DOI10.47051/VRFJ2435

Published December 17, 2020. Updated April 4, 2026 Open access. Peer-reviewed.

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Günther’s Sun Tegu (Euspondylus guentheri)

Reptiles of Ecuador | Sauria | Gymnophthalmidae | Euspondylus guentheri

English common name: Günther’s Sun Tegu.

Spanish common name: Lagartija tegú de Günther.

Recognition: ♂♂ 24.9 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=9.4 cm. ♀♀ 22.8 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=8.4 cm..1–3 Species of the genus Euspondylus are distinguished from similar arboreal microteiids (such as Anadia, Cercosaura, and Selvasaura) by their smooth or striated rectangular dorsal scales, flank scales smaller than the dorsals, and the absence of a pale vertebral stripe.1,4 The Günther’s Sun Tegu (E. guentheri) differs from its only Ecuadorian congener, E. maculatus, primarily in coloration. Adults feature a dorsal pattern of irregular black crossbars or blotches on a lighter background, while juveniles exhibit a striking pattern of black crossbars on a bright yellowish ground color.1–3 While some Anadia petersi possess similar black dorsal blotches, they can be distinguished by a dark brown lateral stripe, which is absent in E. guentheri. Additionally, Cercosaura species have granular scales on the side of the neck, whereas these scales are large and plate-like in Euspondylus.4

Figure showing variation among individuals of Euspondylus guentheri

Figure 1: Individuals of Euspondylus guentheri from Ecuador: Cabeceras del Bobonaza, Pastaza province, (); unknown locality ().

Natural history: Euspondylus guentheri is an extremely rare, primarily diurnal, and arboreal lizard. It inhabits old-growth and moderately disturbed evergreen lowland and foothill forests, though it occasionally ventures near human settlements.5 Individuals have been observed basking at ground level among roots and leaf litter, or moving on branches approximately 1 m above the forest floor.5,6 One nocturnal observation involved an individual active on a muddy wall inside the forest.3 When inactive, they hide under fallen branches, beneath thick leaf litter, or among woody fungi on tree bark up to 2 m high.3,7,8 When threatened, they flee quickly into cover; if captured, they may bite aggressively or readily autotomize (shed) the tail.3,8

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Conservation: Least Concern Believed to be safe from extinction given current circumstances..9 Euspondylus guentheri is categorized as Least Concern because its range retains the majority of its original forest cover and the species is considered to be facing no immediate widespread extinction threats.9,10 It occurs in at least seven protected areas in Ecuador and Colombia. However, habitat destruction from mining and agricultural expansion remains a long-term threat.

Distribution: Euspondylus guentheri is native to an area of approximately 55,971 km2 along the Amazonian foothills of the Andes in Ecuador and Colombia (Fig. 2).

Distribution of Euspondylus guentheri in Ecuador

Figure 2: Distribution of Euspondylus guentheri in Ecuador. See Appendix 1 for a complete list of the presence localities included in the map.

Etymology: The generic name Euspondylus, which is derived from the Greek words eu (=easy) and spondylos (=vertebra),11 probably refers to the ease with which the caudal vertebrae in lizards of this genus can become detached to allow the shedding of the tail. The specific epithet guntheri honors Albert Günther (1830–1914), a German-born British zoologist, ichthyologist, and herpetologist, best known for his role as Keeper of Zoology at the Natural History Museum in London.

Where to observe: As one of the rarest lizards in the Amazon, only 30 sightings have ever been reported (11 museum specimens and 19 photographic records). While sightings at Río Bigal Biological Reserve have occurred more than once, they remain opportunistic. The probability of an encounter may increase by searching through thick, damp leaf-litter or turning over rocks and logs in suitable habitats.

Acknowledgments: Special thanks to Alexis Barahona, Danilo Media, Jorge Flores, José Simbaña, and Thierry García for providing locality and natural history data of Euspondylus guentheri. 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.

Photographer: Jose VieiracAffiliation: Tropical Herping (TH), Quito, Ecuador.,dAffiliation: ExSitu, Quito, Ecuador.

How to cite? Arteaga A (2026) Günther’s Sun Tegu (Euspondylus guentheri). 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/VRFJ2435

Literature cited:

  1. Chávez G, Catenazzi A, Venegas PJ (2017) A new species of arboreal microteiid lizard of the genus Euspondylus (Gymnophtalmidae: Cercosaurinae) from the Andean slopes of central Peru with comments on Peruvian Euspondylus. Zootaxa 4350: 301–316. DOI: 10.11646/zootaxa.4350.2.6
  2. Boulenger GA (1885) Catalogue of the lizards in the British Museum. Taylor & Francis, London, 497 pp.
  3. Field notes, Reptiles of Ecuador book project.
  4. Peters JA, Donoso-Barros R (1970) Catalogue of the Neotropical Squamata: part II, lizards and amphisbaenians. Bulletin of the United States National Museum, Washington, D.C., 293 pp.
  5. Danilo Medina, pers. comm.
  6. Jose Simbaña, pers. comm.
  7. Thierry García, pers. comm.
  8. Alexis Barahona, pers. comm.
  9. Lehr E, Doan TM (2016) Euspondylus guentheri. The IUCN Red List of threatened species. Available from: www.iucnredlist.org. DOI: 10.2305/IUCN.UK.2016-1.RLTS.T178658A50867804.en
  10. MAE (2012) Línea base de deforestación del Ecuador continental. Ministerio del Ambiente del Ecuador, Quito, 30 pp.
  11. 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 Euspondylus guentheri in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used.

CountryProvinceLocalitySource
ColombiaCaquetáLa Tortuga ReserveiNaturalist; photo examined
ColombiaPutumayoReserva Fin del MundoPhoto by Jose Vicente Rodríguez
ColombiaPutumayoReserva Natural Tunel del Dragón VerdeiNaturalist; photo examined
ColombiaPutumayoYunguillo, 5 km E ofiNaturalist; photo examined
EcuadorMorona SantiagoChiguazaKöhler & Lehr 2004
EcuadorMorona SantiagoMacumaUIMNH 65696; VertNet
EcuadorMorona SantiagoValle del Río QuimiBetancourt et al. 2018
EcuadorNapoCascadas del Río HollíniNaturalist; photo examined
EcuadorNapoChallwa Yaku, 2 km N ofiNaturalist; photo examined
EcuadorNapoColonso Chalupas Biological ReserveAlexis Barahona, pers. comm.
EcuadorNapoNarupayacuPhoto by José Simbaña
EcuadorNapoWild Sumaco Wildlife SanctuaryCamper et al. (2021)
EcuadorOrellanaReserva Biológica Río BigalPhoto by Thierry García
EcuadorPastazaAlto CurarayKöhler & Lehr 2004
EcuadorPastazaCabeceras del Río BobonazaThis work; Fig. 1
EcuadorPastazaCentro de Rescate YanacochaReptiles of Ecuador book database
EcuadorPastazaMazaramuOrtega-Andrade 2010
EcuadorPastazaMontalvoPeters 1959
EcuadorPastazaPindoyacuOrtega-Andrade 2010
EcuadorPastazaPuyoPhoto by Danilo Medina
EcuadorPastazaRío LliquinoKöhler & Lehr 2004
EcuadorPastazaSantanaKöhler & Lehr 2004
EcuadorPastazaSarayacu*O’Shaughnessy 1881
EcuadorPastazaTamandúa ReserveiNaturalist; photo examined