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Tachymenis affinis BOULENGER, 1896

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Higher TaxaColubridae (Dipsadinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common NamesE: Boulenger's Slender Snake 
SynonymTachymenis affinis BOULENGER 1896: 119
Tachymenis affinis — WALKER 1945: 22
Tachymenis affinis — PETERS & OREJAS-MIRANDA 1970: 289
Tachymenis affinis — LEHR 2002: 96
Tachymenis affinis — WALLACH et al. 2014: 695 
DistributionPeru (Huánuco, Amazonas)

Type locality: Muña, Peru  
TypesHolotype: BMNH 1946.1.2.80 
DiagnosisDiagnosis: “It is a Tachymenis differing from all other members of the genus in having a dorsal scale reduction pattern of 17-17-15 instead of 19-19-15. It further differs from peruviana in having a reduced color pattern, but resembles it so much in other features that it has been included in the peruviana complex.” (Walker 1945: 22)

Description. T. affinis is similar to peruviana in body form, penial characters, and general dental pattern. The specimen in question has 9 solid maxillary teeth that are subequal in size and are followed after a gap by a pair of enlarged grooved fangs. The type had 15 solid maxillary teeth. This may seem like a great discrepancy, but the maxillary range in peruviana is at least 5-10.
The cephalic plates of the specimen examined are quite similar to those of peruviana except that the frontal is only 1Pi times as long as broad, and is shorter than the parietals. The nasal is semidivided. There is 1 preocular; 2 postoculars; temporals 2-2 on the right side, shrivelled on the left; supralabials 8(4-5); infralabials 9(5). The cephalic plates in the type were essentially the same. Its temporals were 2-3.
The dorsal scales are smooth, have single apical pits, and a reduction pattern of 17-17-15. The abdominals are rounded, 147; anal divided; caudals 50, 6 of these are single and the rest paired; total ventrals 197. The type, also a male, had 153 abdominals, 57 caudals, and 210 total ventrals.
As can be seen, the specimen of affinis from Macchu Picchu agrees very well with the type in the above characters, but it does differ a bit in coloration. Both are brownish above, but the dorsal scales are darker than the lateral ones in the Macchu Picchu specimen (fig. 12) while the lateral scales are said to be darker in the type. However, I do not believe that this is too significant for the color pattern of·both specimens seems to have been derived from a condition similar to that in peruviana by a process of reduction of the prominent dark stripes and spots. Both specimens have fair remnants of the head markings of peruviana. The type has traces of the rows of dark dorsal spots. These are obscure in the Macchu Picchu specimen, but traces of the light middorsal line can be seen. Both lack the black apical dots that are so prominent in the dorsal scales of peruviana. The ventral scales of the Macchu Picchu specimen are darker than in the type (Walker 1945: 22).

Size: The snake examined has a total length of 454 mm.; tail 84 mm.; ratio of tail length to total length 0.18. The type was a bit larger, and had a ratio of 0.21 (Walker 1945: 23). 

Walker (1945: 22) suggests that the type locality is on upper Río Huallaga, Huanuco, Peru. 
  • Boulenger, G.A. 1896. Catalogue of the snakes in the British Museum, Vol. 3. London (Taylor & Francis), xiv + 727 pp. - get paper here
  • Chávez, Germán 2011. Tachymenis affinis Boulenger, 1896 (Squamata: Colubridae): distribution extension in Perú. Herpetotropicos 7 (1-2): - get paper here
  • Lehr, E. 2002. Amphibien und Reptilien in Peru. Natur und Tier-Verlag (Münster), 208 pp. - get paper here
  • Walker, W.F. 1945. A Study of the Snake, Tachymenis peruviana Wiegmann AND ITS Allies. Bull. Mus. Comp. Zool. Harvard 96: 1-56 - get paper here
  • Wallach, Van; Kenneth L. Williams , Jeff Boundy 2014. Snakes of the World: A Catalogue of Living and Extinct Species. [type catalogue] Taylor and Francis, CRC Press, 1237 pp.
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