Taxonomic Notes on the Genus Siagonodon Peters, 1881, with a Report on Morphological Variation in Siagonodon cupinensis (Bailey and Carvalho, 1946) (Serpentes: Leptotyphlopidae)
The family Leptotyphlopidae comprises about 120 species allocated in 12 genera including Siagonodon, the latter with four currently recognized species. Here we propose new diagnostic characters for the genus Siagonodon based on the analysis of variation of external morphology and comparisons with related taxa. In order to evaluate the diagnostic characters of the genus Siagonodon, representatives of other genera of the tribe Epictini occurring in South America were also analyzed (Epictia, Rena, and Trilepida). We examined 14 species of the family Leptotyphlopidae and analyzed 67 characters of external morphology. We propose six new diagnostic characters for the genus Siagonodon, including: rostral scale with enlarged base, terminal spine reduced or absent, and straight snout in lateral view. Furthermore, we provide new data on morphological variation and geographical distribution of the poorly known Siagonodon cupinensis, expanding the diagnosis of this taxon and improving comparisons with congeners.
Geographic distribution of the genus Siagonodon. Stars: Siagonodon cupinensis (analyzed data). White star represents the type locality of S. cupinensis, and the black star with a white circle symbolizes the doubtful locality of this species; squares: Siagonodon septemstriatus (analyzed data); triangles: Siagonodon acutirostris (analyzed data); circle: Siagonodon borrichianus. The black circle represents analyzed data of S. borrichianus, and the white circle represents literature data of this species.
Comparisons of the lateral portion of the head of a representative of Siagonodon and other Neotropical genera. The arrows display the (A) straight snout of Siagonodon cupinensis, UFMT 5611; (B) truncate snout of Trilepida koppesi, MNRJ 11206; and (C) rounded snout of Epictia munoai, MNRJ 20369.
Comparisons of the dorsal portion of the head of a representative of Siagonodon and other Neotropical genera. The vertical lines display the (A) enlarged rostral base in Siagonodon cupinensis, UFMT 5611; narrow rostral base in (B) Trilepida koppesi, MNRJ 11206 and (C) Epictia munoai, MNRJ 20369.
Comparisons of the caudal spine of a representative of Siagonodon and other Neotropical genera. The arrows display the (A) conspicuously reduced caudal spine of Siagonodon cupinensis, UFMT 5611; enlarged caudal spine of (B) Trilepida koppesi, MNRJ 11206 and (C) Epictia munoai, MNRJ 20369.
The holotype of Siagonodon cupinensis, MNRJ 387. (A) Dorsal, (B) lateral, and (C) ventral views.
Contributor Notes
Associate Editor: B. Stuart.