Vine snakes ( Oxybelis ) and Sharpnose snakes ( Xenoxybelis ) (Squamata, Serpentes) from lowlands of Bolivia, with first records of Oxybelis inkaterra for the country

We present information on the occurrence of colubrid vine snakes ( Oxybelis ) and dipsadid sharpnose snakes ( Xenoxybelis ) from the lowlands of Bolivia. These genera have been poorly reported from Bolivia and information presented herein includes nine new record provincials from the departments of Beni, Cochabamba, La Paz, Pando, and Santa Cruz, Bolivia. Moreover, we present the first records of Oxybelis inkaterra Jadin, Jowers, Orlofske, Duellman, Blair & Murphy, 2021 from Bolivia and we extend the known range of this species by approximately 207 km (Río Sipia, La Paz) and 628 km (Campamento Guacharos, Cochabamba) southeast of the type locality (Puerto Maldonado, Peru) in South America. In addition, we present morphometric information, meristic characters, coloration pattern, ecological aspects and natural history for the three species of vine snakes ( O. aeneus , O. fulgidus , O. inkaterra ) and two species of sharpnose snakes ( X. argenteus , X. boulengeri ) from the Bolivian lowlands.


Introduction
The genera Oxybelis Wagler, 1830 (Colubridae) and Xenoxybelis Machado, 1993 (Dipsadidae) comprise several widely distributed Neotropical colubrid species commonly known as vine snakes and sharpnose snakes, respectively (Arredondo et al. 2021;Uetz et al. 2023).Several species are sympatric in many regions of South America.However, Oxybelis has a much broader distribution that includes a northernmost distribution into the southern United States, whereas the northernmost distribution of Xenoxybelis occurs in southern Venezuela (Wallach et al. 2014;Nogueira et al. 2019;Uetz et al. 2023).
The nomenclatural history of the genus Oxybelis is long and convoluted (see Jadin et al. 2021).In addition, taxonomy within the genus has been unclear and disputed (Keiser 1974;Machado 1993;Jadin et al. 2019Jadin et al. , 2020)).Keiser (1974) maintained retaining Oxybelis aeneus (the type species for the genus) as a single species throughout its extensive range.However, Jadin et al. (2019Jadin et al. ( , 2020) ) presented compelling data that supported multiple species and considerable diversity; moreover, they proposed an O. aeneus complex to include six species with the description of two new species for Central America and northern South America.Additionally, new species within the complex have also been described from Ecuador (Torres-Carvajal et al. 2021) and Peru (Jadin et al. 2021); among them Oxybelis inkaterra Jadin, Jowers, Orlofske, Duellman, Blair & Murphy, 2021.The taxonomy of the genus Xenoxybelis has also been unclear and debated (see Melo-Sampaio et al. 2020).The genus was initially described by Machado (1993) and currently includes two species: Xenoxybelis argenteus (Daudin, 1803) and X. boulengeri (Procter, 1923) (Prudente et al. 2008;Melo-Sampaio et al. 2020; Uetz et al. 2023).Both species (X.argenteus and X. boulengeri) have been previously included in the genera Oxybelis (Peters and Orejas-Miranda 1970;Fugler et al. 1995) and Philodryas (Wallach et al. 2014;Nogueira et al. 2019).Oxybelis and Xenoxybelis, as reflected in their taxonomy, are not related but members of different colubrid families (Colubridae and Dipsadidae).However, they are a good example of convergence due to their arboreal lifestyle (e.g., morphology, coloration, diet, and habitat).
Herein we report information on the distribution and natural history for Bolivian vine snakes and sharpnose snakes, including the first confirmed records of Oxybelis inkaterra from Bolivia.
Scale counts, scutellation, and terminology follow Dowling (1951) and Peters (1964).Measurements were taken using a flexible ruler to the nearest millimeter (snout-vent length, SVL; tail length, TL; in the case of CIRAH after euthanasia).Dorsal scale row counts were taken at three standardized locations; head length behind occiput, midbody, and head length anterior to cloaca and separated by a script (-).Paired subcaudals were counted on one side only, average number of subcaudal and ventral scales in parentheses.In addition to the number of supralabials, the scales that make contact with the orbit are identified in parentheses (right/left).In addition to the number of infralabials, the scales that make contact with the first pair of chin shields are identified in parentheses (right/left).
For CIRAH specimens, we determined sex via cloacal probing and photographed each individual following the methodology outlined by Eversole et al. (2019).In addition, each specimen was weighed (g) with an electronic scale (Ohaus model HH 320).
We obtained geographic coordinates in decimal degrees using the Global Positioning System (Garmin eTrex, WGS84).We mapped the distribution of vine snakes and sharpnose snakes using Arc GIS software (ArcMap 10.2) including previous records cited in Tables 1, 3.

Results
We examined nine specimens of Oxybelis aeneus, six Oxybelis fulgidus, three Oxybelis inkaterra, one Xenoxybelis argenteus and seven Xenoxybelis boulengeri deposited in the Bolivian herpetological collections (Tables 1-4).The O. inkaterra record represents the first for Bolivia.We increased new locations of occurrence of these snakes for Bolivia and contributed information on some aspects of their natural history.
Coloration pattern.Upper region of head golden brown to tan; supralabials and ventral surface of head uniform cream color, the color transition is separated by a dark brown preocular line that extends from the nasal scale, under the eye, and toward the anterior region of the body.Black bars or spots present in the anterior region of the body; dorsal and ventral surface of the rest of the body relatively uniform light brown with scattered small black spots (Fig. 1A, B).
Coloration pattern.Upper region of the head green; supralabials and ventral surface of head yellowish green, the color transition is not separated by any line; it is evident from the rostral to the last supralabial.Dorsal surface of body uniform green; yellowish-green ventral surface with two yellow ventrolateral lines extending from the throat to the tail (Fig. 1C, D).
Ecological notes.The specimen CIRAH-929 was found capturing a bird in the crown of a pacay tree (Inga sp.) at an approximate height of 5.5 m from the ground.Found in a rural village, typical of Amazonian Bolivia, surrounded by secondary Amazonian forest where the harvesting of Brazilian nuts (Bertholletia excelsa) and the açaí palm (Euterpe oleracea) are common.Guacharos, El Palmar, Parque Nacional Carrasco (PNC).One adult male (CBF-4275) collected on 24 June 2015 from Río Sipia, PNyANMI Madidi.One adult (CBF-3780) date and location unknown (Table 1, Fig. 3).
Coloration pattern.Upper region of head is brown with dark brown to black mottling, black spots on posterior edge of nasal, and on preocular; black mottling on temporals forming an irregular postocular stripe that extends to second or third ventral; supralabials with mottling on borders, infralabials heavily mottled; mental, first pair of infralabials, and chin shields black with white spots (more intense in specimens CBF-3780 and MNKR-3740).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 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 eyespot markings; some of these markings also occur on the ventral and lateral portions of the tail (Fig. 2A-D).
Ecological notes.Specimen CBF-4275 was accidentally severed into two pieces by local guides while they were clearing work trails near the camp.The area has xeric and thorny vegetation, with representatives from the Bromeliaceae, Cactaceae, and Araceae families.This particular individual, feeling threatened, remained motionless, mimicking one of the branches of the shrub it was on.Unfortunately, this behavior caused it to go unnoticed by the guide, resulting in the unfortunate accident.4) and fourth and fifth contact the second pair of chin shields.
Coloration pattern.Upper center region of head brown; dorsolateral region of the head and supralabials light brown green, separated by broad grayish-green band, from nasal, crosses the eye, and extends to the body; ventral surface of the head yellowish green with scattered black points.Dorsal surface of the body light-greenish brown with two thin greenish-brown lateral bands; ventral surface bright yellowish green anteriorly and light green posteriorly with two lateral green bands (Fig. 4A, B).
Ecological notes.The specimen was found during the night resting on a branch of Piperaceae at a height 1.9 m off the ground in a secondary forest close to a stream.3, Fig. 5).
Coloration pattern.Upper center region of head brown; dorsolateral region of the head and supralabials yellowish green, separated by a dark brown band with black edges, from nasal, crosses the eye, and extends to the front of the body; ventral surface of the head yellowish green.Dorsal surface of the body with two thin dark greenish-brown lateral bands, the broad vertebral band light greenish-brown, the broad lateral bands light green (much brighter on the anterior part of the body); ventral surface uniform yellowish-green (Fig. 4C, D).
Ecological notes.The specimens were found resting (coiled) on tree branches between 0.5-2 m above the ground, during nocturnal searches between 1943-0036 h.The localities where they were found correspond to primary and secondary Amazonian forests of the Manuripi and Tahuamanu river sub-basin.

Discussion
Previous records of vine snakes (O.aeneus and O. fulgidus) collected in Bolivia include the departments of Beni, La Paz, Pando, and Santa Cruz (Fugler 1983;Fugler et al. 1995;Cadle and Reichle 2000;Quintana and Padial 2003;Nogueira et al. 2019;Eversole et al. 2021).This study increases the museum voucher material collected in lowlands of Bolivia by 13 additional records of O. aeneus (n = 7) and O. fulgidus (n = 6) for the departments of Beni, Cochabamba, La Paz, Pando, and Santa Cruz (Table 1, Fig. 3).It is likely that some records presented in this study correspond to the southern distribution limit of both species.
Furthermore, we report the first records of O. inkaterra for Bolivia, with specimens from the department of Cochabamba and La Paz (one specimen does not have a specific locality) and it constitutes the eighth and ninth locality of the species across its range (Table 1, Fig. 3).Oxybelis inkaterra was recently described by Jadin et al. ( 2021) within the O. aeneus complex, with specimens from Peru.Jadin et al. (2021) indicated that this species probably also occurs in Bolivia, Colombia and Brazil. Additionally, Torres-Carvajal et al. (2021) reported O. inkaterra from Ecuador.The specimens reported herein confirm the presence of O. inkaterra in Bolivia and extend the known distribution by approximately 207 km (Río Sipia) and 628 km (Campamento Guacharos, both localities located in protected areas) southeast of the type locality (Puerto Maldonado, Peru).
Previous records of sharpnose snakes (X.argenteus and X. boulengeri) collected in Bolivia include the departments of Beni, Cochabamba, and Pando (Procter 1923;Donoso-Barros 1967;Keiser 1989;Fugler et al. 1995;Cadle et al. 2003;Moravec and Aparicio 2005).Our report adds eight new records for X. argenteus (n = 1) and X. boulengeri (n = 7), all from the Amazonian forests of the department of Beni and Pando respectively (Table 3, Fig. 5), considering that the type locality of X. boulengeri is located to the south in the riparian forests of the Mamoré River, Trinidad, Beni (Procter 1923).Xenoxybelis boulengeri is considered rare and poorly represented in scientific collections (Prudente et al. 2008).
The meristic and morphological variation of O. aeneus has been well supported by Jadin et al. (2020) in its distribution range of the Amazon basin.The characters of the examined specimens of Bolivian O. aeneus (Table 2, Fig. 1A, B) are congruent with the description of the species by Jadin et al. (2020), and the color pattern (in life) matches the description of the species by Keiser (1989) and Jadin et al. (2020).
The meristic characters and color pattern (in life) of the examined specimens of O. fulgidus (Table 2, Fig. 1C, D) are congruent with the description of the species by Daudin (1803) and Boulenger (1896), and other related publications (Peters and Orejas-Miranda 1970;Nascimento et al. 1988;Cole et al. 2013;Fraga et al. 2013;Curlis et al. 2020).In addition, we contribute meristic data of the examined specimens, information scarcely available in the available literature.It is likely that the reduced number of subcaudals (128 scales) in the specimen CIRAH-929 is the result of the specimen having lost part of its tail at some point during its life.Specific meristic characters and coloration of O. inkaterra specimens reported in our study (Table 2, Fig. 2A-D) are congruent with the original description of the species by Jadin et al. (2021).However, specimen CBF-4275 has few eyespots in the posterior ventral and subcaudal region of the body; this is less evident in specimen MNKR-3740.Furthermore, this last specimen presents two supralabials that contact the orbit (fourth and fifth), unlike the other two specimens examined (fourth, fifth and sixth contact the orbit).
Our examined specimen of X. argenteus (Table 4, Fig. 4A, B) is consistent with the description and identification of the species by Daudin (1803) and Duellman (1978) respectively.In addition, we contribute with meristic data of the examined specimen.The absent loreal scale and undivided cloacal scale are specific characters of the species.
The mimicry of Oxybelis and Xenoxybelis with their environment is characteristic of this group of snakes, which is why it is very difficult to observe and capture them during the day.As a result, 91% of the specimens examined (CIRAH) were collected during the night, generally resting on branches or leaves of bushes at a height between 0-4 m from the ground.Only one specimen was found at ground level.
These new and first additional reports of Oxybelis and Xenoxybelis represent contributions that can be used to improve the understanding of their distribution (Figs 3,5) and aspects of their natural history in Bolivia and throughout their range in South America.In addition, they constitute valuable voucher specimens for Bolivian herpetological collections.

Table 1 .
Previous and additional records of vine snakes (O.aeneus, O. fulgidus) and first records of O. inkaterra for Bolivia.

Table 2 .
Meristic characters and scale counts of examined specimens of Oxybelis in the Bolivian herpetological collections.For abbreviations, see Materials and Methods.*=incomplete tail.

Table 4 .
Meristic characters and scale counts of examined specimens of Xenoxybelis in the Bolivian herpetological collections.For abbreviations, see Materials and Methods.*=incomplete tail.