergence in a 529 bp long fragment of the mitochondrial Cytb gene between D. oswaldobaezi and D. williamsi is 4.0–4.2%, whereas intraspecific distances are less than 0.2% in D. williamsi. For the same fragment, the distance between D. oswaldobaezi and D. georgejetti is 8.3%.

Adult female, SVL 277 mm, tail length 85 mm (31% SVL); head length 9.5 mm (3.4% SVL) from tip of snout to commissure of mouth; head width 7.3 mm (76% head length) taken at broadest point; snout-orbit distance 3.3 mm; head distinct from neck; snout short, blunt in dorsal and lateral outline; rostral 2.1 mm wide, broader than high; internasals 1.2 mm wide, broader than long; prefrontals 2.2 mm wide, slightly broader than long and contacting orbit; supraocular 2.6 mm long, longer than broad; frontal 2.9 mm long, pentagonal, in contact with prefrontals, supraoculars, and parietals; parietals 4.2 mm long, longer than broad; nasal not divided, in contact with first supralabial, loreal, prefrontal, internasal, and rostral; loreal 1.3 mm long, longer than high, entering orbit; eye diameter 2.2 mm; pupil semi-elliptical; no preocular; two postoculars; temporals 2+2; 6 supralabials, 3^rd and 4^th contacting orbit; symphysial separated from chinshields by the first pair of infralabials; 9/8 (right/left) infralabials, 1–6/1–5 contacting chinshields; both pairs of chinshields longer than broad; dorsal scales in 15/15/15 rows, smooth, without apical pits; 179 ventrals; 70 divided subcaudals; cloacal plate single.

Individuals of Dipsas oswaldobaezi have been found active by night on vegetation or at ground level in forested environments, pastures, or rural gardens. One individual (QCAZ 15108) was found hidden under leaf litter during daytime. Two individuals (MZUA.RE.0286 and QCAZ 14060) were found dead on roads.

Deciduous and semideciduous lowland to lower montane forests and dry lowland shrublands in southwestern Ecuador (provinces of Loja and El Oro) and northwestern Peru (department of Tumbes), at elevation between 39 and 1289 m (Fig. 5).

The specific name oswaldobaezi honors Dr. Oswaldo Báez, a renowned Ecuadorian biologist and researcher who has dedicated his life to the teaching of science, scientific thinking, and the conservation of nature. Oswaldo Báez has played a major role in science education in Ecuador through many popular science articles and books.

We consider Dipsas oswaldobaezi to be Vulnerable following the IUCN criteria B1a,b(iii, iv) (IUCN 2001) because its extent of occurrence is estimated to be 8,605 km²; it is known only from eight localities effectively corresponding to four patches of forest lacking connectivity between them, and its habitat is severely fragmented and declining in extent and quality due to deforestation.

In his revision of Dipsas oligozonata, Cadle (2007) allocated three additional specimens (AMNH 110587, BMNH 1935.11.3.108 and MUSM 2192) to a species known only from the holotype (EPN 3612), collected at Zhila, province of Azuay (S3.50280, W79.18808; 2795 m) (Fig. 5). AMNH 110587 was collected ca. 34 km airline distance from the type locality at an elevation of 2204 m, and it resembles the holotype in both color and lepidosis. However, BMNH 1935.11.3.108 and MUSM 2192 have more than 160 ventral scales and have broad dark brown crossbars that are at least twice as long as those present in both the holotype, AMNH 110587 and in the other four specimens of D. oligozonata examined by us (Table 2; Fig. 1o), all of which have fewer than 160 ventral scales and come from elevations between 2102 and 2891 m in the watershed of the Río Jubones (Fig. 5). The coloration and ventral scale counts in BMNH 1935.11.3.108 and MUSM 2192 are more similar to D. oswaldobaezi, and we designated them as paratypes of this species.

Figure 7. 

Adult male holotype of Sibon bevridgelyiMZUTI 5416 in (a) dorsal and (b) ventral view. Scale bar: 1 cm.

Figure 8. 

Distribution of Sibon nebulatus and S. bevridgelyi in Ecuador. Figures represent known localities.