Thorius narismagnus Shannon & Werler 1955

This is a small species; adult standard length averages 18.3 mm in 10 males (range 16.6-20.8) and 17.8 mm in 4 females (range 16.7-19.2). The head is relatively broad; SL averages 6.7 times head width in males (range 6.0-7.6), 6.5 times head width in females (range 6.0-7.1). Snouts are relatively broad and blunt in females and more pointed in males. Nostrils are relatively large and nearly round; the mean ratio of major axis to minor axis equals 1.1 in both males (range 1.0-1.2) and females (range 1.0-1.1). Eyes are moderately sized and protrude slightly beyond the margin of the head in ventral view. A suborbital groove intersects the lip on each side of the head. The two males each have a single premaxillary tooth, 4-5 vomerine teeth, and no maxillary teeth. There were no cleared-and-stained female specimens on which to count teeth. Limbs are relatively long and slender; limb interval averages 3.4 in males (range 2-4) and 3.8 in females (range 3-4). Hands and feet are narrow; the third finger and toe are substantially longer than remaining digits and are sharply pointed. Fingers, in order of decreasing length, are 3-2-4-1; toes are 3-4-2-5-1. The tail is relatively long; mean SL divided by tail length equals 0.68 in males (range 0.64-0.80) and 0.72 in females (range 0.67-0.76). The mental gland is round to ovoid. The postiliac gland is obscure (Hanken and Wake 1998).

Thorius narismagnus is disjunct from all congeners. It is known only from the forested slopes of Volcán San MartÌn, in the Sierra de Los Tuxtlas, Veracruz, Mexico. Recorded elevations range from 890 to 1200 m. It is an exclusively terrestrial species; according to field notes by J. Hanken (7 Feb. 1976), specimens were collected from under rotten logs and among leaf litter on the forest floor, especially under fallen bromeliads (Hanken and Wake 1998).

Thorius narismagnus is a species of salamander in the family Plethodontidae. It is endemic to the San Martin Tuxtla volcano, in the Sierra de los Tuxtlas range in southern Veracruz state, Mexico. Its common name is San Martin pigmy salamander. Natural habitats of Thorius narismagnus are lowland and intermediate tropical forests. It occurs under rotten logs and among leaf-litter, and especially under fallen bromeliads.

This species had not been seen since 1970s, until it was rediscovered in 2012. It has suffered from habitat loss, but this might not suffice to explain the disappearance of this species.