Published November 9, 2020. Updated June 11, 2024. Open access.

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Black Thread-Snake (Trilepida anthracina)

Reptiles of Ecuador | Serpentes | Leptotyphlopidae | Trilepida anthracina

English common names: Black Thread-Snake, Baños Earthworm-Snake, Bailey's Blind-Snake.

Spanish common names: Culebra lombriz negra, serpiente gusano del Pastaza, culebra ciega.

Recognition: ♂♂ 29.3 cmMaximum distance from the snout to the tip of the tail. ♀♀ 28 cmMaximum distance from the snout to the tip of the tail.. In its area of distribution, Trilepida anthracina can easily be recognized by its small size, rudimentary eyes, and fossorial habits.1 This species differs from Amerotyphlops reticulatus by having three supralabial scales and by lacking a whitish snout (Fig. 1). Other identifying features of T. anthracina include ventral scales similar in size to dorsal scales, and left lung absent.1

Juvenile of Trilepida anthracina

Figure 1: Juvenile of Trilepida anthracina from San Pedro, Tungurahua province, Ecuador.

Natural history: Trilepida anthracina is an extremely rare fossorial snake that inhabits old-growth to moderately disturbed evergreen montane forests and cloud forests. It also occurs in areas containing a matrix of pastures, crops (particularly of naranjilla), rural houses, gardens, and remnants of native vegetation.2,3 Black Thread-Snakes spend most of their lives in tunnels they excavate in areas of soft soil or under rocks, logs, or in leaf-litter.2,4 Individuals have also be seen moving at ground level during the day,2,3 basking on the forest floor,5 or crossing roads and trails.3 There is no published information about the diet or reproduction of T. anthracina. If handled, individuals usually just try to flee, but they can also use their sharp tail tip for poking.

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Conservation: Vulnerable Considered to be facing a high risk of extinction in the mid-term future..6 Trilepida anthracina is included in this category based on the species’ limited confirmed extent of occurrence and because there is continuing decline in the extent and quality of its habitat.6 Although there are records of T. anthracina in extreme southeastern Ecuador,4,5 it is still unsure if these in fact belong to the same species as the individuals in the Pastaza river valley. In this valley, Black Thread-Snakes have been registered in two private reserves (Chamana and La Candelaria),7 but the majority of the individuals have been seen in areas suffering from intense deforestation.

Distribution: Trilepida anthracina is endemic to an area of approximately 11, 662 km2 along the Amazonian slopes of the Andes of Ecuador (Fig. 2).

Distribution of Trilepida anthracina in Ecuador

Figure 2: Distribution of Trilepida anthracina in Ecuador. The star corresponds to the type locality: Baños, Tungurahua province. See Appendix 1 for a complete list of the presence localities included in the map.

Etymology: The name Trilepida is derived from the Greek words treis (=three) and lepis (=scale),8 referring to the presence of three supralabial scales, a characteristic that separates snakes of this genus from other blind snakes.1 The specific epithet anthracina is derived from the Latin word anthrakinus (=coal-black),9 referring to the blackish coloration.10

See it in the wild: Black Thread-Snakes are recorded accidentally at a rate of about once every few months along the valley of the Río Pastaza in Tungurahua province. One way to increase the odds of finding individuals is by actively digging in areas of soft soil or by turning over rocks and logs along forest edge habitats.

Acknowledgments: Special thanks to Darwin Núñez, David Salazar, and Maritza Copo for providing natural history information and locality records for Trilepida anthracina. Thanks to María Jose Quiroz for finding the individual of Trilepida anthracina photographed in this account.

Special thanks to Oliver Levers for symbolically adopting the Black Thread-Snake and helping bring the Reptiles of Ecuador book project to life.

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Author: Alejandro ArteagaaAffiliation: Khamai Foundation, Quito, Ecuador.

Photographer: Jose VieiraaAffiliation: Tropical Herping (TH), Quito, Ecuador.,bAffiliation: ExSitu, Quito, Ecuador.

How to cite? Arteaga A (2020) Black Thread-Snake (Trilepida anthracina). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/YZRY9660

Literature cited:

  1. Adalsteinsson SA, Branch WR, Trape S, Vitt LJ, Hedges SB (2009) Molecular phylogeny, classification, and biogeography of snakes of the Family Leptotyphlopidae (Reptilia, Squamata). Zootaxa 2244: 1–50. DOI: 10.11646/zootaxa.2244.1.1
  2. Field notes, Reptiles of Ecuador book project.
  3. Maritza Copo, pers. comm.
  4. Salazar-Valenzuela D, Carrillo EO, Aldás A S (2010) Tricheilostoma anthracinum. Geographic distribution. Herpetological Review 41: 111–112.
  5. Darwin Núñez, pers. comm.
  6. Reyes-Puig C (2019) Trilepida anthracina. The IUCN Red List of threatened species. Available from: DOI: 10.2305/IUCN.UK.2019-3.RLTS.T203643A2769326.en
  7. Marco Reyes-Puig, pers. comm.
  8. Hedges SB (2011) The type species of the threadsnake genus Tricheilostoma Jan revisited (Squamata, Leptotyphlopidae). Zootaxa 3027: 63–64. DOI: 10.11646/zootaxa.3027.1.7
  9. Brown RW (1956) Composition of scientific words. Smithsonian Books, Washington D.C., 882 pp.
  10. Bailey JR (1946) Leptotyphlops anthracinus, a new blind snake from eastern Ecuador. Occasional Papers of the Museum of Zoology, University of Michigan 492: 1–5.

Appendix 1: Locality data used to create the distribution map of Trilepida anthracina in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used. Asterisk (*) indicates type locality.

EcuadorNapoCocodrilos, 1 km SW ofMedrano-Vizcaíno et al. 2023
EcuadorPastazaAbitaguaBailey 1946
EcuadorTungurahuaAlong Ulba riverReptiles of Ecuador book database
EcuadorTungurahuaBaños*Bailey 1946
EcuadorTungurahuaParque de la FamiliaReptiles of Ecuador book database
EcuadorTungurahuaReserva La CandelariaReyes-puig et al. 2013
EcuadorTungurahuaReserva La ChamanaReptiles of Ecuador book database
EcuadorTungurahuaSan PedroThis work; Fig. 1
EcuadorTungurahuaVía a PuntzanReptiles of Ecuador book database
EcuadorZamora ChinchipeTepuy Las OrquídeasDarwin Núñez, pers. comm.
EcuadorZamora ChinchipeTundayme, 6.5 km SE ofSalazar-Valenzuela et al. 2015