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Dipsas nicholsi (DUNN, 1933)

IUCN Red List - Dipsas nicholsi - Least Concern, LC

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Higher TaxaColubridae (Dipsadinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common Names 
SynonymSibynomorphus nicholsi DUNN 1933: 193
Sibon nicholsi — DUNN 1940
Dipsas nicholsi — SMITH 1958
Dipsas variegata nicholsi — PETERS 1960: 137
Dipsas variegata — PETERS & OREJAS-MIRANDA 1970: 90
Dipsas nicholsi — CADLE & MYERS 2003
Dipsas nicholsi — WALLACH et al. 2014: 233 
DistributionC Panama (endemic)

Type locality: Chagres River and Pequeni River, Panama [i.e. the junction of the Río Pequení with the Río Boquerón in the ‘‘mid-basin’’ [= upper drainage] of the Río Chagres at approximately 9° 21’N, 79° 33’ W].  
TypesHolotype: MCZ 37884 (head and neck only) 
DiagnosisDiagnosis: Dipsas nicholsi is a pale brown snake with distinctive contrasting patterns on the head and dorsum. The head is relatively unmarked except for a bold blackish brown n-shaped marking extending from the anterior edge of the frontal or frontal/prefrontal sutures to the neck, where the branches are confluent with a pair of elongate dorsolateral blotches. Apart from the dorsal head marking and occasional narrowly darkened sutures, the head is unmarked. The blotches on the dorsum are black or blackish brown, strongly elliptical or oval and much broader than tall, and have a variably distinct narrow pale border. The interspaces are slightly broader than the blotches for the length of the body. Additional blackish streaks or irregular spots are sometimes present between the blotches. These pattern characteristics, particularly the form of the dorsal head marking and the dorsal blotches (including pale border), are constant in all specimens of D. nicholsi we have examined. Dipsas nicholsi has a relatively high number of ventrals (males 198–208, one female 200) and subcaudals (males 92–98, one female 95). However, scale characters overlap greatly among species of Dipsas and should not be used exclusively for identifications. The color pattern seems to be the most constant and readily diagnostic feature, as noted by Dunn (1933). No other known species of Dipsas from Panama or western Colombia and Ecuador, with the exception of D. andiana, has the distinctive head marking present in D. nicholsi. Dipsas nicholsi is very similar in color pattern and scutellation to D. andiana from western Ecuador [from CADLE & MYERS 2003]. 
CommentSnail-eater. Previously considered as subspecies or synonym of Dipsas variegata. Specimens from western Ecuador previously assigned to ‘‘Dipsas variegata nicholsi’’ represent a different species—Dipsas andiana (Boulenger),
which has been resurrected from the synonymy of Dipsas oreas (Cope) by CADLE & MYERS (2003).

Habitat: fully arboreal (Harrington et al. 2018). 
EtymologyNamed after John Treadwell Nichols (1883-1958), an ichthyologist and ornithologist who co-described the rediscovered Bermuda Petrel (1916), believed extinct since the 1620s. He founded Copeia (1913), which became the official journal of the American Society of Ichthyologists and Herpetologists (1923). 
  • Beolens, Bo; Michael Watkins, and Michael Grayson 2011. The Eponym Dictionary of Reptiles. Johns Hopkins University Press, Baltimore, USA - get paper here
  • Cadle, J.E. & Myers, C.W. 2003. Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae). American Museum Novitates 3409: 1-47 - get paper here
  • Dunn, E.R. 1933. A new snake from Panama. Copeia 1933 (4): 193-194 - get paper here
  • Dunn,E.R. 1940. New and noteworthy herpetological material from Panamá. Proc. Acad. Nat. Sci. Philadelphia. 92: 105-122. - get paper here
  • Harrington, Sean M; Jordyn M de Haan, Lindsey Shapiro, Sara Ruane 2018. Habits and characteristics of arboreal snakes worldwide: arboreality constrains body size but does not affect lineage diversification. Biological Journal of the Linnean Society 125 (1): 61–71 - get paper here
  • Myers, Charles W.; Iba�nez D., Roberto.; Cadle, John E. 2007. On the uniquely fragmented distribution of a rare Panamanian snake, Dipsas nicholsi (Colubridae, Dipsadinae). American Museum novitates (3554) - get paper here
  • Peters , J. A. 1960. The snakes of the subfamily Dipsadinae. Misc. Publ. Mus. Zool., Univ. Michigan (114): 224 pp. - get paper here
  • Ray JM, Sánchez-Martínez P, Batista A, Mulcahy DG, Sheehy III CM, Smith EN, Pyron RA, Arteaga A 2023. A new species of Dipsas (Serpentes, Dipsadidae) from central Panama. ZooKeys 1145: 131–167
  • Ray, Julie M. and Patty Ruback 2015. Updated checklists of snakes for the provinces of Panamá and Panamá Oeste, Republic of Panama. Mesoamerican Herpetology 2 (2): 168-188 - get paper here
  • Ray, Julie M.; Chad E. Montgomery, Heidi K. Mahon, Alan H. Savitzky, and Karen R. Lips 2012. Goo-Eaters: Diets of the Neotropical Snakes Dipsas and Sibon in Central Panama. Copeia 2012 (2): 197-202. - get paper here
  • Smith, H.M. 1958. Handlist of the snakes of Panamá. Herpetologica 14: 222-224. - 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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