Sabin’s Lightbulb-Lizard (Riama ellasabinae)

Reptiles of Ecuador | Sauria | Gymnophthalmidae | Riama ellasabinae

English common name: Sabin’s Lightbulb-Lizard.

Spanish common name: Lagartija minadora de Sabin.

Recognition: ♂♂ 14 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=4.2 cm. ♀♀ 13 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=5.6 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.^2,3 The Sabin’s Lightbulb-Lizard (R. ellasabinae) may overlap geographically with R. balneator, from which it differs by having a loreal scale, and R. stigmatoral, from which it differs by having reddish (as opposed to black) ventral surfaces. Riama ellasabinae resembles R. anatoloros in size, coloration, and lepidosis, but it differs from this allopatric species by having a loreal scale and lacking distinct dorsolateral stripes.¹ Adult males of R. ellasabinae exhibit sexual dimorphism, differing from females by their larger overall size, broader heads, and typically a vibrant red coloration on the lower flanks (Fig. 1) and ventral surfaces.

Figure showing variation among individuals of Riama ellasabinae

Figure 1: Individuals of Riama ellasabinae from Sendero Sardinayacu, Morona Santiago province, Ecuador.

Natural history: Riama ellasabinae is a rarely encountered, semi-fossorial lizard that primarily inhabits pristine to moderately disturbed cloud forests and lower evergreen montane forests.¹ It also persists within mosaic landscapes composed of pastures, rural homesteads, and fragmented remnants of native vegetation. These lizards spend the vast majority of their lives within self-excavated tunnel networks in friable soils or concealed beneath rocks, decomposing logs, and deep leaf-litter matrices,¹ though diurnal surface activity is occasionally observed.⁴ Reproduction is presumed to be oviparous, but clutch sizes have not yet been reported. When unearthed or otherwise exposed, individuals rapidly retreat underground; if captured, they may attempt to bite or will readily employ caudal autotomy to shed the tail. Lightbulb lizards in general exhibit extreme stenothermy and are highly susceptible to thermal stress, rapidly succumbing to elevated temperatures if exposed to direct sunlight or even if handled continuously for more than a few seconds.

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Conservation: Least Concern Believed to be safe from extinction given current circumstances..¹ Riama ellasabinae is recommended for listing to this category because the species is distributed over a comparatively wide region (greater than 10,000 km²) of the Amazonian slopes of the Andes that holds large areas of continuous unspoiled forest. It is estimated,¹ that approximately 81% of the species’ forest habitat is still standing.

Distribution: Riama ellasabinae is endemic to an area of approximately 13,131 km² along the Amazonian slopes of the Andes in central and southern Ecuador (Fig. 2).

Figure 2: Distribution of Riama ellasabinae in Ecuador. The star corresponds to the type locality: Sendero Sardinayacu, Morona Santiago 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.^8–11 The species is named after Ella Sabin, granddaughter of American philanthropist Andrew Sabin. The Sabin family supports conservation and field research of reptiles and has protected over 264,365 acres of critical habitat throughout the world.¹

Where to observe: Riama ellasabinae is rarely encountered unless researchers actively target its microhabitat by methodically raking deep leaf-litter matrices or overturning decaying logs within well-preserved forest tracts. However, in specific optimal localities, population densities can be surprisingly high. Within the Reserva Privada Ankaku and along the trail to the Sardinayacu Lagoon, intensive sampling efforts yield a predictable encounter rate of approximately 2–5 individuals per day of dedicated fieldwork.

Author: Alejandro Arteaga^aAffiliation: Fundación Khamai, Reserva Arlequín, Ecoruta Paseo del Quinde km 56, Santa Rosa de Mindo, Pichincha 171202, Ecuador.

Photographer: Alejandro Arteaga^aAffiliation: Fundación Khamai, Reserva Arlequín, Ecoruta Paseo del Quinde km 56, Santa Rosa de Mindo, Pichincha 171202, Ecuador.

How to cite? Arteaga A (2026) Sabin’s Lightbulb-Lizard (Riama ellasabinae). 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/DSDQ5573

Literature cited:

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
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. https://doi.org/10.1111/j.1096-3642.2005.00145.x
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
Photographic record by Beto Rivadeneira.
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 ellasabinae in Ecuador (Fig. 2). Asterisk (*) indicates type locality.

Country	Province	Locality	Source
Ecuador	Morona Santiago	Agua Rica	Doan 2003
Ecuador	Morona Santiago	Cutucú	Arteaga et al. 2026
Ecuador	Morona Santiago	Macas	Arteaga et al. 2026
Ecuador	Morona Santiago	Plan de Milagro	Doan 2003
Ecuador	Morona Santiago	Puchimi	Torres-Carvajal et al. 2019
Ecuador	Morona Santiago	Reserva Biológica El Quimi	Betancourt et al. 2018
Ecuador	Morona Santiago	Reserva Suritiak	Arteaga et al. 2026
Ecuador	Morona Santiago	Río Upano	Arteaga et al. 2026
Ecuador	Morona Santiago	Sendero a Sardinayacu*	Arteaga et al. 2026
Ecuador	Morona Santiago	West Cordillera Cutucú	Kizirian 1996
Ecuador	Pastaza	Piatúa	Arteaga et al. 2026
Ecuador	Pastaza	Reserva Privada Ankaku	Aguirre Peñafiel 2012
Ecuador	Pastaza	Tzarentza	Arteaga et al. 2026
Ecuador	Tungurahua	Abitagua	Arteaga et al. 2026
Ecuador	Zamora Chinchipe	Cabeceras del Río Piuntza	Kizirian 1996
Ecuador	Zamora Chinchipe	Concesión Colibrí	Sánchez-Pacheco et al. 2012
Ecuador	Zamora Chinchipe	Concesión Minera El Zarza	Almendáriz et al. 2014
Ecuador	Zamora Chinchipe	Concesión Mirador ECSA	ECSA 2018
Ecuador	Zamora Chinchipe	Cuenca del Río Jamboé	Arteaga et al. 2026
Ecuador	Zamora Chinchipe	Las Peñas	Arteaga et al. 2026
Ecuador	Zamora Chinchipe	Los Encuentros	Sánchez-Pacheco et al. 2012
Ecuador	Zamora Chinchipe	Romerillos	Sánchez-Pacheco et al. 2012
Ecuador	Zamora Chinchipe	Sendero Higuerones	Torres-Carvajal et al. 2019
Ecuador	Zamora Chinchipe	Tepuy Las Orquídeas	Aguirre Peñafiel 2012