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Dipsas incerta (JAN, 1863)

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Higher TaxaColubridae (Dipsadinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common NamesE: Jan's Snail-eater 
SynonymLeptognathus incertus JAN 1863: 101
Dipsas incerta — PARKER 1935
Dipsas incerta — PETERS & OREJAS-MIRANDA 1970: 86
Dipsas incerta — PASSOS et al. 2004
Dipsas incerta — WALLACH et al. 2014: 232 
DistributionFrench Guiana, Suriname, Guiana, Brazil (Roraima fide Costa & Bérnils 2018)

Type locality: “Gujana francese” (= French Guiana) but this record was disputed by Peters (1960).  
TypesHolotype: lost; originally MSNM (Milano), Department of Ornithology of the Museo Civico di Storia Naturale, Milano, Italy but destroyed during the Second World War (PASSOS et al. 2004). Neotype: BMNH 1946.1.21.4 (formerly, adult male, SVL 435 mm, TL 215 mm, obtained from the collection of Dr. Van Lidth de Jeude, Surinam (neotype designation by Passos 2004 invalid fide Harvey 2008). 
DiagnosisDescription: Peters 1960: 127ff 
CommentSynonymy: Leptognathus alternans FISCHER 1885 has been removed from the synonymy of D. incerta by PASSOS et al. (2004). D. copei has been synonymized with D. incerta by PASSOS et al. 2004 and revalidated by HARVEY 2008. The neotype designated by PASSOS et al. (2004) is invalid fide HARVEY 2008.

Characters: According to Jan (1863) and Jan and Sordelli (1870), the holotype of L. incertus possesses 15 dorsal scales rows, vertebral row approximately twice as large as adjacent scales; loreal enters the orbit; 1 preocular; 2 postoculars; no subocular; temporals 2 + 3 + 2; 9 supralabials, fourth to sixth in contact with the orbit; infralabials 10 on both sides, first pair in contact behind the symphisial; first to fifth pair touch the first pair of genials; fifth and sixth touch the second pair of genials; number of pairs of genials 3 or 4.

Boulenger (1896) provided a key to the species of the genus Leptognathus. According to this key, L. alternans and L. incertus differ in the number of ventrals, subcaudals, and preocular scales. Leptognathus alternans (male; n = 1) has 197 ventrals, 110 subcaudals, and 2 preoculars scales, while L. incertus (male; n = 1) has 204 ventrals, 122 subcaudals, and 1 preocular scale. The specimen of L. alternans examined by Boulenger (1896) was the holotype, while the specimen associated with L. incertus was from São José dos Campos, State of São Paulo. The colour patterns described by Boulenger (1896) for these two specimens are quite similar, the differences being easily acceptable as falling within normal intraspecific variation. The same interpretation can be used to justify the differences in the pholidosis of the specimens.

Distribution: not in Venezuela (Luis Esqueda, pers. comm., 21 April 2016, see also Natera-Mumaw et al. 2015). Not in Brazil fide Nogueira et al. 2019 (Atlas), where it is replaced by D. copei (C. Nogueira & Paulo Passos, pers. comm., 13 May 2020). Some older sources reported it from Espirito Santo to Santa Catarina; Rio Grande do Sul, Rio de Janeiro.

Habitat: fully arboreal (Harrington et al. 2018).

Group: the D. incerta species group (sensu Harvey, 2008; Fernandes et al., 2010, Mebert et al. 2020) currently includes D. sazimai, D. alternans, and D. incerta. 
  • Boulenger, G.A. 1896. Catalogue of the snakes in the British Museum, Vol. 3. London (Taylor & Francis), xiv + 727 pp. - get paper here
  • Claessen, H. 2003. Slangen van de Guyana’s. Deel V. Lacerta 61 (4): 123-133 - get paper here
  • Costa, Henrique Caldeira; Renato Silveira Bérnils 2018. Répteis do Brasil e suas Unidades Federativas: Lista de espécies. Herpetologia Brasileira 7 (1): 11-57
  • Fischer, J. G. 1885. Ichthyologische und herpetologische Bemerkungen. V. Herpetologische Bemerkungen. Jahrb. Hamburg. Wiss. Anst. 2: 82-121 - get paper here
  • Günther,A. 1872. Seventh account of new species of snakes in the collection of the British Museum. Ann. Mag. Nat. Hist. (4) 9: 13-37 - 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
  • Harvey, Michael B.; Gilson Rivas Fuenmayor, José Rances Caicedo-Portilla, and José Vicente Rueda-Almonacid 2009. Systematics of the Enigmatic Dipsadine Snake Tropidodipsas perijanensis Alemán (Serpentes: Colubridae) and Review of Morphological Characters of Dipsadini. Herpetological Monographs 22 (1): 106-132 - get paper here
  • Jan, G. 1863. Elenco Sistematico degli Ofidi descriti e disegnati per l'Iconografia Generale. Milano, A. Lombardi. vii + 143 pp. - get paper here
  • Kornacker,P.M. 1999. Checklist and key to the snakes of Venezuela. PaKo-Verlag, Rheinbach, Germany, 270 pp.
  • Lancini,A.R. & Kornacker,P.M. 1989. Die Schlangen von Venezuela. Armitano Editores C.A., Caracas, 1-381
  • Mebert K., Passos P., Fernandes D.S., Entiauspe-Neto O.M., Alvez F.Q., Machado A.S., Lopes R.T. 2020. A new species of snail-eating snake, Dipsas Cope, 1860 (Serpentes: Colubridae: Dipsadinae), from the Atlantic Forest of Brazil. South American Journal of Herpetology 17 (1): 43–62 - get paper here
  • Parker, H. W. 1935. The frogs, lizards, and snakes of British Guiana. Proc. Zool. Soc. London 1935: 505-530 - get paper here
  • Passos, P., D. S. Fernandes and U. Caramaschi 2004. The taxonomic status of Leptognathus incertus Jan, 1863, with revalidation of Dipsas alternans (Fischer, 1885) (Colubridae: Dipsadinae). Amphibia-Reptilia 25 (4): 381-393 - 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
  • Starace, Fausto 1997. Contribution to the study of the snakes of French Guyana II. The presence of Dipsas copei (Gunther, 1872) in French Guyana. Litteratura Serpentium 17 (5): 97-101, 18 (4): 104 (erratum)
  • Starace, Fausto 1998. Guide des Serpents et Amphisbènes de Guyane. IBIS Rouge Editions, Guadeloupe, Guyane, 450 pp.
  • Starace, Fausto 2013. Guide des Serpents et Amphisbènes de Guyane. Ibis Rouge Editions, Matoury, Guyane, ISBN 978-2-84450-407-4 - get paper here
  • Vidal, Nicolas; de Massary, Jean-Christophe; Marty, Christian 1998. Nouvelles especes de serpents pour la Guyane francaise. Revue Française d'Aquariologie Herpétologie 25 (3-4): 131-134 - 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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