DOI10.47051/MNSV6360

Published October 18, 2020. Updated September 2, 2026. Open access. Peer-reviewed.

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Orcés’ Lightbulb-Lizard (Riama orcesi)

Reptiles of Ecuador | Sauria | Gymnophthalmidae | Riama orcesi

English common names: Orcés’ Lightbulb-Lizard.

Spanish common names: Lagartija minadora de Orcés.

Recognition: ♂♂ 15.7 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=5.9 cm. ♀♀ 13.6 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.1,2 Riama orcesi is one of three species of its genus known to occur in Napo province. Riama orcesi differs from the other two species (R. anatoloros and R. raneyi) by having light orangish dorsolateral stripes on the anterior portion of the tail (Fig. 1). Individuals of R. orcesi further differ from those of R. raneyi by being smaller, more colorful, and having a complete series of superciliary scales.2 Adult males of R. orcesi differ from females by having broader heads, darker colored venters,3 and, usually, a bright reddish tail.

Variation among individuals of Riama orcesi

Figure 1: Individuals of Riama orcesi from Napo province, Ecuador: Río Quijos (); Virgen de Guacamayos ().

Natural history: Riama orcesi is a rarely observed, secretive fossorial lizard inhabiting pristine to heavily modified cloud forests and high evergreen montane forests. It also persists in human-modified mosaic landscapes that blend active crop fields, cattle pastures, rural homesteads, and fragmented remnants of native woodland.4 These reptiles spend the majority of their life within self-excavated subterranean galleries in friable soils or sheltered beneath large rocks, decaying logs, and leaf debris.4 Reproduction is oviparous; females deposit fixed clutches of two eggs beneath large rocks.3 When unearthed or exposed, individuals attempt to rapidly retreat underground; if captured, they may bite or employ caudal autotomy to shed the tail. Like its congeners, Orcés’ Lightbulb-Lizards exhibit extreme stenothermy, rendering them vulnerable to thermal stress—rapidly succumbing to elevated temperatures if exposed to direct sunlight or handled continuously for more than a few seconds. Avian predation has been documented, with an antpitta (Grallariidae) recorded preying upon an individual.5 In the Papallacta River valley, R. orcesi occurs sympatrically with R. raneyi; microhabitat partitioning and stable coexistence between these sympatric congeners are likely facilitated by morphological divergence, as R. raneyi possesses a larger body size paired with proportionally shorter limbs.2

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Conservation: Least Concern Believed to be safe from extinction given current circumstances.. Riama orcesi is recommended for downlisting to this category, shifting from its current Vulnerable status,6,7 because the species occurs in four major protected areas (Antisana Ecological Reserve, Cayambe Coca National Park, Colonso Chalupas Biological Reserve, and Sumaco National Park) and is distributed over an area that retains the majority (~93.4%) of its original forest cover.8 Therefore, the species is considered to be facing no major immediate extinction threats.

Distribution: Riama orcesi is endemic to an area of approximately 2,497 km2 in the Amazonian slopes of the Andes of northern Ecuador (Fig. 2).

Distribution of Riama orcesi in Ecuador

Figure 2: Distribution of Riama orcesi in Ecuador. The star corresponds to the type locality: Cuyuja, 3.3 km ESE of*, Napo province. 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.9–12 The specific epithet orcesi honors Dr. Gustavo Orcés (1903–1999), in recognition of his many contributions to the herpetology of Ecuador.3

Where to observe: Riama orcesi is rarely recorded during general visual encounter surveys unless field researchers actively target its subterranean microhabitats by methodically excavating loose, friable soils or overturning large rocks and decaying logs at or near suitable montane forest patches. Near the town of Cuyuja in Napo province, dedicated microhabitat searches lasting at least four hours consistently yield an encounter rate of approximately 3–7 individuals.

Acknowledgments: Special thanks to Amanda Quezada, Harry Turner, and Jorge Castillo for their help and companionship during the search of specimens of Riama orcesi in the field. Thanks to Frank Pichardo for providing natural history data of R. orcesi. Thanks to Amanda Quezada for the post-processing of images.

Authors: Alejandro ArteagaaAffiliation: Fundación Khamai, Reserva Arlequín, Ecoruta Paseo del Quinde km 56, Santa Rosa de Mindo, Pichincha 171202, Ecuador. and Miguel Ángel Méndez-GaleanobAffiliation: Grupo de Biodiversidad y Sistemática Molecular, Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Bogotá, Colombia.

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

Photographer: Jose VieiradAffiliation: Tropical Herping (TH), Quito, Ecuador.,eAffiliation: ExSitu, Quito, Ecuador.

How to cite? Arteaga A, Méndez-Galeano MA (2026) Orcés’ Lightbulb-Lizard (Riama orcesi). 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/MNSV6360

Literature cited:

  1. Pazmiño-Otamendi G (2022) Riama orcesi. In: Torres-Carvajal O, Pazmiño-Otamendi G, Ayala-Varela F, Salazar-Valenzuela D (Eds) Reptiles del Ecuador. Museo de Zoología, Pontificia Universidad Católica del Ecuador. Available from: https://bioweb.bio
  2. 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
  3. Kizirian DA (1995) A new species of Proctoporus (Squamata: Gymnophthalmidae) from the Andean Cordillera Oriental of northeastern Ecuador. Journal of Herpetology 29: 66–72. https://doi.org/10.2307/1565087
  4. Field notes, Reptiles of Ecuador book project.
  5. Photographic record by Frank Pichardo.
  6. Cisneros-Heredia DF, Valencia J, Brito J, Almendáriz A, Muñoz G (2019) Riama orcesi. The IUCN Red List of threatened species. Available from: www.iucnredlist.org. https://doi.org/10.2305/IUCN.UK.2019-3.RLTS.T50950530A50950537.en
  7. IUCN (2001) IUCN Red List categories and criteria: Version 3.1. IUCN Species Survival Commission, Gland and Cambridge, 30 pp.
  8. MAE (2012) Línea base de deforestación del Ecuador continental. Ministerio del Ambiente del Ecuador, Quito, 30 pp.
  9. 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.
  10. 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.
  11. 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.
  12. Gray JE (1845) Catalogue of the specimens of lizards in the collection of the British Museum. Trustees of the British Museum, London, 289 pp.

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

CountryProvinceLocalitySource
EcuadorNapoAbove El ChacoKizirian 1996
EcuadorNapoBetween Papallacta and BaezaReptiles of Ecuador book database
EcuadorNapoColonso ChalupasElicio Tapia, pers. comm.
EcuadorNapoCosanga, 1 km N ofReptiles of Ecuador book database
EcuadorNapoCuyujaReptiles of Ecuador book database
EcuadorNapoCuyuja, 3.3 km ESE of*Kizirian 1996
EcuadorNapoCuyuja, 7 km E ofKizirian 1996
EcuadorNapoCuyuja, 9 km E ofKizirian 1996
EcuadorNapoEstación repetidoraJose Simbaña, pers. comm.
EcuadorNapoGuango LodgeReptiles of Ecuador book database
EcuadorNapoSendero GuacamayosThis work; Fig. 1
EcuadorNapoSumaco camp 2Reptiles of Ecuador book database
EcuadorNapoTena–Quito 1Kizirian 1996
EcuadorNapoTena–Quito 2Kizirian 1996
EcuadorNapoVertiente E Volcán SumacoPazmiño-Otamendi 2020