Wednesday, December 23, 2020

[Herpetology • 2021] A Phantom on the Trees: Integrative Taxonomy Supports A Reappraisal of Rear-fanged Snakes Classification (Dipsadidae: Philodryadini)

Chlorosoma dunupyana 
Melo-Sampaio, Passos, Martins, Jennings, Moura-Leite, ... et Souza, 2021

photo: Germán Chávez
The Neotropics harbour a spectacular amount of biodiversity, but many of these species remain to be discovered and placed into the tree of life. In the neotropical snake genus Philodryas, the systematics of these rear-fanged snakes has been controversial and debated in recent years. Here, we combine published datasets with new morphological (scale microdermatoglyphics, osteology, pholidosis and genital features) and molecular (mitochondrial and nuclear) data to reassess the phylogenetic positioning of rear-fanged snakes within the tribe Philodryadini. We identified putative synapomorphies and pronounced morphological variation in hemipenial features. Our results suggested a need to reclassify many species in order to clarify some relationships within the Philodryas radiation. We also redefined Philodryadini by resurrecting three genera and naming a newly discovered species.

Keywords: Male genitalia, Microdematoglyphics of dorsal scales, Molecular phylogeny, Osteology, Philodryadinii systematics, Soft anatomy

Fig. 1. Phylogenetic relationships of Xenodontinae snakes estimated under a Bayesian framework based on six genes. Posterior probabilities and bootstrap values are separated by slash respectively. Clade A: Philodryas; Clade B: Chlorosoma viridissimum + C. laticeps and C. dunupyana; Clade C: Xenoxybelis; Clade D Pseudablabes; Clade E: Tropidodryadini; Clade F: Philodryadini.
Order Squamata Oppel, 1811

Family Dipsadidae Bonaparte, 1838
Subfamily Xenodontinae Bonaparte, 1838

  Genus Pseudablabes Boulenger, 1896 status revalidated

Pseudablabes agassizii (Jan, 1863)
Pseudablabes patagoniensis (Girard, 1858) comb. nov. 

We tentatively include Pseudablabes arnaldoi (Amaral, 1932) comb. nov. in this genus based on overall external similarities (e.g., colour pattern, pholidosis and general habitus), but mainly by sharing unique similarities of hemipenial morphology (Fig. 2).

Fig. 3. Live specimens of Chlorosoma:
 Chlorosoma laticeps [Photo: Arthur Abegg] 
& C. viridissimum (UFAC-RB 359) from Rio Branco, Acre, Brazil.

 Genus Chlorosoma Wagler, 1830 status revalidated
Chlorosoma viridissimum (Linnaeus, 1758)
Chlorosoma laticeps (Werner, 1900) comb. nov.

 Genus Xenoxybelis Machado, 1993 status revalidated

Xenoxybelis argenteus (Daudin, 1803) 
Xenoxybelis boulengeri (Procter, 1923)

Chlorosoma dunupyana sp. nov., Adult male paratype (CORBIDI 19094).

Fig. 8. Dorsal (A), lateral (B) and ventral views (C) of the holotype of Chlorosoma dunupyana sp. nov. (UFAC-RB 345) from Parque Zoobotânico, Rio Branco, Acre, Brazil.

Chlorosoma dunupyana sp. nov. 
Taeniophallus brevirostris
(non Peters 1863) Silva et al., 2012:169.

 Etymology: From the Panoan speakers Katukina/Kashinawa Indigenous words dunu (= snake) + pyanã (= venomous) (see Souza et al. 2002), used herein in reference to well-developed Duvernoy’s gland and rear-fang in the posterior portion of maxillary of the newly discovered snake.

Paulo R. Melo-Sampaio, Paulo Passos, Angele R. Martins, W. Bryan Jennings, Julio C. Moura-Leite, Sérgio A. A. Morato, Pablo J. Venegas, Germán Chávez, Nathocley M. Venâncio and Moisés B. Souza. 2021. A Phantom on the Trees: Integrative Taxonomy Supports A Reappraisal of Rear-fanged Snakes Classification (Dipsadidae: Philodryadini).  Zoologischer Anzeiger.  290; 19-39. DOI: 10.1016/j.jcz.2020.10.008