Description
Pseudoeurycea smithi is a relatively large, robust species of lungless salamander. Male snout-vent length ranges from 59 - 76 mm and females range from 52 - 88 mm. The head is large with bulging jaw muscles in many adult males with a well-defined neck; head length ranges from 12.5 - 18 mm in males and 12.0 - 17.8 in females, and head width ranges from 8.7 - 12.1 mm in males and 7.9 - 10.3 in females. Adult males have a prominent, oval mental gland on the chin (just behind mouth on underside of head). Maxillary teeth are relatively few given large size; combined premaxillary and maxillary teeth range from 21 - 45 in females and 20 - 38 in males. Male premaxillary teeth are fewer in number and are large, bifid, and pierce the lip. Vomerine teeth range from 9 - 20 in both sexes and extend in a curve beyond the outer margin of the choanae. The forelimbs are approximately 21% of snout-vent length in males and 20% in females, hind limbs approximately 23% of snout-vent length in males and 22% in females. The hands have a very short first toe, with digits in order of ascending length being I - IV - II - III; two-thirds of each digit is free of webbing. The feet have only basal webbing, with toes in order of increasing length I - V - II - IV - III. The tail is somewhat shorter than snout-vent length to slightly longer than the snout-vent length (Tail Length/Snout-vent Length ratio is 84 - 112% in males and 83 - 110% in females), constricted at base and somewhat laterally compressed, tapered along length (Taylor “1938” 1939; Canseco-Márquez and Gutiérrez-Mayén 2005; S. Rovito pers. comm.).

Pseudoeurycea smithi is larger than almost all other members of its genus; only Pseudoeurycea papenfussi (maximum snout-vent length 89.4 mm) and P. gadovii (maximum snout-vent length 83.4 mm) are similar in size. Members of the genus Isthmura are larger but are black in color with striking patterns of red or orange paired dorsal spots of chevrons (Parra-Olea et al. 2005a), which are lacking in P. smithi. The bulging jaw muscles of P. smithi are also lacking in most other species of Pseudoeurycea, with the exceptions of P. papenfussi and P. aquatica (Parra-Olea et al. 2005; Wake and Campbell 2001). Pseudoeurycea smithi lacks the extremely well defined costal grooves and musculature of P. papenfussi and has shorter limbs as well (mean hind limb length 41% and 43% of snout-vent length in males and females, respective, of P. smithi vs. 49% and 48% in males and females of P. papenfussi) (Parra-Olea et al. 2005). Pseudoeurycea gadovii has paired pale yellowish spots along the dorsum that are lacking in P. smithi. Pseudoeurycea unguidentis, like P. smithi, is relatively large (maximum snout-vent length approximately 70 mm) and has bifid premaxillary teeth in males but has a narrower head and lacks the bulging jaw musculature seen in males of P. smithi (Taylor 1941). Pseudoeurycea aquatica, known from only one stream in the Sierra Mixe (to the southeast of the distribution of P. smithi) has feet with essentially no webbing and with longer, more slender digits compared to P. smithi; additionally, it is somewhat smaller (maximum snout-vent length 70 mm) and has a flap over the external nares (Wake and Campbell 2001). All other plethodontid salamanders in Mexico are smaller and most species approaching P. smithi in size have more extensive foot webbing.

The dorsum is dark brown to dark grayish-brown, with irregular reddish-brown blotches present in some individuals; coloration can be somewhat lighter on tail compared to body. The sides of the body are greyish olive-brown with blackish bars along costal grooves, with greyish flecks sometimes present. The venter is greyish to cream with dark bars following costal grooves in some specimens (Taylor “1938” 1939; Taylor 1941; S Rovito pers comm.; Parra-Olea et al. 2005b).

This species is sexually dimorphic, with males having more robust jaw musculature and larger premaxillary teeth compared to females as well as a large, prominent mental gland. Females apparently reach a larger maximum size compared to males (88 mm vs. 76 mm snout-vent length). Both hind and forelimbs are slightly longer in males than in females (Taylor “1938” 1939; Canseco-Márquez and Gutiérrez-Mayén 2005; S. Rovito pers. comm.).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Mexico

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (3 records).

Pseudoeurycea smithi occurs only in the northern part of the state of Oaxaca, Mexico. It is known from the Sierra de Aloapaneca on Cerro San Felipe as well as from Llano de las Flores in the Sierra de Juárez, just to the north. Populations from the Sierra de Cuatro Venados, to the south of Oaxaca City, may also correspond to this species although molecular and morphological studies are needed to confirm this (Wake and Campbell 2001). It occurs at high elevations (above 2700m) in pine-oak forest; the holotype was collected approximately 200 ft (61m) from the summit of Cerro San Felipe, which reaches 3300 m elevation (Taylor “1938” 1939).

Life History, Abundance, Activity, and Special Behaviors
Adults have been found throughout the year but are presumed to be surface active only during the rainy season (approximately June to November). This species is fully terrestrial and is found under cover objects, principally logs. No details related to reproduction area available for this species. In other species of Pseudoeuryea, females guard a clutch of terrestrial eggs, typically under a cover object or inside a log. No information on the species’ diet or possible predators exists. Pseudoeuryea smithi is sympatric with Pseudoeurycea unguidentis and Thorius narisovalis on Cerro San Felipe (Taylor 1941), as well as possibly with a second species of Thorius (Thorius sp. 2; Parra-Olea et al. 2016). An undescribed species of Chiropterotriton (Chiropterotriton sp. K) occurs in the vicinity as well and may be sympatric with P. smithi (Darda 1994). At Llano de las Flores in the Sierra de Juárez, P. smithi occurs in sympatry with Thorius boreas and T. macdougalli (Hanken and Wake 1994).

Larva
The species is direct developing with no larval stage.

Trends and Threats
Pseudoeurycea smithi is classified as Critically Endangered by the IUCN with a decreasing population trend. It has an estimated Extent of Occurrence of 99 km², with populations at the type locality on Cerro San Felipe and at Llano de las Flores in the Sierra de Juárez representing a single locality in terms of threats to the species (IUCN 2020). Although quite abundant in the past, only a single individual was found in a search at the type locality on Cerro San Felipe in 1997 and no individuals have been found there subsequently, indicating that the species has declined significantly in abundance. A single individual of this species was found at Llano de las Flores in the Sierra de Juárez in 2014, indicating that the species likely still persists, at least at that locality. Habitat at both sites is in reasonably good shape, with forest cover still intact, indicating that some other factor besides habitat loss could be responsible for the species’ decline (Parra-Olea et al. 1999; Rovito et al. 2009; S. Rovito pers. comm.). A retrospective study of museum specimens that used a molecular assay to detect Batrachochytrium dendrobatidis (Bd), the fungus that is the primary cause of chytridiomycosis, found an estimated Bd prevalence of 3% in 1974 (the earliest sample of the species included in the study), 5% in 1976, and 54% 1981 on Cerro San Felipe (Cheng et al. 2011).

Relation to Humans
This species is not used by humans or traded.

Comments
Maximum likelihood analysis of portions of three mitochondrial genes (16S, cytochrome b, ND4) showed P. smithi to be most closely related to an undescribed species of Pseudoeurycea from the Sierra de Juárez, which was later described as P. papenfussi (Parra-Olea 2002). A Bayesian species tree analysis of partial mitochondrial genomes and several nuclear genes (RAG1, POMC, SLC8A3) showed this same relationship, with P. smithi and P. papenfussi as sister taxa; the group formed by these two species was sister to a clade formed by species from Oaxaca, Guerrero, and the Trans-Mexican Volcanic Belt. The sister species relationship between P. smithi and P. papenfussi was confirmed by maximum likelihood and Bayesian analysis of the concatenated mitochondrial genes as well as the concatenated mitochondrial and nuclear genes (Rovito et al. 2015).

The genus name is formed by the Latin "Pseudo," meaning "false," and "Eurycea," a genus of North American plethodontid salamanders.

The species epithet is in honor of Hobart M. Smith (1912–2013), in recognition of his many contributions to Mexican Herpetology. Dr. Smith collected the type series of this species on Cerro San Felipe, Oaxaca. Although this species was described in 1939, Dr. Smith continued to make major contributions to Mexican herpetology for many years after it was described.

References
Canseco-Márquez, L., Gutiérrez-Mayén, G. (2005). New species of Pseudoeurycea (Caudata: Plethodontidae) from the mountains of the Mixteca region of Oaxaca, Mexico. Journal of Herpetology 39, 181–185. [link]

Cheng, T.L., Rovito, S.M., Wake, D.B., Vredenburg, VT. (2011). Coincident mass extirpation of neotropical amphibians with the emergence of the infectious fungal pathogen Batrachochytrium dendrobatidis. Proceedings of the National Academy of Sciences 108, 9502–9507. [link]

Darda, D. (1994). Allozyme variation and morphological evolution among Mexican salamanders of the genus Chiropterotriton (Caudata: Plethodontidae). Herpetologica 50, 164–187. [link]

Hanken, J., Wake, DB. (1994). Five new species of minute salamanders, genus Thorius (Caudata: Plethodontidae) from northern Oaxaca, Mexico. Copeia 1994, 574–590. [link]

IUCN SSC Amphibian Specialist Group. (2020). Pseudoeurycea smithi. The IUCN Red List of Threatened Species 2020. e.T59397A53984367. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T59397A53984367.en. Accessed on 12 June 2023.

Parra-Olea, G., García-París, M., Wake, D.B. (1999). Status of some populations of Mexican salamanders (Amphibia: Plethodontidae). Revista de Biología Tropical 47, 217–223. [link]

Parra-Olea, G. (2002). Molecular phylogenetic relationships of neotropical salamanders of the genus Pseudoeurycea. Molecular Phylogenetics and Evolution 22(2), 234–246. [link]

Parra-Olea, G., García-París, M., Papenfuss, T.J., Wake, D.B. (2005). Systematics of the Pseudoeurycea bellii (Caudata: Plethodontidae) species complex. Herpetologica 61(2), 145–158. [link]

Parra-Olea, G., García París, M., Hanken, J., Wake, D.B. (2005). Two new species of Pseudoeurycea (Caudata: Plethodontidae) from the mountains of northern Oaxaca. Copeia 2005(3), 461–469. [link]

Parra-Olea, G., Rovito, S.M., García-París, M., Maisano, J.A., Wake, D.B., Hanken, J. (2016). Biology of tiny animals: three new species of minute salamanders (Plethodontidae: Thorius) from Oaxaca, Mexico. PeerJ 4, e2694. [link]

Rovito, S.M., Parra-Olea, G., Vásquez-Almazán, C.R., Papenfuss, T.J., Wake, D.B. (2009). Dramatic declines in Neotropical salamander populations are an important part of the global amphibian crisis. Proceedings of the National Academy of Sciences 106(9), 3231–3236. [link]

Rovito, S.M., Parra-Olea, G., Recuero, E., Wake, D.B. (2015). Diversification and biogeographic history of Neotropical plethodontid salamanders. Zoological Journal of the Linnean Society 175(1), 167–188. [link]

Taylor, E.H. (1939 "1938"). Concerning Mexican salamanders. University of Kansas Science Bulletin 25, 259–313. [link]

Taylor, E.H. (1941). New plethodont salamanders from Mexico. Herpetologica 2(3), 57–65. [link]

Wake, D.B., Campbell, J.A. (2001). An aquatic plethodontid salamander from Oaxaca, Mexico. Herpetologica 57(4), 509–514. [link]

Species Account Citation: AmphibiaWeb 2023 Pseudoeurycea smithi: Smith's False Brook Salamander <https://amphibiaweb.org/species/4190> University of California, Berkeley, CA, USA. Accessed Jan 7, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 7 Jan 2025.

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