A new genus for the snake Erythrolamprus problematicus

Arcanumophis problematicus from Santo Domingo, Peru.
Photographs by A. Catenazzi.
The snake Liophis problematicus was described as a new species by Myers in 1986. The holotype was collected at 1520 m on the Amazonian side of the Andes in the Department of Puno in extreme southeastern Peru. This is a very small snake, an adult male that had a total length of 275 mm total length. It has a bilobed hemipenis with nude apical discs, a condition defining the tribe Xenodontini with about six genera of Neotropical xenodontine colubrids. Like other Liophis is did have the ability to flatten the anterior body to form a narrow hood-like appearance. Myers could not say much else about the relationship of this snake to others and assigned it to the genus Liophis. When Grazziotin et al (2012) placed all members os the genus Liophis in Erythrolamprous it became E. problematicus.

During a field expedition to an abandoned mine at Santo Domingo, on 8 June 2016, in the upper reaches of a tributary of the Inambari River near Paco Pacuni, Department of Puno, Peru Smaga et al. (2019) collected a snake identified as the second specimen of E. problematicus. Based on new data recovered from this specimen, Smaga et al. conducted a molecular phylogenetic analysis of Xenodontini with 29 terminals in the tribe, including partial sequences of mitochondrial markers 12S and 16S rRNA of E. problematicus. Their results reject the allocation of the species to Erythrolamprus, recovering it as the sister group of all other members of the tribe.

Morphologically, the snake is unique. A crease on the rostral scale could reflect semi-fossorial habits but the snake shows no other morphological traits commonly found in fossorial snakes. The new specimen was found in the soil below layers of mosses, further supporting the idea that this snake is semi-fossorial, but other anatomical characteristics of the snake (skull morphology and large eyes), do not support a semi-fossorial hypothesis. The authors placed this snake in the new genus Arcanumophis.


References 
Grazziotin, Felipe G.; Hussam Zaher, Robert W. Murphy, Gustavo Scrocchi, Marco A. Benavides, Ya-Ping Zhang and Sandro L. Bonatto 2012. Molecular phylogeny of the New World Dipsadidae (Serpentes: Colubroidea): a reappraisal. Cladistics DOI: 10.1111/j.1096-0031.2012.00393.x

Myers, C W 1986. An enigmatic new snake from the Peruvian Andes, with notes on the Xenodontini (Colubridae: Xenodontinae). American Museum Novitates (2853): 1-12.

Smaga CR, Ttito A, Catenazzi A. Arcanumophis, a new genus and generic allocation for Erythrolamprus problematicus (Myers 1986), Xenodontinae (Colubridae) from the Cordillera de Carabaya, southern Peru. Zootaxa. 2019 Sep 16;4671(1):129-38.

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