Phylogenetic and osteological assessment of specimens assigned to Siphonops hardyi (Gymnophiona: Siphonopidae), with the description of a new species from Rio de Janeiro, Brazil

We studied the systematics of the second most species-rich family of caecilian amphibians from the Neotropical region, with a focus on specimens assigned to Siphonops hardyi from the Brazilian Atlantic Forest. Our study combined molecular phylogenetic analysis with comparative osteology of crania to investigate the interspecific relationships within Siphonopidae. We found: (i) a paraphyly of the genus Siphonops; and (ii) that several specimens previously catalogued as S. hardyi in herpetological collections represented at least three independent lineages that are not closely related phylogenetically. Based on morphological and phylogenetic evidence, we place Luetkenotyphlus in the synonym of Siphonops. In addition, we described a new species, Siphonops maria sp. nov., from the state of Rio de Janeiro. It belongs to one of the unnamed lineages but is morphologically more distinct from S. hardyi than the other two. This new species is more closely related to the three currently recognized taxa of Luetkenotyphlus. Siphonops maria shares traditional morphological traits of this clade, which evolved a loss of teeth on the labial row of the maxillopalatine. Our findings challenge the understanding of Siphonopidae systematics and underscore the need for a detailed, comprehensive taxonomic revision of S. hardyi to clarify the distribution of morphologically similar lineages within the highly threatened Atlantic Forest.