[Herpetology • 2025] Rhinatrema koki • Re-diagnoses of rhinatrematid genera and description of A New Species of Guyanese Rhinatrema Duméril & Bibron, 1841 (Gymnophiona: Rhinatrematidae)

 

 Rhinatrema koki

Wilkinson & Bittencourt-Silva, 2025 

DOI: doi.org/10.25225/jvb.25060

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).

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]

 

[Herpetology • 2021] Amazops amazops • A New Genus and Species of Rhinatrematid Caecilian (Gymnophiona: Rhinatrematidae) from Ecuador

Amazops amazops 

Wilkinson, Reynolds & Jacobs, 2021

DOI: 10.33256/hj31.1.2734

 twitter.com/HerpJournal 

Abstract

 A new genus and species of rhinatrematid caecilian, Amazops amazops gen. et sp. nov., is described based on a single specimen from Orellana, Ecuador collected in 1990. Among other features the new taxon differs from all other rhinatrematid caecilians in having less than four annular grooves interrupted in the region of the vent and in the squamosal contributing to the bony margin of the orbit. A consideration of its distinctive morphology suggests that it is plausible that the new taxon is the sister taxon of all other rhinatrematid caecilians. That the genus is known from a single specimen, and that this is the first new rhinatrematid species from the Andes described for more than 50 years, highlights the poor sampling (collecting) of rhinatrematid caecilians and limited knowledge of their diversity.

Keywords: Andes, biodiversity, computed tomography, morphology, South America, systematics, taxonomy

USNM 320729, holotype of Amazops amazops 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).

CT scan of skull USNM 320729, holotype of Amazops amazops sp. nov.

The holotype of Amazops amazops sp. nov. in life [USNM 320729]. 

Photo by William W. Lamar.

Amazops gen. nov. 

Diagnosis. Rhinatrematid caecilians with the squamosal contributing to the margin of the orbit. 

Content: A single species Amazops amazops, sp. nov., the type by monotypy and by designation. 

Etymology: The name is a portmanteau word combining reference to the Amazonian provenance of the type and only known species and the distinctive topological relationships of its eye and orbit, particularly the contribution of the squamosal to the bony margin of the orbit, which is unknown in any other rhinatrematid. As mandated by the code, gender is masculine. 

Remarks: Three other features of the only known specimen of this genus are distinctive, known in no other rhinatrematids and might be diagnostic for the genus: lack of contact between the quadrate and maxillopalatine, contact between the squamosal and frontal and the small number of annular grooves that are interrupted by the vent. 

  

Amazops amazops sp. nov.

 

Etymology. As for the genus. For nomenclatural purposes the specific epithet is considered to be a genderless noun in apposition.

Remarks. That the species is known from a single specimen is sufficient reason to suggest that the IUCN conservation status of the species should be data deficient. Effort is needed to identify populations of this distinctive lineage as a precursor to any meaningful study of its natural history. Based on it being a rhinatrematid it is assumed that it will share the reproductive mode of the other rhinatrematids, as far as is known, in being oviparous with an aquatic larval stage (San Mauro et al., 2014, Müller, 2020) and thus being dependent on water bodies for its reproduction. 

 Map showing type locality (black star) of Amazops amazops sp. nov.

 Mark Wilkinson, Robert P. Reynolds and Jeremy F. Jacobs. 2021. A New Genus and Species of Rhinatrematid Caecilian (Amphibia: Gymnophiona: Rhinatrematidae) from Ecuador. Herpetological Journal. (31); 27-34. DOI: 10.33256/hj31.1.2734

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