Eutrachelophis bassleri, Myers & McDowell, 2014

Myers, Charles W. & McDowell, Samuel B., 2014, New Taxa And Cryptic Species Of Neotropical Snakes (Xenodontinae), With Commentary On Hemipenes As Generic And Specific Characters, Bulletin of the American Museum of Natural History 2014 (385), pp. 1-112 : 8-14

Eutrachelophis bassleri , new species Figures 1–3 , 10

Leimadophis sp. , Dixon and Soini, 1977: 54.

cf. Liophis sp. , Dixon and Soini, 1986: 114–115.

HOLOTYPE: AMNH R-52926, an adult male from Pisqui Hills , [upper] Río Pisqui , Province of Loreto, Peru, obtained by Harvey Bassler on January 15, 1927. The type locality is situated west of the Río Ucayali in the region of 8 ° 00– 8 ° 229 S, 75 ° 30–75 ° 509 W (see Remarks). This specimen (fig. 1A) is in good condition except that the maxillae and mandibles have been dissected out (possibly by Bassler), although still associated with the specimen. Total length 345 mm, tail length 101 mm; 2 preventrals (gulars wider than long), 133 ventrals + half ventral at anal plate, 67 pairs of subcaudals not counting terminal spine.

PARATYPES (11): ECUADOR: Pastaza Province: mouth Río Pucayacu , between Sarayacu and Montalvo, USNM 232826 (R. Olalla, Aug. 1948) ; Sarayacu, Río Bobonaza , USNM 232825 (R. Olalla, Nov. 1962) . PERU: Huánuco Province: [Río] Pachitea , AMNH R-52682 (H. Bassler, date?) ; Serranía de Sira, ridge above Río Llullapichis , 510 m (9 ° 299S, 74 ° 499W), NMW 31795 (M. Henzl and B. Wallnöver, May 20, 1988). Loreto Province: Mishana, TCWC 40555 , 41424 , 41425 (P. Soini; collected over an eight year period fide Dixon and Soini, 1986: 114) ; Pampa Hermosa, Río Cushabatay , AMNH R-55786 (H. Bassler, Sept. 1927) ; 2 Pebas, Río Ampiyacu , 250 ft., AMNH R-25193 (collector?) ; Río Tapiche , AMNH R-52441 (H. Bassler, Jan. 1928) ; upper Río Utuquinia , AMNH R-53473 (H. Bassler, Feb. 1928) .

ETYMOLOGY: The species is named in memory of Harvey Bassler (1883–1950), a former Research Associate in the American Museum’s Department of Herpetology. Bassler accumulated five of the 12 known specimens of this rare species during a decade devoted to petroleum exploration and zoo-

2 A catalog later compiled by Bassler at the American Museum bears an unexplained note indicating that this and three other snakes ‘‘may’’ have been obtained on the upper Río Marañón in September 1924. The Pampa Hermosa record is more in keeping with Bassler’s other Eutrachelophis records (all in Río Ucayali drainage) for this species, however, and it is the one plotted on the distribution map.

logical and ethnographic collecting in eastern Peru. 3

DIAGNOSIS: Eutrachelophis bassleri is a small snake (, 400 mm total length) that resembles the somewhat larger E. steinbachi (to 558 mm) in having 15 dorsal scale rows and conspicuous paired ocelli on the nape. It differs from steinbachi in having a postocular wedge of pale color extending dorsad from the lip, and in having a pale broken, posterior collar (the rounded upper ends of which often resemble a second pair of ocelli when viewed from above), and in lacking oblique pale dorsolateral markings touching the eye. E. bassleri further differs in having dorsolateral lines of vague dark spots (or fused crossbars) rather than dark anterior stripes; a lateral line of pale dashes or dots lies on scale row 4 in bassleri , on row 6 in steinbachi . Eutrachelophis bassleri differs radically from steinbachi in having an undivided hemipenis with a nude, dome-shaped apex.

DISTRIBUTION: Lowland rain forest in the western part of the Amazonian basin (map 1). Known localities for Eutrachelophis bassleri range from Pebas, Peru, on the upper Amazon River, northwestward to east-central Ecuador in the Río Bobonaza drainage, and southward in Peru through the Río Ucayali drainage to nearly 10 ° S. The species probably occurs also in extreme western Brazil and possibly in southern Colombia. There is an unnamed, clearly related species in central Amazonia, Brazil (see comments and illustration under Eutrachelophis species following Remarks).

DESCRIPTION OF TYPE SPECIMENS

Eutrachelophis bassleri is a small slender snake that probably is sexually mature by

3 Harvey Bassler was a petroleum geologist who spent a decade (1921–1931) exploring the upper tributaries of the Amazon, all the while making a magnificent herpetological collection, including 4200 snakes. His base of operations for upriver expeditions was Iquitos, where specimens were also obtained. He brought his collection to the American Museum in 1934, where he worked on his snakes up to World War II, when he was called away by the U.S. Government to work on the urgent need to increase rubber production in the Amazon Basin, Bassler left no scientific publications, but his collections have been repeatedly mined over the years and continue to provide new insight. (Bassler, ms.; Myers, 2000: 139–141).

300 mm total length, with a maximum known length of 377 mm. Following is a combined description of the 12 specimens in the type series.

PROPORTIONS AND SCUTELLATION: Head wider than high and wider than neck; eye large, its diameter greater than distance from its anterior edge to nostril in adults (relatively larger in juveniles, which have eye diameter. distance to snout tip). Body slender, slightly higher than wide, with rounded ventrolateral edges; tail slenderly tapering. Less than 400 mm total length, with tail comprising 27 % –30 % of the total. Five adult males 320–377 mm (x¯ 5 350.8 mm) total length, tail/total length 0.281 – 0.296 (x¯ 5 0.2894); two adult females 339 and 369 mm total length, tail/total 0.268, 0.271. Smallest specimen with complete tail, 160 mm total length (42 mm tail), a juvenile male with threadlike vasa deferentia and unenlarged kidney tubules. Two subadults approaching maturity at 245 mm (♀) and 259 mm (8) total length, as evidenced by enlarging ova in the female and enlarging vasa deferentia and kidney tubules in the male.

Dorsal scales smooth, in 15-15-15 rows; anal ridges lacking; a few specimens with single apical pits (situated either medially or off center) discernible on some scales, especially on neck. Ventral plates 128–139 (8 males 128–138, x¯ 5 133.3; 4 females 134–139, x¯ 5 136.8). Anal plate divided. Subcaudals in 62–70 pairs (7 males 65–70, x¯ 5 67.9; 3 females 62–66, x¯ 5 63.7).

Rostral plate wider than high, tipped forward, readily visible from above. Internasal and prefrontal plates paired, each prefrontal laterally in contact with nasal, loreal, and preocular. Supraocular large, about as long as frontal and more than half as wide. Frontal pentagonal or slightly hexagonal, about two times longer than wide, longer than distance to snout. Interparietal suture shorter than length of frontal. Loreal higher than wide, variable in shape (e.g., tipped forward and rhomboidal, or vertical and rectangular). One high, narrow preocular, rarely two preoculars (on one side only in two specimens); two postoculars, the lower one varying in size, distinctly smaller than or nearly equal to the upper. Temporals 1 + 2 in eight specimens; two other individuals with this basic pattern but having the primary and upper secondary temporals fused into one long scale; one specimen with 1 + 1 + 1/1 +1 (left/right) temporals. Eight supralabials (8/ 7 in one), with labials 2 (usually) or 2–3 touching loreal and 3–5 bordering eye. Eight, nine (usually), or rarely 10 (one with 10/9) infralabials, of which 1–4 (if only 8 infralabials) or 1–5 touch anterior genials and 4–5 or 5–6 touch posterior genials. First infralabials in contact behind mental except in one juvenile, where widely separated. Anterior and posterior genials long and narrow, subequal. Tiny, inconspicuous tubercles (presumed sensory organs) on head plates and chin.

COLOR AND PATTERN IN PRESERVATIVE: Brown or gray-brown above—gray after loss of stratum corneum—with head and neck usually darker than body for length of 9–11 scales behind parietal plates. A pair of conspicuous, black-rimmed white ocelli atop nape, occupying parts of several dorsal scales (usually not including a complete scale) just behind each parietal plate. A second pair of often conspicuous albeit incomplete ocelli situated farther back, dorsolaterally at about level of ventrals 4–5; in lateral view these markings are seen to be the expanded, rounded dorsal ends of an incomplete white collar that is medially broken by a space of several dorsal scales (fig. 2B). 4 Most of rostral plate and supralabials immaculate white, this color extending dorsad as a triangular wedge just behind each eye (a rectangular wedge in one juvenile); a black streak across tops of anterior supralabials, extending thinly under and up behind eye, then becoming wider and dropping obliquely along the white postocular wedge to lower side of neck (fig. 2B). A few specimens with a vertical white preocular bar (fig. 2B), but this region dark in most. One juvenile with an illdefined whitish blotch on frontal plate and a pair of vague whitish parietal blotches (fig. 2C).

A pair of dorsolateral lines of irregular and often vague black spots, spaced about every other scale, mainly on scale rows 6 and/or 7 on each side (fig. 1). Aforesaid dark spots not always discernible throughout body and virtually absent on some specimens (possibly due to method of preservation); often largest behind the broken collar cum ocelli on neck, where spots may fuse into vague dark crossbars that, in some juveniles, may separate vague dorsolateral pale spots (fig. 2C). A lateral line of white dashes or dots on scale row 4, sometimes weakly indicated along side of neck but more often nearly confined to rear half of body, where the pale dashes are accentuated by black pigmentation along their lower edges. Inconspicuous dorsolateral dark spots (when present) and lateral line of pale dashes extending onto tail for most of its length. Dark body color encroaching slightly onto sides of ventrals and subcaudals. Ventral surfaces immaculate pale yellow or white.

4 This feature may be geographically variable. The dorsal ends of the broken collar are narrow in the two paratypes from Ecuador —not conspicuously rounded as in the Peruvian specimens.

COLOR IN LIFE: Based on a few color notes quoted below, this is a prettily colored snake in life, with black head and nape bearing conspicuous white or yellow ocellar markings; white or yellow lips and a triangular postocular marking; ventral surfaces cream or changing from white to yellowish. Body and tail in at least one individual sea green anteriorly, then reddish brown, and grayish brown posteriorly.

Dixon and Soini (1977: 54; 1986: 115) published color notes on one or more of the three paratypes from Mishana , Peru .

Dorsum light brown with dorsolateral pair of small black spots from posterior body to tail tip; an irregular yellowish, dotted lateral line on 4th scale row, bordered below by black; venter and subcaudals cream; extreme edge of ventrals with grayish black flecks; top of head black, lips bright yellow; yellow triangular spot behind eye; pair of yellow spots behind parietals; incomplete yellow nuchal collar.

Eye color was not given, but some preserved specimens retain a pattern of a pale upper sector that is distinct from the dark lower part (fig. 2B); see also below.

Martin Henzl (letter, March 17, 1990) kindly provided the following color notes on a Peruvian specimen (NMW 31795) collected on a ridge above the Río Llullapichis, in the Serranía de Sira.

Head and nape black, upper lips white, small

white triangle laterally behind eyes, pair of

dorsolateral cream spots on occiput, another

pair of similar spots on the nape contacting the

white ventral color in a small channel. Anterior

third of body sea-green, second third of body

reddish brown, posterior third and tail grayish

brown. Indistinct dark paravertebral blotches

that soon join in a zigzag stripe becoming more

and more indistinct posteriorly; thin light lateral

stripe from midbody onto tail. Chin and

anterior third of venter white, posterior two-

thirds and underside of tail yolky yellow. Iris

dark brown with bronze blotch in upper part;

oral cavity greyish, tongue dark with pink tips.

HEMIPENIS

RETRACTED ORGAN OF EUTRACHELOPHIS BASSLERI : The following description is based on the uneverted left hemipenis of AMNH

R-55786, which was opened by midventral incision and then removed and pinned flat for illustration (fig. 3A). Data also were taken from the uneverted right organ of TCWC 41424, which was examined in situ.

Major retractor muscle originating at level of subcaudals 27 or 28, and anteriorly inserting without division on end of single (unbifurcated) hemipenis at level of subcaudals 10 or 12. The distal fourth of the uneverted organ (fig. 3A) is a nude area of folded tissue—the proximal part of this area being somewhat puckered and the whole region apparently capable of considerable expansion. The midsection (about 40 % of length of organ) is densely spinulate and less folded than the distal fourth, although the area between the branches of the sulcus spermaticus appears capable of greater expansion than the rest of the midsection. There is a densely spiculate section around the proximal part of the otherwise distal nude section. There are roughly 30 large to very small spines from the basal region distad into the densely spiculate area. 5 The extreme base of the organ (proximal 10 %) is nearly nude, with only a few spinules. There are no basal spines obviously enlarged compared with the others and no basal naked pocket (sensu Myers, 1974: 32). The deeply incised sulcus spermaticus divides low on the organ and its branches terminate abruptly about two-thirds of the way onto the distal nude section. The sulcus lies mostly on the lateral wall of the uneverted organ (fig. 3A).

EVERTED ORGAN OF EUTRACHELOPHIS BASSLERI : The right hemipenis of AMNH R-25193 (paratype) was manually everted by Myers in the late 1970s, using the ‘‘Waite Gibson Technique’’ later described in Myers and Cadle (2003: 299). The distal nude section (fig. 3A) everted as a domelike head or capitulum that lacks a free overhanging edge (fig. 3B–D). The dome is nude, except for branches of the sulcus spermaticus and except proximally, where it is densely spiculate as seen in the retracted organ (fig. 3A). Owing to differential tissue expansion, the

5 Tiny, usually mineralized, hemipenial spines are commonly called ‘‘spinules,’’ but spicules and spiculate seem to be more appropriate terms for these even tinier structures that also are mineralized (they can be ‘‘felt’’ with a very fine teasing needle and transiently stained with Lugol’s iodine solution).

sulcus branches acquired a centrifugal orientation upon hemipenial eversion, entering onto the bulbous dome nearly from opposite sides of the organ (see figs. 3B, D). There are no greatly enlarged spines, only relatively large spines that are positioned laterally and basally, with numerous small spines or spinules on the sulcate and asulcate sides of the hemipenial body (fig. 3B,C).

The left organ of TCWC 41424 had been manually turned inside out prior to our examination, and, although the base had been torn in the process, it was possible to tie off and temporarily inflate the distal half (see views in fig. 3D). This partly everted hemipenis appears to have the apical nude dome fully expanded, although manually everted organs often do not retain their original elasticity (Myers and Cadle, 2003: 295, 300).

SKULL AND DENTITION: The skull was removed from AMNH R-55786. See figure 10 and text under Global Comparisons. Ten maxillae in 10 specimens bear 26–29 (x¯ 5 27.3) small, subequal teeth, followed by a distinct diastema and two ungrooved fangs, the last fang slightly offset laterad. The maxillary fangs are about twice as large as the prediastemal teeth and are further differentiated by having knifelike rear edges. AMNH R-55786 has 19 palatine teeth, followed by about 30–31 pterygoid teeth; 34 dentary teeth. The holotype has 32 (right) or 34 (left) dentary teeth on the previously excised mandibles.

VERTEBRAE, HEAD MUSCLES, GLANDS, AND VISCERA: See under Global Comparisons.

REMARKS

The general location of Bassler’s ‘‘Pisqui Hills’’—the type locality of Eutrachelophis bassleri —can be determined from an unpublished report (Bassler, MS.). Bassler first explored and mapped the Río Pisqui in 1923, traveling 186 km by river from its mouth (149 m elev.) to the head of canoe navigation (259 m), followed by an additional 18 km on foot beyond the first cataracts— a straight-line distance of 93 km by Bassler’s careful reckoning. He determined latitude and longitude as 7 ° 429 S, 75 ° 009 W at the mouth of the Río Pisqui and as 8 ° 229 S, 75 ° 309 W at the end of his traverse; it may be noted that the first set of coordinates agrees within a few minutes to recent maps and gazetteers. Bassler described the first 45 km (by river) as ‘‘a flood plain subject for the greater part to a period of inundation each year and the channel here is not permanent for lateral erosion is active.’’ Upriver, ‘‘this recent flood plain merges into a plain determined by firmer though still practically unconsolidated sediments and here the channel is deeper and appears to change very little even over long periods of time.’’ Somewhere on this upper plain Bassler wrote that,

hills 200 ft. high were observed but between these and the mountains [to westward] the hills are usually under 100 ft in altitude above the general level of the plain. Beyond the plain the mountains [evidently the northern end of Cordillera Azul, an Andean front range] rise abruptly with stupendous cliffs and a very rugged skyline, with relief of 3000 ft. or more.

The 200 ft-high (60 m) hills on the higher flood plain of the upper Río Pisqui must certainly be what Bassler gave as ‘‘Pisqui Hills’’ for specimens collected on this and subsequent trips, and the locality can with confidence be placed within the area bounded by parallels 8 ° 009–8 ° 229 S and meridians 75 ° 309–75 ° 509 W.

Figures

Fig. 1. Eutrachelophis bassleri, new species. Dorsal and ventral views of adult specimens: A. AMNH R- 52926 (male holotype), from upper Río Pisqui, Peru. B. AMNH R-53473 (female paratype), from upper Río Utuquinia, Peru, near border with Brazil. The conspicuous nuchal markings are ‘‘cream’’ or ‘‘yellow’’ in life. Specimens shown life size.

Fig. 2. Heads of Eutrachelophis bassleri, new species. A, B. AMNH R-53473, adult female (369 mm total length), in dorsal and lateral view, ×3.9. C. TCWC 41425, juvenile male (160 mm total length), ×2.5. In addition to the white or yellow nuchal markings, the postocular extension of white or yellow labial color (B) is diagnostic of E. bassleri and its unnamed sister species (cf. fig. 4); the white preocular bar is present or absent in E. bassleri.

Fig. 3. Hemipenes of Eutrachelophis bassleri, new species. The distal nude section is greatly distensible, becoming hemispherical on eversion. Because of differential tissue expansion, the close-lying branches of the sulcus spermaticus diverge and acquire a centrifugal orientation, entering onto the nude dome from nearly opposite sides of the everted organ. A. Uneverted left hemipenis of AMNH R-55786 (paratype), opened by midventral incision. B. Everted right hemipenis in sulcate view, AMNH R-25193 (paratype; depiction of the manually everted organ). C. Same organ as in B, in asulcate view. D. Distal half of everted hemipenis showing appearance of the maximally inflated, mostly nude dome, from left to right: asulcate side, apex, and sulcate side. Left organ of TCWC 41424, paratype. (This organ previously had been manually turned inside out, but, because the base had been badly damaged, only the distal half was tied off and injected with petroleum jelly in an attempt to determine maximum inflation). Abbreviations: Folds, expansion folds; Mus, major retractor muscle; ND, nude dome; SB, a branch of the sulcus spermaticus; SS, sulcus spermaticus (proximal to bifurcation); Spic, densely spiculate area below and around base of nude dome; SpLg, large lateral and basal spines; SpSm, small spines on sulcate and asulcate faces.