A new species of Oxyrhopus Wagler, 1830 (Serpentes: Dipsadidae) from the Bolivian Andes

: We describe a new dipsadine snake species, of the genus Oxyrhopus Wagler, 1830, from the highlands of Bolivia. Oxyrhopus emberti sp. n. is diagnosed from its congeners based on external and hemipenial morphology. The new species inhabits the humid forests of Yungas and Tucumano-Bolivian Forest highlands, between 1.200 – 1.800 meters above sea level, and is likely to be a Bolivian endemic. We also discuss the relationships of the new species with Andean congeners and provide a key to the identifi cation of the Oxyrhopus species from the Central Andes of Bolivia and Peru.


Comparisons
Characteristics from other species are presented in parentheses in this section.  . 1977, Cunha & Nascimento 1989, Silva Jr 1993, Freitas 2003.
Oxyrhopus emberti may be distinguished from O. rhombifer by preocular separated from frontal by supraocular and prefrontal contact (preocular in contact with frontal); white nuchal collar in juveniles (red in juveniles and adults); adults uniform black (black crossbands or triangles over incomplete red and white bands); hemipenis strongly bilobed with conspicuous pair of nude pockets in the lobular crotch (moderately bilobed, with moderately developed nude pockets) (Cei 1993, Zaher 1999, Freitas 2003. Oxyrhopus emberti may be distinguished from O. clathratus by presenting a nude area in lateral region of the tip of hemipenial lobes, five rows of enlarged spines, and organ Y-shaped (ornamented with papillate calyces, four rows of enlarged spines, either T or Y-shaped); adults uniform black (alternating red, white, and black crossbands, adults sometimes with black dorsum, with a white venter); (Zaher 1999, Bernardo et al. 2012 (Peters & Orejas-Miranda 1970).

Etymology
The specific epithet "emberti" is a noun in genetive case, and honours German herpetologist Dirk Embert, who has provided extensive contributions to the Bolivian Herpetology.

Hemipenial morphology
Strongly bilobed, bicalyculate, bicapitate, elongated, with lobes half as long as hemipenial body (Fig. 4). Lateral spines enlarged, in five rows, converging to distal ends of an enlarged crest, present on medial surface of both lobes. A pair of moderately developed naked pockets in the lobular crotch, under the enlarged crest. Sulcus spermaticus proximally bifurcated, dividing on proximal part of hemipenial body, becoming centrifugal, and conduced directly to upper portion of organ. Lobes are ornamented with papillate calyces, spinulate over border of capitulum. As in most of Oxyrhopus species, O. emberti sp. nov presents a nude area on lateral region of each lobe; in the new species, it is poorly developed.

Coloration
The 10 examined juvenile specimens (MNKR 2625, 3415, 3522, 3544, 3616, 4336, 4369, 4714, 4825, ZFMK 80615) of undetermined sex, and two juvenile females (MNKR 3506,3727), exhibited banded pattern, consisting of black body bands 17-29 and white body bands 16-21, black tail bands 6-11 and white tail bands 7-10); in one specimen, MNKR 3544, black color does not extend onto venter anteriorly; white bands 1-4 scales wide dorsally, wider on venter; separated by black bands of 4-17 scales; head black dorsally, with a broad and complete red or yellow nuchal collar in juveniles; one juvenile female (MNKR 3506, 537 mm total body length) is almost fully black, with a yellow gular region, and white body bands visible on the last body third and tail, dorsally and ventrally; the other juvenile female (MNKR 3727, 565 mm TTL) is completely black, with a yellow gular region.
Some small adult individuals (e.g. CBGR 0061, 1032 mm total body length) conserve red incomplete bands, although indistinct or vestigial, turning white on alcohol; an adult male (MNKR 1506, 450 mm) has a uniform black dorsum, and a dark yellow venter; all other adult individuals present uniform black dorsum and venter, with a pale yellow gular region; supralabials are black, and infralabials are pale yellow, as in the gular area; iris coloration red. In preservative, yellow turns white.

Geographic distribution and natural history
The new species is known only from humid rainforests, from 1.200-1.800 m above sea level. It is known from 11 localities, all in humid rainforests of Yungas and Tucumano-Bolivian ecorregions, and is currently endemic to Bolivia (Fig. 5).
Most specimens were collected during rainy season (June to February, 14 specimens), in March (2 specimens) and May (1 specimen). Three juvenile males were collected in May, November, and December. An adult female (MNKR 2058) collected in December contained nine eggs in its oviduct, while another (CBGR 0061) collected in November contained six eggs. A rodent (Muridae) was in the stomach content of a specimen (MNKR 2551, adult female). One juvenile specimen (MNKR 4336) has a second head, slightly malformed on the right side of the neck, slightly smaller than the normal head and seemingly non-functional.

DISCUSSION
The description of Oxyrhopus emberti sp. n. raises the number of valid Oxyrhopus species to 15. The genus Oxyrhopus presents an intricate taxonomic history and systematic relationships, being considered as polyphyletic (Zaher 1994, Sheehy et al. 2012, Figueroa et al. 2016. Although fitting the morphological diagnosis of Oxyrhopus (Peters & Orejas-Miranda 1970, Zaher 1999, an integrated taxonomic revision of Oxyrhopus is needed; noteworthy examples are O. marcapatae, that presents a strikingly different morphological characterization, differing from other Oxyrhopus species by presenting 15 dorsal rows, 7 supralabials, and 8 infralabials (vs. more than 15 dorsal rows with or without reduction, except for O. leucomelas, 8 or more supralabials except for O. leucomelas, 9 or more supralabials except for O. leucomelas), and O. leucomelas, which presents unique morphological characters (7 or 8 supralabials and infralabials, 17/17/15 dorsal rows) and shares hemipenial similarities and a similar coloration pattern with Siphlophis species (Zaher 1999, Lynch 2009, Sheehy et al. 2012.
The new species appears to be most morphologically similar to O. erdisii, which is currently known to its type locality, in the lowland Amazon Rainforests of the Macchu Picchu mountain range, Cusco department, southern Peru (Zaher & Caramaschi 2000). Both species share several similarities in hemipenial morphology (hemipenis elongated, strongly bilobed, bicalyculate, bicapitate, lobes ornamented with papillate calyces and spinules over the border of the capitulum, with poorly developed nude areas at the tip of lobes) and juvenile coloration pattern (both present monadal pattern and nuchal collars); we have also examined specimens of O. erdisii (Appendix 1) from the lowland Amazon Rainforests of Sandia, Puno department, southeastern Peru close to the Bolivia border, and unvouchered live specimen, tentatively assigned as Oxyrhopus cf. erdisii from the Yungas of Chulumani, La Paz department, in Bolivia, approximately 360 km S from the southernmost record (Fig. 7b clathratus occur in montane areas, the melanistic coloration may reflect an adaptation to increase thermoregulatory capacity, as there is a debate whether darker colors and its reflectance difference may influence a rate in which solar radiation is converted into body heat (see Forsman 1995, Bernardo et al. 2012.
The new species inhabits humid rainforests of Yungas and Tucumano-Bolivian ecorregions, and is currently endemic to Bolivia. Considering its restricted range, we suggest that O. emberti should be considered as a candidate for a threatened species status, and further assessments on its conservation and populational trends are warranted. In agreement with other authors (e.g. Zaher 1999, Zaher et al. 2009, we also highlight the need for a genus-wide systematic and taxonomic revision based on integrative data sets, to elucidate the phylogenetic relationships of this new species, and other exquisite congeners.