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Eutrachelophis bassleri MYERS & MCDOWELL, 2014

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Higher TaxaColubridae (Dipsadinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common Names 
SynonymEutrachelophis bassleri MYERS & MCDOWELL 2014
Eutrachelophis bassleri — ZAHER & PRUDENTE 2019 
DistributionPeru (Loreto), Ecuador

Type locality: Pisqui Hills, [upper] Río Pisqui, Province of Loreto  
TypesHolotype: AMNH 52926, an adult male, 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°22’ S, 75°30–75°50’ 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 52682 (H. Bassler, date?); Serranía de Sira, ridge above R ́ıo Llullapichis, 510 m (9°29’ S, 74°49’W), 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, R ́ıo Cushabatay, AMNH 55786 (H. Bassler, Sept. 1927);2 Pebas, Río Ampiyacu, 250 ft., AMNH 25193 (collector?); Río Tapiche, AMNH 52441 (H. Bassler, Jan. 1928); upper Río Utuquinia, AMNH 53473 (H. Bassler, Feb. 1928). 
DiagnosisDIAGNOSIS (genus): Small terrestrial colubrids lacking hypapophyses (hemal keel present) on posterior trunk vertebrae. High number (about 25–30) of prediastemal maxillary teeth followed by diastema and two enlarged, ungrooved teeth (the last offset laterad1); differentiated rear maxillary teeth not accompanied by correspondingly conspicuous differentiation of Duvernoy’s gland. Spiny hemipenis either divided, with spines to apices of lobes, or single with distal nude area; hemipenis lacking calyces, flounces, or apical discs; sulcus spermaticus forked proximally, with branches centrifugal (at least when organ is everted). Eye large, with round pupil. Habitus slender, with smooth dorsal scales in 15-15-15 rows; single scale pits present or absent; no anal ridges. Normal complement of colubrid head plates; < 150 ventrals; anal plate divided, > 90 subcaudals, paired. Color pattern with black-rimmed pale ocelli or elongated spots on head or on head and neck; dorsum with dark stripes or spots anteriorly, becoming nearly uniform posteriorly.
The above combination of traits is unique. Externally, the species of Eutrachelophis are readily differentiated from most other New World snakes by the combination of 15 dorsal scale rows and the presence of conspicuous ocellar markings on head or on head and neck. There may be a vague resemblance in pattern with some specimens of the variable Taeniophallus occipitalis, which also has 15 scale rows, but occipitalis differs in having a white canthal line (fig. 15B in Myers & McDowell 2014), more ventrals (> 160), fewer maxillary teeth (about 13–17 + 2), and a calyculate hemipenis.

Diagnosis (genus): Eutrachelophis can be distinguished from the other genera of Xenodontini by the combination of the following characters: partial overlap between the edges of the fenestra ovalis and mandibular trigeminal foramen on the prootic; 15 dorsal scale rows; less than 150 ventrals; cloacal plate divided; less than 90 subcaudals; unilobed hemipenis with large apical disks contacting each other on the midline; presence of a single expanded ocellus or two pairs of ocelli on the nape behind the parietal scales and a second less defined pair of ocelli on the neck region; presence of a postocular wedge of pale color extending dorsally from the lip; and dorsum with dark stripes or spots anteriorly, becoming nearly uniform posteriorly (Zaher & Prudente 2019).

Diagnosis. Eutrachelophis bassleri is distinguished from all other species by the following combination of characters: 15-15-15 number of dorsal scale rows; 8 supralabials, 2nd and 3rd contacting loreal and 3rd to 5th bordering
eyes; 8-9 infralabials, 1st to 4th or 1st to 5th contacting anterior chinshields and 4th and 5th or 5th and 6th posterior chinshields; 128-139 ventrals; 62-70 subcaudals; 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; hemipenis slightly bilobed with apical disks; and mean of 27.4 maxillary teeth subequal in size and recurved, followed by diastema and two ungrooved fangs (Myers and McDowell, 2014) (Zaher & Prudente 2019).

Comparisons. Eutrachelophis bassleri differs from Eu. papilio by having a pair of blackrimmed white ocelli on the nape (vs. a single laterally expanded, butterfly-shaped, blackrimmed white ocelli in Eu. papilio), lower number of ventrals (128-139 vs 139-145 in Eu. papilio), and shorter hemipenial lobe that is rounded distally (longer hemipenial lobe tapering distally in Eu. papilio) (Zaher & Prudente 2019). 
CommentType species: Eutrachelophis bassleri MYERS & MCDOWELL 2014 is the type species of the genus Eutrachelophis MYERS & MCDOWELL 2014.

Synonymy: Zaher & Prudente 2019 consider the tribe Eutrachelophiini Myers and McDowell, 2014 as a junior synonym of the tribe Xenodontini. 
EtymologyETYMOLOGY: The intended meaning of the generic name is ‘‘beautiful-necked snake.’’ It is compounded from the prefix eu- (beautiful) + trachelos (neck) + ophis (a serpent), all from the Greek. Gender masculine.

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 zoological and ethnographic collecting in eastern Peru. 
  • Echevarría, Lourdes Y. and Pablo J. Venegas. 2015. Eutrachelophis bassleri coloration and photographs in life. Herpetological Review 46 (3): 449 - get paper here
  • Gemel, R.; G. Gassner & S. Schweiger 2019. Katalog der Typen der Herpetologischen Sammlung des Naturhistorischen Museums Wien – 2018. Ann. Naturhist. Mus. Wien, B 121: 33–248
  • Myers, Charles W. and Samuel B. McDowell 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 385 (1) : 1-112. - get paper here
  • Torres-Carvajal O, Pazmiño-Otamendi G, Salazar-Valenzuela D. 2019. Reptiles of Ecuador: a resource-rich portal, with a dynamic checklist and photographic guides. Amphibian & Reptile Conservation 13 (1): [General Section]: 209–229 (e178) - get paper here
  • Zaher, Hussam and Ana L.C. Prudente 2019. The enigmatic Amazonian genus Eutrachelophis: morphological evidence and description of new taxa (Serpentes: Dipsadidae: Xenodontini). Amphibia-Reptilia 41: 215-231 - get paper here
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