Thorius minydemus
Minute Thorius
family: Plethodontidae
subfamily: Hemidactyliinae

© 2009 Sean Michael Rovito (1 of 4)
Conservation Status (definitions)
IUCN (Red List) Status Critically Endangered (CR)
Other International Status None
National Status None
Regional Status None


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The description of Hanken and Wake (1998) is based primarily on data from two adult males (MVZ 131444, the holotype, and UIMNH 21816) and one female (UIMNH 21818). Complete measurements could not be obtained from the remaining paratypes, which are poorly preserved. Although very small, this species is characterized by a relatively robust habitus; adult standard length averages 18.2 mm in males (range 17.1-19.2) and 21.3 mm in the female. The head is relatively broad; SL averages 6.6 times head width in males (range 6.4-6.8) and is 6.9 times head width in the female. The snout is bluntly pointed in the female and more sharply pointed in males. Nostrils are relatively large and round to slightly oval; the mean ratio of major axis to minor axis equals 1.2 in males (range 1.1-1.2) and 1.3 in the female. Eyes are relatively large and protuberant; their outline extends beyond the margin of the head in dorsal view. A suborbital groove intersects the lip on each side of the head. There are 1-2 premaxillary teeth in males (mean 1.5) and 3 in the female. Vomerine teeth average 5.5 in males (range 5-6); there are 9 in the female. A moderate number of maxillary teeth (19) are present in the female; males have few or no teeth (range 0-3). Limbs are relatively long and slender; limb interval averages 3.5 in males (range 3-4) and is 4.0 in the female. Hands and feet are very small; the hand is so short and narrow as to be barely distinguishable from the distal limb. Toes are distinct; all are free or partly free at their tips. The third finger and toe are sharply pointed and much longer than adjacent digits, which are bluntly pointed. The fourth finger and fifth toe are barely distinguishable externally. Fingers, in order of decreasing length, are 3-2-4-1; toes are 3-2-4-1-5. The tail is relatively short and stout in males; mean SL divided by tail length equals 1.07 (range 1.03-1.10). The tail is missing from the female specimen. Coloration of paratypes appears to resemble that of the holotype (dark with a dorsal stripe and ventral white spotting), although some specimens are faded. The iris is very dark brown to black. The mental gland is relatively large and ovoid. The postiliac gland is barely perceptible (Hanken and Wake 1998).

General coloration dark brown with a lighter brown dorsal stripe. Lower flanks dark brown speckled with white. Ventral parts lighter, with a network of white spots (Raffaëlli 2007).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Mexico


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The type series of Thorius minydemus is from the vicinity of the village of La Joya, Veracruz, Mexico, ca. 21 km NW of the city of Jalapa and 3 km E of the town of Las Vigas. Recorded elevation for La Joya varies between 2,100 and 2,250 m. Based on field notes of D. B. Wake (23 Oct. 1981): The type locality is at the lower elevational range of mixed pine-oak forest in this region. It is a marginal cloud forest, consisting of oaks and pines growing on poor soil in an area of extensive lava flows. Bromeliads are abundant, especially in the oaks. Two additional specimens are referred to this species, KU 26140 and 26159. Both were collected by W. W. Dalquest from Las Vigas, elev. 8500 ft, 16 Oct. 1948. While Las Vigas is the principal locality for T. munificus, there is no indication from our own field experience that this species and T. minydemus occur in sympatry. The exact collection locality of Dalquest's specimens is unknown (Hanken and Wake 1998).

Life History, Abundance, Activity, and Special Behaviors
Presumably reproduces by direct development (Stuart et al. 2008).

Trends and Threats
This species is rare and is a micro-endemic, with a very restricted and fragmented range (Stuart et al. 2008. It is under significant threat from habitat loss and alteration due to logging, mining, agriculture, livestock grazing, and human settlement (Stuart et al. 2009). It does not occur within any protected areas (Ochoa-Ochoa et al. 2009; Stuart et al. 2008). One locality, Cerro Loma Alta, had been almost completely destroyed as of 2003, due to logging and invasive plants, and no salamanders were found there (Stuart et al. 2008). At another locality, La Joya, only about 15 ha of habitat were still available as of 2004, with the surrounding area severely disturbed by both logging and mining (Stuart et al. 2008). As of November 2009 this species was still present at La Joya (S. M. Rovito, pers. comm.).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Habitat fragmentation

The species name, used as an adjective, is a conjunction of two Greek words, minys (small) and demas (body, frame), in reference to the extremely tiny adult body size of these animals, which are small even in comparison to most other Thorius (Hanken and Wake 1998).


Hanken, J. and Wake, D. B. (1998). ''Biology of the tiny animals: Systematics of the minute salamanders (Thorius: Plethodontidae) from Veracruz and Puebla, Mexico, with descriptions of five new species.'' Copeia, 1998(2), 312-345.

Ochoa-Ochoa, L., Urbina-Cardona, J. N., Vázquez, L.-B., Flores-Villela, O., and Bezaury-Creel, J. (2009). ''The effects of governmental protected areas and social initiatives for land protection on the conservation of Mexican amphibians.'' PLoS One, 4(9), e6878.

Raffaëlli, J. (2007). Les Urodèles du monde. Penclen Edition, France.

Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., and Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.

Written by David B. Wake (wakelab AT, Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720
First submitted 2000-11-08
Edited by Kellie Whittaker (2010-01-10)

Species Account Citation: AmphibiaWeb 2010 Thorius minydemus: Minute Thorius <> University of California, Berkeley, CA, USA. Accessed Oct 21, 2017.

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Citation: AmphibiaWeb. 2017. <> University of California, Berkeley, CA, USA. Accessed 21 Oct 2017.

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