DOI10.47051/YJTL1886

Published August 23, 2021. Updated September 1, 2026. Open access. Peer-reviewed.

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Big-lipped Lightbulb-Lizard (Riama labionis)

Reptiles of Ecuador | Sauria | Gymnophthalmidae | Riama labionis

English common name: Big-lipped Lightbulb-Lizard.

Spanish common name: Lagartija minadora labiosa.

Recognition: ♂♂ 14.9 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=6.0 cm. ♀♀ 15.6 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=5.9 cm..1,2 Lightbulb-lizards (Riama) are easily distinguished from other sympatric lizards by their fossorial habits and extremely reduced extremities, where the fore- and hind limbs are too short to meet when adpressed against the body.1,3 Riama labionis differs from co-occurring microteiids of the genus Andinosaura (Andinosaura crypta, A. oculata, and A. vieta)1 by possessing noticeably shorter limbs and lacking dorsolateral stripes (Fig. 1). From its co-occurring congeners R. colomaromani and R. konstanti, it is readily distinguished by its yellowish to orange-red ventral surface, where each scale features characteristic central brown smears or flecks.1,2 Adult males of R. labionis exhibit sexual dimorphism, differing from females by possessing a brighter red ventral coloration and a higher count of femoral pores.

Figure showing variation among individuals of Riama labionis

Figure 1: Individuals of Riama labionis from La Palma, Bolívar province, Ecuador. j=juvenile.

Natural history: Riama labionis is an exceptionally rare, cryptozoic lizard restricted to pristine old-growth and moderately disturbed high-evergreen montane forests and cloud forests.1,2 Notably, there are no known occurrences of this species in heavily transformed agricultural landscapes, such as pastures or plantations. This reptile exhibits semi-fossorial habits, living shallowly buried within loose, friable soils, decaying logs, and deep organic leaf-litter.2 Specimens have been recorded at depths of 20–50 cm beneath thick accumulations of leaf-litter in shaded interior forest microhabitats.2 Reproduction is oviparous; females deposit fixed clutches of two eggs in soft soil near tree bases, and communal nesting occurs, with multiple clutches occasionally recovered from a single nest site.2 When exposed, Big-lipped Lightbulb-Lizards attempt to rapidly retreat into the surrounding leaf-litter matrix; if captured, they may attempt to bite or readily employ caudal autotomy to shed the tail.2

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Conservation: Endangered Considered to be facing a high risk of extinction in the near future..4 Riama labionis is listed in this category due to its restricted range (~2,375 km2; Fig. 2), number of known localities (n=5; Appendix 1), and ongoing decline in the extent and quality of its remaining habitat driven by deforestation. Historical land-cover analyses indicate that over 55% of the species’ cloud forest habitat has been destroyed, largely converted through agricultural expansion, cattle ranching, and the replacement of native vegetation with exotic pine and eucalyptus plantations.5 Although models indicate that approximately 41% of its potential geographic range falls within the boundaries of the Reserva Ecológica Los Illinizas, the species has never been documented within this reserve. To date, confirmed records are restricted to a single privately protected area, the Otonga Reserve in Cotopaxi province.

Distribution: Riama labionis is endemic to an area of approximately 2,375 km2 in the Pacific slopes of the Andes in central Ecuador. Most records come from the Río Toachi drainage area in the border between Cotopaxi and Pichincha provinces, but a new record from La Palma, Bolívar province (see Appendix 1), extends its distribution 106 km to the south (Fig. 2).

Distribution of Riama labionis in Ecuador

Figure 3: Distribution of Riama labionis in Ecuador. See Appendix 1 for a complete list of the presence localities included in the map.

Etymology: The generic name Riama does not appear to be a reference to any feature of this group of lizards, but a matter of personal taste. John Edward Gray usually selected girls’ names to use on reptiles.6–9 The specific epithet labionis is the genitive singular case of the Latin noun labeo (=large lips),10 and refers to the large supralabial scale, which in this species is fused with the adjacent subocular.1

Where to observe: Riama labionis is has never been recorded during opportunistic visual encounter surveys due to its secretive habits and extremely restricted geographic distribution. Effective detection requires targeted sampling techniques, such as methodically raking deep leaf-litter matrices or overturning decaying logs in moist, shaded microhabitats. Along the lower-elevation trail systems of the Otonga Reserve, individuals have been successfully captured using drift-fence pitfall trap arrays.

Acknowledgments: Special thanks to Frank Pichardo and Amadeus Plewnia for their help and companionship during the field trip that resulted in the finding of the individuals of Riama labionis pictured here. This account was published with the support of Secretaría Nacional de Educación Superior Ciencia y Tecnología (programa INEDITA; project: Respuestas a la crisis de biodiversidad: la descripción de especies como herramienta de conservación; No 00110378), Programa de las Naciones Unidas (PNUD), and Universidad San Francisco de Quito (USFQ).

Author and photographer: Alejandro ArteagaaAffiliation: Fundación Khamai, Reserva Arlequín, Ecoruta Paseo del Quinde km 56, Santa Rosa de Mindo, Pichincha 171202, Ecuador.

Academic reviewer: Jeffrey D CamperbAffiliation: Department of Biology, Francis Marion University, Florence, USA.

How to cite? Arteaga A (2026) Big-lipped Lightbulb-Lizard (Riama labionis). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: www.reptilesofecuador.com. https://doi.org/10.47051/YJTL1886

Literature cited:

  1. Kizirian DA (1996) A review of Ecuadorian Proctoporus (Squamata: Gymnophthalmidae) with descriptions of nine new species. Herpetological Monographs 10: 85–155. https://doi.org/10.2307/1466981
  2. Field notes, Reptiles of Ecuador book project.
  3. Doan TM, Castoe TA (2005) Phylogenetic taxonomy of the Cercosaurini (Squamata: Gymnophthalmidae), with new genera for species of Neusticurus and Proctoporus. Zoological Journal of the Linnean Society 143: 405–416.
  4. Cisneros-Heredia DF, Yánez-Muñoz M (2017) Riama labionis. The IUCN Red List of threatened species. Available from: www.iucnredlist.org. https://doi.org/10.2305/IUCN.UK.2017-2.RLTS.T50950517A50950524.en
  5. MAE (2012) Línea base de deforestación del Ecuador continental. Ministerio del Ambiente del Ecuador, Quito, 30 pp.
  6. Gray JE (1831) Description of a new genus of ophisaurean animal, discovered by the late James Hunter in New Holland. Treuttel, Würtz & Co., London, 40 pp.
  7. Gray JE (1831) A synopsis of the species of the class Reptilia. In: Griffith E, Pidgeon E (Eds) The animal kingdom arranged in conformity with its organization. Whittaker, Treacher, & Co., London, 1–110.
  8. Gray JE (1838) Catalogue of the slender-tongued saurians, with descriptions of many new genera and species. Annals and Magazine of Natural History 1: 274–283.
  9. Gray JE (1845) Catalogue of the specimens of lizards in the collection of the British Museum. Trustees of the British Museum, London, 289 pp.
  10. Brown RW (1956) Composition of scientific words. Smithsonian Books, Washington D.C., 882 pp.

Appendix 1: Locality data used to create the distribution map of Riama labionis in Ecuador (Fig. 2). Asterisk (*) indicates type locality.

CountryProvinceLocalitySource
EcuadorBolívarLa Palma, 700 m SW ofArteaga et al. 2026
EcuadorCotopaxiBosque Integral OtongaTorres-Carvajal & Salazar-Valenzuela 2012
EcuadorCotopaxiPalo QuemadoKizirian 1996
EcuadorCotopaxiSan Francisco de Las Pampas*Kizirian 1996
EcuadorPichinchaTandapiKizirian 1996