DOI10.47051/FZUD8411

Published May 2, 2021. Updated December 1, 2023. Open access.

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Spotted Lightbulb-Lizard (Riama stigmatoral)

Reptiles of Ecuador | Sauria | Gymnophthalmidae | Riama stigmatoral

English common name: Spotted Lightbulb-Lizard.

Spanish common names: Lagartija minadora moteada, lagartija bombillo moteada.

Recognition: ♂♂ 13.9 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=6.3 cm. ♀♀ 11.8 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=5.9 cm..1,2 Lightbulb-lizards of the genus Riama are easily distinguished by their fossorial (burrowing) habits and extremely reduced extremities; the limbs are so short that the forelimbs and hindlimbs cannot overlap when pressed against the body.1–3 Riama stigmatoral is the sole representative of its genus within its known range. It is distinguished from its three most closely related congeners—which occur within 20 km of its distribution—by its characteristic dark brown venter featuring conspicuous pale ventrolateral spotting.1,2 In the Morona Santiago province, R. stigmatoral is the only member of the genus having an incomplete series of supraciliary scales and no lateral ocelli.1 Sexual dimorphism is prominent: adult males possess femoral pores and a broader head compared to females, and their flank spots are reddish to orange rather than pale cream (Fig. 1).

Figure showing variation among individuals of Riama stigmatoral

Figure 1: Individuals of Riama stigmatoral from the Área Ecológica de Conservación Municipal Tinajillas-Río Gualaceño Morona Santiago Province, Ecuador.

Natural history: Riama stigmatoral is a rarely observed fossorial lizard that can, however, occur in high densities within specific microhabitats of high-elevation evergreen montane forests.4 Its presence extends into anthropogenically modified areas adjacent to these forests, including pastures, trout pond clearings, and rural gardens.4 Specimens are most frequently encountered sheltered beneath logs, rocks, or debris at pasture borders, or uncovered from soft soil and root systems within mud walls at the forest edge. While specific breeding data is unavailable for this species, it is presumed that females lay clutches of two eggs beneath rocks, consistent with its closest relatives.1 These reptiles are exceptionally shy; when exposed, they retreat rapidly into the substrate. Defensive behaviors include biting or caudal autotomy (readily shedding the tail). Critically, Spotted Lightbulb Lizards are highly stenothermic and susceptible to thermal stress; they can perish quickly if exposed to direct sunlight or even from the heat transferred during prolonged handling.4

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Conservation: Vulnerable Considered to be facing a high risk of extinction in the mid-term future..5 Riama stigmatoral is categorized as Vulnerable primarily due to its highly restricted geographic range. The species’ estimated extent of occurrence is likely no greater than 800 km2, and it is currently documented from fewer than ten localities (see Appendix 1). Furthermore, there is an ongoing decline in habitat quality across its range, driven largely by deforestation and the continued expansion of the agricultural frontier.

Distribution: Riama stigmatoral is endemic to an area of approximately 620 km2 along the Amazonian versant of the Andes in Morona Santiago province, Ecuador (Fig. 2).

Distribution of Riama stigmatoral in Ecuador

Figure 2: Distribution of Riama stigmatoral in Ecuador. The star corresponds to the type locality: Pailas, 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.6–9 The specific epithet stigmatoral comes from the Greek word stigma (=spot) and the Latin noun toral (=valance), and refers to the ventrolaterally positioned spots of males of this species.1

Where to observe: Spotted Lightbulb Lizards are rarely encountered through casual observation; they are typically only recorded during targeted surveys that involve turning over rocks and logs or excavating soft soil, particularly in pastures adjacent to forest borders. In Ecuador, the most reliable locality for observing this species is the Tinajillas Conservation Area, where individuals can be found with high certainty during a dedicated single-day search.

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

Photographers: Jose VieirabAffiliation: Tropical Herping (TH), Quito, Ecuador.,cAffiliation: 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) Spotted Lightbulb-Lizard (Riama stigmatoral). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: www.reptilesofecuador.com. DOI: 10.47051/FZUD8411

Literature cited:

  1. Kizirian DA (1996) A review of Ecuadorian Proctoporus (Squamata: Gymnophthalmidae) with descriptions of nine new species. Herpetological Monographs 10: 85–155. DOI: 10.2307/1466981
  2. 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: Life in the middle of the world. Second Edition. Khamai Foundation & Tropical Herping, Quito, 1121 pp. DOI: 10.47051/MNHT9360
  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. Field notes, Reptiles of Ecuador book project.
  5. Cisneros-Heredia DF (2019) Riama stigmatoral. The IUCN Red List of threatened species. Available from: www.iucnredlist.org. DOI: 10.2305/IUCN.UK.2019-3.RLTS.T178237A54446205.en
  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.

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

CountryProvinceLocalitySource
EcuadorMorona SantiagoBetween Cerro Negro and PailasKizirian 1996
EcuadorMorona SantiagoBetween Pailas and MiradorKizirian 1996
EcuadorMorona SantiagoEl CruzadoKizirian 1996
EcuadorMorona SantiagoGuardianía TinajillasArteaga et al. 2026
EcuadorMorona SantiagoPailas*Kizirian 1996
EcuadorMorona SantiagoPiscinas de tilapiaArteaga et al. 2026
EcuadorMorona SantiagoPosada San Juan BoscoKizirian 1996