Published October 11, 2020. Updated September 9, 2026. Open access. Peer-reviewed. | Purchase book ❯ |
Unicolored Lightbulb-Lizard (Riama unicolor)
Reptiles of Ecuador | Sauria | Gymnophthalmidae | Riama unicolor
English common names: Unicolored Lightbulb-Lizard, Drab Lightbulb-Lizard.
Spanish common names: Lagartija minadora de vientre rojo.
Recognition: ♂♂ 14.5 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=6.8 cm. ♀♀ 14.5 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=6.5 cm..1 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 Riama unicolor differs from congeners with which it may overlap geographically (R. colomaromani, R. tarletonorum, R. simotera, and R. raneyi) by having a reddish tail underside bearing black longitudinal lines, whereas the other species feature predominantly black subcaudal surfaces.1,2 From the morphologically similar but allopatric R. higginsi and R. konstanti, it differs in attaining a larger overall body size and in displaying clearly defined black longitudinal stripes on the underside of the tail.2 Riama unicolor exhibits sexual dimorphism, with males differing from females by possessing broader heads and a more vibrantly patterned lower flank coloration (Fig. 1).
Figure 1: Individuals of Riama unicolor from Ecuador: La Libertad, Carchi province (); Tabacundo, Pichincha province (). j=juvenile.
Natural history: Riama unicolor is a locally abundant, cryptozoic fossorial lizard inhabiting old-growth to heavily disturbed montane cloud forests and humid highland shrublands. This species persists within human-modified mosaic landscapes—occupying agricultural fields, pastures, fragmented woodland remnants, and suburban residential gardens within major high-Andean urban centers.2,3 These lizards spend the majority of their life cycle within subterranean tunnels excavated in loose, friable soils, or concealed beneath large boulders, decaying logs, organic leaf debris, and artificial cover objects such as flowerpots.1,3 Diurnal activity is primarily subterranean, though individuals are occasionally observed crossing open asphalt roads during full daylight.3 In captive settings, R. unicolor feeds opportunistically on small soft-bodied invertebrates and dipteran larvae.1 When disturbed or unearthed, Unicolored Lightbulb-Lizards seek immediate refuge within crevices or bury themselves; if handled, they may attempt to bite or readily employ caudal autotomy. Like other Riama, R. unicolor exhibits pronounced stenothermy and extreme physiological thermal sensitivity—rapidly succumbing to critical thermal maxima if exposed to direct insolation or handled continuously for even brief intervals.1 Anuran predation has been documented, with an individual of the Riobamba Marsupial Frog (Gastrotheca riobambae) recorded regurgitating a R. unicolor.1
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Conservation: Vulnerable Considered to be facing a high risk of extinction in the mid-term future..4 Riama unicolor is listed in this category due to its limited extent of occurrence (~6,682 km2), severe population fragmentation, and widespread, documented population declines.4 Land-cover assessments reveal that approximately 64.3% of its original montane habitat has been destroyed or converted,5 driven predominantly by urban expansion, intensive agriculture, livestock grazing, and the establishment of exotic pine and eucalyptus silviculture.3,4 Remarkably, R. unicolor exhibits a degree of synanthropy, persisting within suburban green spaces and private gardens despite extensive environmental transformation,3 rendering it one of the few native reptile species capable of surviving within the urban limits of Quito.3
Distribution: Riama unicolor is native to an area of approximately 6,682 km2 in the inter-Andean valleys of northern Ecuador (Fig. 2) and southern Colombia.
Figure 2: Distribution of Riama unicolor 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 unicolor is a Latin adjective that probably refers to the nearly unicolored dorsal pattern.1
Where to observe: Unicolored Lightbulb-Lizards are recorded rarely unless actively searched for by digging in areas of soft soil or by turning over rocks and logs in suitable habitats. Prime locations for encountering the species include Refugio Pasochoa and Reserve Pulhulahua.
Special thanks to Walter Jennings for symbolically adopting the Unicolored Lightbulb-Lizard and helping bring the Reptiles of Ecuador book project to life.
Acknowledgments: Special thanks to Amanda Quezada, Frank Pichardo, Harry Turner, and Jorge Castillo for their help and companionship during the search of specimens of Riama unicolor in the field. Thanks to Diego Piñán and María Jose Quiroz for providing locality data of R. unicolor. Thanks to Andres Pérez for the post-processing of images. 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: 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.
Photographers: Jose VieiracAffiliation: Tropical Herping (TH), Quito, Ecuador.,dAffiliation: ExSitu, Quito, Ecuador. and Alejandro ArteagaaAffiliation: Fundación Khamai, Reserva Arlequín, Ecoruta Paseo del Quinde km 56, Santa Rosa de Mindo, Pichincha 171202, Ecuador.
How to cite? Arteaga A (2026) Unicolored Lightbulb-Lizard (Riama unicolor). 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/PEFN1380
Literature cited:
- 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
- Arteaga A, Tovar-Ortiz A, Vieira J, Bringsøe H, Quezada A, Camper J, Harris K (2026) Six new species of lizards (Riama, Sauria, Gymnophthalmidae) from the high Andes of Ecuador. In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador. Second Edition. Khamai Foundation & Tropical Herping, Quito, 1082–1119. https://doi.org/10.47051/GZNM5526
- Field notes, Reptiles of Ecuador book project.
- Cisneros-Heredia DF, Brito J, Yánez-Muñoz M, Almendáriz A (2019) Riama unicolor. The IUCN Red List of threatened species. Available from: www.iucnredlist.org. https://doi.org/10.2305/IUCN.UK.2019-3.RLTS.T50950566A50950573.en
- MAE (2012) Línea base de deforestación del Ecuador continental. Ministerio del Ambiente del Ecuador, Quito, 30 pp.
- 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.
- 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.
- 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.
- 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 unicolor in Ecuador (Fig. 2).
| Country | Province | Locality | Source |
| Colombia | Nariño | Guachuncal | iNaturalist; photo examined |
| Colombia | Nariño | La Riqueza | iNaturalist; photo examined |
| Ecuador | Carchi | El Manzanar | Reptiles of Ecuador book database |
| Ecuador | Carchi | Gruta de la Paz | Galarza-Verkovitch 2020 |
| Ecuador | Carchi | Huaca | Aguirre et al. 2014 |
| Ecuador | Carchi | La Libertad | Arteaga et al. 2026 |
| Ecuador | Carchi | Montúfar | Kizirian 1996 |
| Ecuador | Carchi | San Gabriel | Reptiles of Ecuador book database |
| Ecuador | Carchi | Tulcán | Reptiles of Ecuador book database |
| Ecuador | Carchi | Tulcán, 14 km W of | Photo by Luis Coloma |
| Ecuador | Carchi | Vía Montúfar–Atal | Sánchez-Pacheco et al. 2012 |
| Ecuador | Carchi | Vía San Gabriel–El Angel | Reptiles of Ecuador book database |
| Ecuador | Imbabura | Chachimbiro | Kizirian 1996 |
| Ecuador | Imbabura | Cuicocha | Kizirian 1996 |
| Ecuador | Imbabura | Cuicocha, 2.6 km W of | Aguirre et al. 2014 |
| Ecuador | Imbabura | Cuicocha, 4.8 km W of | Aguirre et al. 2014 |
| Ecuador | Imbabura | Hacienda Zuleta | Photo by Anton Sorokin |
| Ecuador | Imbabura | Islote Yerovi | Almendáriz & Orcés 2004 |
| Ecuador | Imbabura | Otavalo, 8 km NW of | Kizirian 1996 |
| Ecuador | Imbabura | Perihuela | Reptiles of Ecuador book database |
| Ecuador | Imbabura | Pimampiro | Kizirian 1996 |
| Ecuador | Imbabura | Quiroga, 7 km W of | Kizirian 1996 |
| Ecuador | Imbabura | San Pablo | Kizirian 1996 |
| Ecuador | Imbabura | San Rafael, 3 km SE of | Doan 2003 |
| Ecuador | Imbabura | Sigsipamba | iNaturalist; photo examined |
| Ecuador | Imbabura | Tumbabiro | Aguirre et al. 2014 |
| Ecuador | Imbabura | Urcusiquí | Kizirian 1996 |
| Ecuador | Imbabura | Vía Cahuasquí–Urcuquí | Photo by Diego Piñán |
| Ecuador | Imbabura | Vía Cotacachi–Quiroga | iNaturalist; photo examined |
| Ecuador | Imbabura | Vía Ibarra-Mariano Acosta | Arteaga et al. 2026 |
| Ecuador | Imbabura | Vía Tabacundo–Mojanda | KU 221766; VertNet |
| Ecuador | Imbabura | Yaguachi | Galarza-Verkovitch 2020 |
| Ecuador | Pichincha | Aloguincho | Galarza-Verkovitch 2020 |
| Ecuador | Pichincha | Between Quito and Papallacta | Kizirian 1996 |
| Ecuador | Pichincha | Bosque de Pasochoa | Field notes of Felipe Campos |
| Ecuador | Pichincha | Calacalí | Reptiles of Ecuador book database |
| Ecuador | Pichincha | Cayambe | Kizirian 1996 |
| Ecuador | Pichincha | Cayambe, 10 km N of | Kizirian 1996 |
| Ecuador | Pichincha | Chillogallo | Kizirian 1996 |
| Ecuador | Pichincha | Guagua Pichincha, slopes | Kizirian 1996 |
| Ecuador | Pichincha | Hacienda Gorzon | Kizirian 1996 |
| Ecuador | Pichincha | Hacienda Olalla | Kizirian 1996 |
| Ecuador | Pichincha | Hacienda Pesillo | Almendáriz & Orcés 2004 |
| Ecuador | Pichincha | La Josefina | iNaturalist; photo examined |
| Ecuador | Pichincha | La Playita | iNaturalist; photo examined |
| Ecuador | Pichincha | La Unión | iNaturalist; photo examined |
| Ecuador | Pichincha | Machachi | Sánchez-Pacheco et al. 2012 |
| Ecuador | Pichincha | Mirador de Guápulo | iNaturalist; photo examined |
| Ecuador | Pichincha | Mirador del Pulhulahua | iNaturalist; photo examined |
| Ecuador | Pichincha | Nono | María Jose Quiroz, pers. comm. |
| Ecuador | Pichincha | Paloguillo | Field notes of Juan Freile |
| Ecuador | Pichincha | Pan-American highway at Equator | USNM 196250; VertNet |
| Ecuador | Pichincha | Pasochoa | Kizirian 1996 |
| Ecuador | Pichincha | Pifo, 12 km E of | Kizirian 1996 |
| Ecuador | Pichincha | Quito | Kizirian 1996 |
| Ecuador | Pichincha | Quito, 40 SE of | Sánchez-Pacheco et al. 2012 |
| Ecuador | Pichincha | Quito, calles Brazil y Zamora | Photo by Viviana Jaramillo |
| Ecuador | Pichincha | Quito, Colegio Fernandez Madrid | iNaturalist; photo examined |
| Ecuador | Pichincha | Quito, El Inca | iNaturalist; photo examined |
| Ecuador | Pichincha | Quito, Parque Metropolitano | iNaturalist; photo examined |
| Ecuador | Pichincha | Quito, Parque Rumipamba | Photo by Finding Species |
| Ecuador | Pichincha | Quito, PUCE | Reptiles of Ecuador book database |
| Ecuador | Pichincha | Río Machángara | Kizirian 1996 |
| Ecuador | Pichincha | San Jorge Ecolodge | Photo by Clint King |
| Ecuador | Pichincha | Tabacundo | Kizirian 1996 |
| Ecuador | Pichincha | Tabacundo, 2.5 km W of | Kizirian 1996 |
| Ecuador | Pichincha | Tabacundo, 3.8 km W of | Reptiles of Ecuador book database |
| Ecuador | Pichincha | Tabacundo, 5.9 km W of | Kizirian 1996 |
| Ecuador | Pichincha | Tabacundo, 7 km N of | This work; Fig. 1 |
| Ecuador | Pichincha | Valle de los Chillos | Kizirian 1996 |
| Ecuador | Pichincha | Vía a Molinuco | Galarza-Verkovitch 2020 |