Amazops amazops Wilkinson, Reynolds & Jacobs, 2021
|Species Description: Wilkinson M, Reynolds RP, Jacobs JF. 2021. A new genus and species of rhinatrematid caecilian (Amphibia: Gymnophiona: Rhinatrematidae) from Ecuador. Herpetological Journal 31:27-34.|
Amazops amazops is a caecilian member of the Rhinatrematidae family described by one female specimen collected 30 years prior to its description with a total length of 173 mm. From the dorsal view, the head is more V-shaped than U-shaped, wider than it is deep, and compressed dorsoventrally. From a ventral view, the mouth is subterminal and the lower jaws are roughly as wide as the head. The tip of the lower jaws is more rounded than the tip of the snout. The distance from this tip to the corner of the mouth is 7.0 mm, which is slightly smaller than the distance from the snout tip to the first nuchal groove behind the corner of the mouth. Laterally, the head tapers gently to the front of the eyes, but sharply from the level of the nostrils. The lips of the mouth run straight, but turn down at the corner of the mouth. Furthermore, the lower jaws are robust and nearly as deep as the upper jaws. From the back of the head, it narrows slightly to roughly a third of the distance between the nares and eyes (3.0 mm). The nares meanwhile are smaller than the eyes, subcircular in shape on the left but tear-shaped and closer to the snout tip on the right. Distance between the nares is 1.5 mm, which is half the distance between the naris to the eye. The eyes of A. amazops are circular and small (diameter 0.4 mm). They are slightly raised from nearby skin and equal distance from the top of the head to the lips from a side view. Amazops amazops have small tentacular apertures of 0.6 mm, in nearly horizontal arched slits that curve ventrally at their ends. The apertures extend from the middle of the front edge of the eyes, and the tentacular ducts that run from the tentacles to the vomeronasal organ are visible through the adjacent skin (Wilkinson et. al 2021).
The teeth point at angles 30 - 45 posteriorly and are both lightly recurved and bicuspid. There are roughly 36 outer mandibular teeth, larger than the 42 premaxillary-maxillary teeth, and 40 vomeropalatine teeth, larger than the 24 inner mandibular teeth. Sub-cylindrical in shape, the body of A. amazops is mostly compressed dorsoventrally, less so posteriorly, and not compressed at vent level. The body narrows more posteriorly than anteriorly (Wilkinson et. al 2021). The first collar region and first nuchal groove is poorly visible dorsolaterally and invisible ventrally. The second nuchal groove, which is larger than the first, is barely visible dorsally, but clearly visible laterally and ventrally. Meanwhile, the third nuchal groove is complete and bows slightly anteromedially, similarly to subsequent annular grooves. The second collar region contains four regularly spaced, extending dorsal grooves that bow barely anteromedially and slightly increase in length dorsolaterally. Beyond the collars, there are 247 ventrally complete, annular grooves that mostly curve posteromedially on the venter, except for the last complete groove before the vent. This final groove curves anteromedially. In addition, two grooves are incomplete due to interruption by the vent and disc (Wilkinson et. al 2021).
Transverse rings of scales can be found throughout the body of A. amazops, except for those interrupted by the vent. One row of small and partially circular scales can be observed below the dorsal grooves and in shallow pockets on the second nuchal collar. Meanwhile, two distinct rows (posteriorly larger and anteriorly smaller) of scales can be observed in pockets on the posteriorly mid-body. Scattered scales may be seen posterior to the larger row of scales. Singular row scales overlap with adjacent rules. Mid-ventral scales are superficial to their adjacent scales, which are superficial to their adjacent scales and so on. These successive scales offset by shifting half a scale transversely (Wilkinson et. al 2021).
The slightly longitudinal vent of A. amazops is bordered by irregular and subdivided denticulations, with the posterior denticulations being pigmented and glandular and the anterior denticulations being pale with short grooves. These denticulations form an egg-shaped disc around the vent. Denticulations can be found on the the narrow anterior region of the disc. There are no papillae by the vent, in addition to no melanophores in the viscera (Wilkinson et. al 2021).
Amazops amazops has a tail with ten complete and an eleventh incomplete dorsoventrally annular grooves. This tail is moderately long at 7.6 mm in length, 3.0 mm in width, and 3.5 mm in depth. The ventral surface is skinny and the tail is slightly compressed laterally, tapering in a dorsal view and blunting at the tip in a lateral view. The dorsal and ventral margins are also symmetrical from a lateral view (Wilkinson et. al 2021).
Amazops amazops has several morphological, osteological, and coloration characteristics that distinguish it from other rhinatrematids. Firstly, they have more elongated squamosals that contribute to their margin of orbit and occupy the anterior areas, whereas other rhinatrematids have maxillopalatine occupying these anterior areas. The unique squamosals result in lack of contact between their quadrate and maxillopalatine, as well as contact to the anterior frontals of their upper temporal fenestrae. In addition, A. amazops has large, undivided pterygoids, representative of an ancestral caecilian condition, and unlike other rhinatrematids. There are no indications of pterygoid process in the A. amazops’ quadrates. Most notably, A. amazops has less than four annular grooves, which are interrupted by its vent. In combination with their low number of annular grooves (< 275) and uniform color, they can readily be distinguished from other Rhinatrematidae, except for E. colombianus, which is the only known species with more than 225 annular grooves (Wilkinson et. al 2021).
Presumably in preservative, A. amazops is a brownish lavender shade, paler on its head and throat. Faint, narrow, and pale paramandibular stripes start from the lips to the head’s ventral surface. A distinctively pale second nuchal groove can be seen on the collar region from a ventral view. The snout tip around the nares is paler in shade than the areas around the eyes, which have a gray lens and darker periphery. The area around the vent is pale, especially anteriorly; the vent denticulations are unpigmented. The nearby annular grooves have light posterior margins and darker anterior areas away from the glands (Wilkinson et. al 2021).
Only one holotype has been found at the time of the species description, so no variation has been recorded (Wilkinson et. al 2021)
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Ecuador
At the locality Finca Virgen Da Dolores, within Ecuador’s Province of Orellana, A. amazops can be found under the rocks of the Hollin-Loreto road. The road itself has seeping waters and soft, red, and muddy ground. This region is 1000 m above sea level (Wilkinson et. al 2021).
Life History, Abundance, Activity, and Special Behaviors
Like other rhinatrematids, A. amazops is oviparous and dependent on bodies of water for reproduction, especially due to their aquatic larval stages (Wilkinson et. al 2021).
Other species of rhinatrematids produce ovarian eggs of 0.8 mm in diameter and remain with the eggs until the larvae hatch. These mothers also utilize maternal dermatophagy, where their larvae eat their specially modified skin (Mauro et. al 2014)
At the time of the species description, little information is known about A. amazops larvae. However, in other rhinatrematids, the larvae have small, external gills of varying sizes and arrangement and lateral lines. They have aquatic life stages, and the larval stage itself usually exceeds the annual breeding season. The larvae feed on the specially modified skin of the mothers and usually hide amongst debris or plants (San Mauro et. al 2014; Muller 2019).
Solely based on morphology, A. amazops was identified to be a part of the family Rhinatrematidae. However, ancestral features such as elongated squamosals and undivided pterygoid bones indicate a basal placement to all other rhinatrematids (Wilkinson and Nussbaum 2006; Wilkinson et. al 2021). Wilkinson et. al (2021) did not use fossils for comparison to determine phylogenetic relationships because the families within the Gymnophiona order all have extremely different morphologies due to different environments.
The name Amazops amazops is combines the origin of the holotype’s discovery and its unique skeletal characteristics. The species was found in the Amazon and its squamosal bone is extended, contributing to the margin of its eye and its pterygoid bone is undivided (Wilkinson et. al 2021).
Wilkinson et. al (2021) provides CT scans of the skull and tail of Amazops amazops, as well as descriptions of these scans.
Müller, H. (2019). "Development and demography of larval Epicrionops bicolor (Amphibia: Gymnophiona: Rhinatrematidae)." Neotropical Biodiversity, 6. [link]
San Mauro, D., Gower, D.J., Müller, H., Loader, S.P., Zardoya, R., Nussbaum, R.A., Wilkinson, M (2014). "Life-history evolution and mitogenomic phylogeny of caecilian amphibians." Molecular Phylogenetics and Evolution , 73, 177-189. [link]
Wilkinson, M., Nussbaum R.A. (2006). "Caecilian Phylogeny and Classification." Reproductive Biology and Phylogeny Series, 5, 39-78.
Wilkinson, M., Reynolds, R.P., Jacobs, J.F. (2021). "A new genus and species of rhinatrematd caecilian (Amphibia: Gymnophiona: Rhinatrematdae) from Ecuador." Herpetological Journal, 31, 27-34. [link]
Originally submitted by: Hong Nguyen (2022-10-12)
Description by: Hong Nguyen (updated 2022-10-12)
Distribution by: Hong Nguyen (updated 2022-10-12)
Life history by: Hong Nguyen (updated 2022-10-12)
Larva by: Hong Nguyen (updated 2022-10-12)
Comments by: Hong Nguyen (updated 2022-10-12)
Edited by: Ann T. Chang (2022-10-12)
Species Account Citation: AmphibiaWeb 2022 Amazops amazops <https://amphibiaweb.org/species/9310> University of California, Berkeley, CA, USA. Accessed May 31, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 31 May 2023.
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