The Brown Vine Snake, Oxybelis aeneus, was until recently considered a single species, distributed from southern Arizona through the Neotropics into southeastern Brazil. However, newly conducted research restructured the species with a substantial taxonomic revision, recognizing five additional taxa (i.e. O. koehleri, O. microphthalmus, O. potosiensis, O. rutherfordi, O. vittatus) in this species complex. This revision focused on populations in North America, Central America, and northern South America while neglecting the southern portion of its distribution. Here, we examine the taxonomic history of the complex and use it along with specimen data to resurrect O. acuminatus from southeastern Brazil. Finally, we describe a new species from the Peruvian Amazon based on morphological characters. This work increases the species diversity of the O. aeneus complex to eight, and we expect further increases in biodiversity discoveries with continued exploration of the New World vine snakes.

Amazon, conservation, Inkaterra, morphology, new species, Serpentes, Squamata, South America, systematics, taxonomy

Widespread Neotropical snakes with distributions extending from North America to South America, occupy a variety of habitats and often contain unrecognized species diversity. Species such as the Boa constrictor (Reynolds and Henderson 2018), Chironius exoletus (Hamdan et al. 2017), and the Oxybelis aeneus complex (Jadin et al. 2019, 2020) occur in many important biogeographical areas such as the Chacoan, Paraná, Boreal Brazil, southern Brazil, southeastern Amazonia, Middle America, the Mexican Transition Zone, the Antilles, and the Pacific Coast. These distributions have populations on both sides of many extant biogeographic barriers that impede gene flow in the present day but may not have been isolating populations in the past (e.g. Daza et al. 2009, 2010; Jadin et al. 2012; Bagley and Johnson 2014). Additionally, some of these widespread taxa have complex nomenclatural histories, further challenging any attempts at revision.

The Brown Vine Snake, Dryinus aeneus Wagler, 1824, was described from a specimen collected at Ega, Brazil, (now Tefé, Brazil) on the south bank of the Amazon River at its junction with the Rio Tefé (Holotype ZSM 2645/0). Wagler was unaware that the generic name was preoccupied by Dryinus Latreille (1804), a Hymenopteran. Fitzinger (1826) used the combination Dryophis aeneus. Still, the generic name had been proposed previously by Dalman (1823) for the arboreal Asian snakes now in the genus Ahaetulla, but later rejected as invalid by ICZN Opinion 524. Subsequently, Wagler (1830) proposed the generic name Oxybelis but it did not gain common usage until the early 20^th century.

Bell’s (1825) description of Dryinus auratus (Fig. 1) on the basis of a specimen said to be from Mexico is likely in error. Günther (1858) reported 14 specimens of Dryiophis acuminata in the British Museum. Specimen b in Günther’s (1858:156) list is described as “Adult. Brazil? Presented by T. Bell Esq.” Keiser (1974) considered this specimen as the holotype of Bell’s D. auratus and comments that A.G.C. Grandison and L.C. Stuart concurred with him. However, Grandison reported the specimen was no longer in the BMNH collection (Keiser 1974), and the lost holotype is supported by Boulenger (1896) who listed all of the BMNH specimens with ventral and subcaudal counts. None of the counts come close to those in the specimen described by Bell. Keiser (1974) raised the issue of collectors not being active in Mexico until later in the 19^th century. Smith and Smith (1973) and Flores-Villela et al. (2004) discussed the history of herpetological collections in Mexico. The timing of Bell’s publication suggests that if the specimen was from Mexico it most likely would have been collected by the Sessé and Mociňo expedition (1788–1803). If the type specimen were indeed from “Mexico” it would share traits with populations described as being either from Western Mexico (O. microphthalmus) or Eastern Mexico (O. potosiensis). Bell’s original description suggests the snout was truncated, ventrals numbered 196, and subcaudals were 160. Jadin et al. (2020) found that populations from Eastern Mexico have a truncated snout but fewer than 190 ventrals and more than 160 subcaudals, though the tail tips of Bell’s specimen may have been broken as is often the case in vine snakes. The ventral and subcaudal counts fall within the range of those of O. microphthalmus, but those individuals do not have a truncated snout. Therefore, given the missing holotype, the lack of a detailed original description, and a questionable type locality, we are unable to allocate specimens to this name and consequently, we consider this name a nomen nudum.

Figure 1.

Illustration reproduced from Bell 1825 of Dryinus auratus from “Mexico”.

Wied (1824) described Coluber acuminatus (Holotype, AMNH 3886, Fig. 2) without reporting a type locality in the original description, though a second paper, Wied (1825:326), reported the specimen collected along the Río Espirito Santo in southeastern Brazil. He also remarks (rough translation) “Some differences notwithstanding it seems to me this snake is identical with Spix’s (1824) Dryinus aeneus…” Confusion over the publication date of Wied’s (1824) paper extended though most of the 19^th century (see Keiser, 1974 for a discussion). Schlegel (1837) recognized D. auratus and placed Wagler’s D. aeneus and Wied’s D. acuminatus as synonyms in error. Duméril et al. (1854) gave Wagler’s D. aeneus priority over D. acuminatus and D. auratus. That same year, Girard, 1854, described Dryophis vittatus based on USNM 7315 (Fig. 3) with a type locality of Taboga Island, Bay of Panama, Panama. By 1858 Günther had placed O. aeneus (Wagler, 1824), D. auratus Bell, 1825, and O. vittatus (Girard, 1854) in the synonymy of Dryiophis acuminata. And, Boulenger (1896), following Cope (1862) used the combination Oxybelis acuminatus because of continuing confusion over the publication date of Wied’s (1824) paper. Given that the type localities of O. acuminatus and O. aeneus are separated by 3200 km, it would seem likely that they are separate species.

Figure 2.

A, Illustration of Coluber acuminatus reproduced from Wied 1824. B, Holotype of O. acuminatus AMNH 3886.

Figure 3.

A, Illustration of Dryophis vittatus Girard 1854. B and C, in life photographs of O. vittatus from Panama (S. Lotzkat).

Barbour and Amaral (1926) described Oxybelis microphthalmus based on S. H. Beattie’s specimen (MCZ 22417) from Calabasas Canyon, in Santa Cruz County’s Pajaritos Mountains of Arizona; writing, “A large Oxybelis, similar in habit and coloration to O. acuminatus but differing from that species in having a much smaller eye and a much longer and differently shaped snout.” More recently, Oxybelis potosiensis was described by Taylor (1941), which has a type locality near Ciudad Maíz, San Luis Potosí, México (Holotype UIMNH 25069). Bogert and Oliver (1945) examined several characters found in the O. aeneus complex. They concluded recognizing two populations of O. aeneus: O. a. aeneus with a range extending from Guatemala to southeastern Brazil, and O. a. auratus with a range from southern Arizona, in the northwest of its distribution, and from San Luis Potosi at the northeast, southward to the Isthmus of Tehuantepec and the Yucatan Peninsula, thus synonymizing O. microphthalmus Barbour & Amaral, 1926 and O. potosiensis Taylor, 1941 into O. a. auratus.

Recently, Jadin et al. (2019) conducted the first significant phylogenetic study on Oxybelis and found strong support that O. aeneus sensu lato was a complex of species in drastic need of revision. Their work identified four novel taxa even as their dataset was restricted to populations in the northern part of the species’ distribution (i.e. Arizona, USA to Venezuela). However, they refrained from recognizing any additional species until morphological data could be included. Subsequently, Jadin et al. (2020) examinationed these populations to include morphology and more molecular data and removed O. microphthalmus, O. potosiensis, and O. vittatus from the synonymy of O. aeneus. Furthermore, Jadin et al. (2020) described O. koehleri from populations in Central America and O. rutherfordi from northern South America. They suggested that many more species would likely result from further investigation. Here, we inspect the clade further and resurrect O. acuminatus as a valid taxon from the Atlantic Coastal Forest of southeastern Brazil and describe a new species of Oxybelis from the Peruvian Amazon.

Our morphological analyses suggest distinctiveness among members of the Oxybelis aeneus complex, including O. acuminatus and specimens from Peru (Table 1). More specifically, our PCA produced five distinct groups: (1) O. rutherfordi, (2) O. vittatus and Peru, (3) O. aeneus, (4) O. potosiensis, and (5) O. acuminatus, O. koehleri, and O. microphthalmus (Fig. 4).

Figure 4.

Plot of PC-1 and PC-2 scores extracted from a Principle Components Analysis of twelve morphological characters, showing distinct clustering among geographically defined groups. Circular symbols represent Oxybelis acuminatus (red), O. aeneus (orange), O. koehleri (yellow), O. microphthalmus (light blue), O. potosiensis (green), O. rutherfordi (dark blue), O. vittatus (brown), and Peruvian specimens (gray).

Oxybelis inkaterra sp. nov.

http://zoobank.org/CC9C2A2E-8173-4F34-AC47-948543262969

Figs 5, 6, 7, 8, 9; Suggested English Name: Inkaterra Vine Snake; Suggested Spanish Name: Inkaterra Serpiente de vid

Oxybelis aeneus – Keiser, 1974:7;

Duellman 2005: 363, pl 205 has a photograph of a live specimen

Jadin et al. 2020: Fig. 1. has a photograph of a live specimen.

Holotype

KU 220196 (Figs 5, 6), from Peru, Madre de Dios: Cusco Amazónico (now Reserva Amazónica), Río Madre de Dios, c. 15 km E Puerto Maldonado, 200 m, 12°34'59"S, 69°4'59"W; collected by William E. Duellman (WED 59561), 21 December 1991.

Figure 5.

Holotype of Oxybelis inkaterra sp. nov., KU 220196 in life from Reserva Amazonica, formerly Cusco Amazonico, Peru (W.E. Duellman).

Figure 6.

Holotype of Oxybelis inkaterra sp. nov., KU 220196 preserved. A, Dorsal whole specimen; B, ventral whole specimen views; C, top of the head; D, profile. Scale bar: 1 cm.

Paratypes. KU 214887, Peru, Madre de Dios: Cusco Amazónico, Río Madre de Dios, c. 15 km E Puerto Maldonado, 200 m, 12°34'59.88"S, 69°4'59.879"W; collected by Erik R. Wild (Field number WED 59004), 23 December 1989; ZMH R01702, Peru, Huánuco: Pachitea, Panguana Biological Fieldstation, Rio Yuyapichis [= Rio Llullapichis], 260 m, approx. 9°41'S, 74°57'W, collected by János Regös July 1980.

Other material examined

FMNH 56141, from Peru, Loreto, Río Ucayali: Yarinacocha (c. 13°51'S, 71°1'W), collected by J.M. Schunke, 05 Sep 1946. FMNH 40085 (female), from the Madre de Dios area of Peru (no specific locality). ZMH R01611, Peru, Huánuco: Pachitea, Panguana Biological Fieldstation, Rio Yuyapichis [= Rio Llullapichis], 260 m, approx. 9°35'S, 74°56'W, collected by Carlos Vasquez Modena 1980.

Like other members of the Oxybelis aeneus complex O. inkaterra has an elongated head and body, 8–9 upper labials, four lower labials contacting the first pair of chin shields, 173–205 ventrals and 158–203 subcaudals; a divided anal plate, dorsal scales in 17–17–13 rows, and undivided hemipenes.

Diagnosis

A vine snake with (1) three upper labials (4–5–6) bordering the orbit; (2) numerous bold black bars and spots present on the body; (3) ventral surface mottled with dense black spots; (4) preocular shorter than eye diameter; (5) second pair of chin shields separated by smaller scales posteriorly; (6) nine upper labials, three located behind the orbit; (7) snout from above relatively broad, tapered, and flat rostrum; (8) supraocular and prefrontal are about the same length; (9) last upper labial about same length as primary temporal; (10) much of the lower surface of the head infused with black pigment; (11) second upper labial not in contact with preocular.

Comparison

Oxybelis inkaterra can be distinguished from the seven other members of the Oxybelis aeneus complex by the presence of, upper labials three and four are in contact the preocular; a head with an irregular, darkly pigmented ventral surface with pale spots; and eyespot markings on the posterior ventral surface of the body and tail; the snout of O. inkaterra is also relatively short and broad compared to other species in the Oxybelis aeneus complex (Fig. 7); the lack the brown-gray dorsal coloration seen in the other members of the complex. The dorsum is instead a dirty cream with black flecking (Figs 6, 8).

Figure 7.

A comparison between the snout shapes of Oxybelis aeneus (FMNH 64417) (top) and O. inkaterra (FMNH 56141) (bottom) (JCM).

Figure 8.

Referred specimen of Oxybelis inkaterra sp. nov., FMNH 56141 from Peru, Loreto, Rio Ucayali, Yarinacocha. A, profile; B, top of the head; C, bottom of the head.

Description of the holotype

A male with everted hemipenes (Fig. 6), SVL 732 mm, tail length 498 mm. Rostral broader than high, barely visible from above; upper labials 9/9; internasals paired, not extending past the posterior border of the first upper labial; prefrontals paired, in contact with upper labials 2 and 3; frontal, paired parietals, and supraoculars elongated and about 6 mm long, and in contact with supraoculars and upper postocular; postoculars 2/2; upper labials in contact with the preocular; 4–5–6 enter the orbit; 7–8–9 contact the primary temporal; 9 interrictals; one preocular less than the diameter of the eye; lower labials 10/10, first four in contact with the first pair of chin shields; second pair of chin shields longest; five paired gulars. Dorsal scales smooth in 17–17–13 rows. Ventrals 182; 165 divided subcaudals; anal plate divided.

In alcohol

Top of the head is brown with dark brown to black mottling (Figs 7, 8); black spot on posterior edge of nasal, and on preocular; black mottling on temporals forming an irregular postocular stripe that extends to second or third ventral; upper labials with mottling on borders, lower labials heavily mottled; mental, first pair of lower labials, and chin shields black with white spots; dorsal scales mottled with black and brown pigment in all rows; on anterior third of the body, some scales have heavy black pigment on their borders and form about 48 irregular transverse bands; anterior ventrals heavily mottled becoming fine stippling posteriorly; some ventrals mottled with scattered black spots anteriorly; posteriorly, these spots encircled with white pigment to form eye spot-like markings near the vent; some of these markings also occur on the ventral and lateral portions of the tail.

Coloration of the holotype in life

(Fig. 5). Field notes by W.E. Duellman on 21 December 1991: Dorsum and venter grayish tan with dark brown flecks and streaks. Top of head brown; lateral stripe on head dark brown, bordered below by white. Iris cream with horizontal dark brown stripe. Lining of mouth and throat black.

Variation

Whereas surrounding the black spots was not as pronounced in smaller individuals, KU 220196 has the first 33 ventral scales almost completely black (in preservative), but the stripes are still visible (Fig. 6). The black pigment extends onto the chin shields in varying amounts. The largest female was 1075 mm in total length; the largest male was 1278 mm. Two females had SVLs of 484 and 660 mm (x– = 572 mm SD = 88.0) with tails that were 0.62 and 0.63 of the SVL (x– =358.5, SD = 56.50). Two females (FMNH 40085, 56141) (had 184 and 191 ventrals (x– = 187.5, SD = 1.5). Eight upper labials, with 4–5–6 bordering the orbit. Usually 8–9 (nine on one side) lower labials, with four (usually) at first chin shield.

Distribution

This species occurs in the Amazonian rainforest of Peru in the departments of Huánuco, Loreto, and Madre de Dios. It is likely the species also occurs in Ucayali between these departments and possibly adjacent Bolivia, Brazil, and Colombia.

Ecology

At Reserva Amazónica, Oxybelis inkaterra is found in the dense vegetation on the bank of the Río Madre de Dios and in an adjacent clearing. The steep riverbank has vegetation unlike that of the adjacent rainforest. There are shrubby plants and no canopy; adjacent to the river are stands of the cane-like Gynerium saggitatum (Ponaceae). Oxybelis inkaterra is a diurnal arboreal snake, which, if like other members of the genus, has a fondness for small lizards. In the scrub forest adjacent to the river two species, Gonatodes humeralis (Sphaerodactylidae) and Anolis fuscoauratus (Dactyloidae), inhabit the scrub and probably are primary prey of the vine snake.

Field notes

KU 220196, weight 30.5 g, caught on the ground in camp during the day. Dorsum and venter grayish tan with dark brown flecks and streaks. Top of head brown; lateral stripe on head dark brown, bordered below by white. Iris cream with horizontal dark brown stripe. Lining of mouth and throat black. KU 214887, caught in bush 1.5 m above ground by day edge of river in camp. Mass 15 g, 895 mm TL.

Etymology

The specific epithet honors the ecotourism company Inkaterra (https://www.inkaterra.com/) and its non-profit NGO counterpart Inkaterra Asociación. These two institutions started in 1975 and 1978, respectively, were founded by José E. Koechlin von Stein to promote education and conservation of Peruvian culture and ecosystems. Inkaterra and Mr. Koechlin have been recognized numerous times with awards and accolades for providing sustainable ecotourism and research opportunities for scientists. The type locality, Cusco Amazónico (now Reserva Amazónica), is owned and operated by Inkaterra and is the site of one of the most thoroughly studied areas in the Neotropics, particularly for amphibian and reptile natural history (e.g. Duellman, 2005; Orlofske et al. 2012).

Notes on potential eyespots

Anti-predator adaptations in snakes are numerous and diurnal species can be expected to use visual coloration and behaviors to deter predators (Green, 1997). Eyespots are circular markings, often with concentric rings and conspicuous colors, that occur in many animals. They have been hypothesized to work as a way to startle or intimidate predators or they may work by being highly salient stimuli that promote sensory overload, biases, or neophobic reactions (Stevens and Ruxron 2014). Few snakes have been reported to have eyespots but Oxybelis inkaterra appears to be an exception and does exhibit ventral eyespots (Fig. 9). Although the markings are quite variable in size and definition, they are best developed in specimen FMNH 56141 from Yarinacocha, Peru. Given the absence of information in terms of how the snake uses these markings it is entirely possible that they simply make the snake more cryptic in its arboreal environment. However, the placement of the eyespots on the posterior ventral side of the body and on the tail suggests that they may be displayed in response to a predator.

Figure 9.

Referred specimen of Oxybelis inkaterra sp. nov., FMNH 56141 displaying eyespots on posterior ventral scales (left) and on subcaudal scales (right).

We thank T. Dowling and C. Johnson (ASU); A. Resetar (FMNH); L.J. Welton and R.M. Brown (KU); G.A. Rivas (MBLUZ); J. Rosado, T. Takahashi, and J. Hanken (MCZ); G. Bradley and P. Rienthal (UAZ); C.M. Sheehy III, D.C. Blackburn, M.A. Nickerson (UF); G. Schneider (UMMZ); C.J. Franklin, G. Pandelis, E.N. Smith, and J.A. Campbell (UTA); and M.G. Rutherford (UWIMZ) for allowing us to examine specimens under their care. We thank D.A. Kiziran and L. Vonnahme (AMNH) for photographs of the type specimen of Coluber acuminatus and S. Lotzkat for an in-life photograph of O. vittatus. We thank J. Hallermann (ZMH) for providing us data on specimens under his care. This manuscript was improved by reviews from J. Hallermann and E. Lehr. RCJ, SAO, and WED greatly appreciate the kind generosity of José E. Koechlin von Stein and the staff at Inkaterra for their friendship and support of our research over the years. MJJ was supported by the Portuguese Foundation for Science and Technology (FCT, SFRH/BPD/109148/2015).

Specimens examined

Museum acronyms follow Sabaj (2019).

Oxybelis aeneus – (n = 8) Brazil: FMNH 64417 Amazonas; FMNH 19203 Pará; KU R-124605, 124606, 140173, MCZ R-2582, 2778, and 53211 Pará.

O. brevirostris – (n = 2) Ecuador: UTA R-55952-53 Canton San Lorenzo: Parroquia Santa Rita, Esmeraldas.

O. inkaterra – (n = 6) Peru: FMNH 40085, Madre de Dios; FMNH 56141, Loreto, Rio Ucayali: Yarinacocha; KU R-214887 & R-220196 Madre de Dios, Cuzco Amazonico, 15 km E Puerto Maldanado; ZMH R01702 & R01611, Huánuco, Panguana Biological Station, Rio Yuyapichis [= Rio Llullapichis], Pachitea.

O. koehleri – (n = 34) Costa Rica: FMNH 179061 Cartago, Turrialba; El Salvador: FMNH 10997 Chalatenango; San Jose del Sacare, 3600′; FMNH 10998 Morazán, Divisadero; FMNH 64955, La Libertad, Volcan San Salvador, 1917 Lava, 500 m; FMNH 64956 La Paz, Los Blancos; KU 289907 Usulutan: Isla San Sebastian; Guatemala: FMNH 20088 Izabal: Bobos Plantation, near Playitas; FMNH 20171 and 20418 Sololá: Olas de Moca; UTA R-46795 Chiguimula; UTA R-45880 Huehuetenango; UTA R-22182–83, 33,040, 33,042, 37,256, 39,236, 42,433 Izabal; UTA R-37258 Peten; UTA R-46846 Zacapa, El Arenal; Honduras: FMNH 22231 Tela; FMNH 27050 San Pedro Sula; FMNH 34565, 34571, 34574, 34576, Bay Islands: Roatan, near Coxen Hole; UTA R-55231 Bay Islands: Roatan; FMNH 34770 Yoro, Portillo Grande; FMNH 40872 Gracias; UTA R-46865 Comayagua, Playitos: Aldea “Lo de Reina,” 785 m; UTA R-53176–78 Honduras: Gracias a Dios, Mocorón, 30–50 m. Nicaragua: UTA R-44838 Jinotega, El Paraíso Km 152.5, carretera Jinotega-Matagalpa, 1490 m.

O. microphthalmus – (n = 36) USA: Arizona: UAZ 47314 2.8 mi west of Sycamore Canyon; UAZ 519,225 miles east Sycamore Canyon, Ruby Rd.; UAZ 39544 Patagonia Mts.; Santa Cruz County: ASU 33314, ASU 33364, ASU 35069, ASU 35563, UAZ 16787, UAZ 39545; no specific locality: UMMZ 75779. Mexico: Colima: UTA R-57658; Guerrero UAZ 106056, 106058, 38448, 38451, 38455, 38461, 38467, 106051, 106057, 106059, 106054; Oaxaca: UAZ 106055, 117841–43, 178707, 178708; Sonora: UAZ 26972 0.5 miles West Alamos; UAZ 28279 8.8 miles east Alamos; Alamos UAZ 16797, UAZ 26973, ASU 06735, ASU 68990, ASU 88990; 35 miles east of Cannansa junction w/ Aqua Prieta Rd. UAZ 16796.

O. potosiensis – (n = 6) Mexico: UIMNH 25069 San Luis Potosí; UTA R-6107–10, 8752, and 12,368 S of Zapotitl, Puebla; UTA R-9014 6.0 mi E San Rafael, road to Rancho Nuevo, Tamaulipas.

O. rutherfordi – (n = 20) Tobago: FMNH 251213 Bloody Bay Rd., between Roxborough and Bloody Bay; Trinidad: FMNH 49973 no specific locality; FMNH 49974–75 Brickfield; FMNH 49976 Mount Harris, FMNH 49977–85 San Rafael; FMNH 215838 circa 3 miles S Simla-Quarry Rd., on Arima-Blanchisseuse Rd., egg farm; FMNH 215839 circa 2 miles S Simla-Quarry Rd., on Arima-Blanchisseuse Rd.; UTA R-64851 Arima Valley, William Beebe Tropical Research Centre, c. 6 km N Arima, 247 m; Venezuela: FMNH 17839–40 Puerto Viejo, Península de Paria, Sucre; MBLUZ 1268 between San Francisco de Macanao and Cerro Los Cedros, Isla de Margarita, Nueva Esparta.

O. vittatus – (n = 16) Panama: FMNH 152067 Almirante; FMNH 83552, 130674, 131314 Canal Zone: Summit; FMNH 161478 Canal Zone: Barro Colorado Island; FMNH 153665 Coiba Island; FMNH 170132 San Blas Territory: Soskantupu, 8°57'N, 77°44'W, 1 m; FMNH 154043 Bocas del Toro, 11 km NW Almirante 600 ft.; FMNH 154478, 154517 no locality data; MCZ R-22274, 22231, and 25118 Canal Zone; UF 65037, 65038, and 170469 Canal Zone.