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| Rhinatrema koki Wilkinson & Bittencourt-Silva, 2025 |
Abstract
We describe a new species of the rhinatrematid caecilian genus Rhinatrema Duméril & Bibron, 1841 from Guyana based on a single specimen previously confused with the type species of Rhinatrema, R. bivittatum (Guérin-Méneville, 1838), and the more recently described Guyanese endemic R. shiv Gower, Wilkinson, Sherratt & Kok, 2010. The new species is distinctive in external morphology (a substantial pale dorsal head spot, no substantial pale dorsal tail spot), cranial osteology (many more inner than outer mandibular teeth) and mitochondrial DNA sequence data. We propose revised morphological diagnoses for the constituent genera as part of a brief systematic overview of the Rhinatrematidae Nussbaum, 1977, provide a key to the species of Rhinatrema, and present improved images of the cranial osteology of R. shiv.
KEYWORDS: Caecilian, computed tomography, Herpetology, Neotropics, systematics, taxonomy
Systematics
Rhinatrematidae Nussbaum, 1977
Type genus: Rhinatrema Duméril & Bibron, 1841.
Diagnosis: The only caecilians with the paired m. adductores mandibulae externi extending through the upper temporal fenestra to the mid-dorsum of the cranium.
Phylogenetic definition: All caecilians more closely related to R. bivittatum than to Caecilia tentaculata.
Distribution: Northern South America.
Content: three genera, 15 species. Amazops Wilkinson, Reynolds & Jacobs, 2021; Epicrionops Boulenger, 1883a; Rhinatrema Duméril & Bibron, 1841
Rhinatrema Duméril & Bibron, 1841
Diagnosis: Rhinatrematid caecilians with fangs (enlarged maxillary and outer mandibular teeth) and the orbit entirely within the maxillopalatine.
Phylogenetic definition: All caecilians more closely related to R. bivittatum than to A. amazops or E. bicolor.
Distribution: Brazil, French Guiana, Guyana, Suriname, Venezuela.
Content: seven species (bivittatum, gilbertogili, koki sp. nov., nigrum, shiv, ron, uaiuai).
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| USNM 566004, holotype of Rhinatrema koki sp. nov. with head end (top), whole body (middle) and tail end (bottom). Scale bar gradations in mm. Photo by Harry Taylor (Natural History Museum, London). |
Rhinatrema koki sp. nov.,
Rhinatrema bivittatum Frost et al. (2006)
Rhinatrema shiv Cole et al. (2013)
Diagnosis: A Rhinatrema with a substantial pale dorsal head spot, no substantial pale dorsal tail spot and many more inner than outer mandibular teeth.
Etymology: The species is named in honour of Philippe J.R. Kok in recognition of his outstanding scholarship and scientific endeavours that have led to substantial and important contributions to the herpetology of the Guyana Shield. The specific epithet is a noun in the genitive case, but for nomenclatural purposes is considered a noun in apposition. Borrowing from the French, we suggest the vernacular ‘Kok’s Rhinatrème’.
Mark Wilkinson and Gabriela B. Bittencourt-Silva. 2025. Re-diagnoses of rhinatrematid genera and description of A New Species of Guyanese Rhinatrema Duméril & Bibron, 1841 (Amphibia: Gymnophiona: Rhinatrematidae). J. of Vertebrate Biology. 74(25060):25060.1-16. DOI: doi.org/10.25225/jvb.25060 [2 September 2025]
