This species was previously only known from just north and south of Putla de Guerrero in Oaxaca, Mexico, between 750-2,000 m asl . However, it has recently been found north of San Gabriel Mixtepec in Oaxaca, 130 km southeast of the type locality (Delia et al. 2007), and at Ejido Tres Marías from the municipality of Malinaltepec, Guerrero (García-Vázquez and Durán-Fuentes 2012). These two records greatly expand its distribution and suggest that it is very likely occurs at localities in between the known sites, especially since these regions are relatively poorly explored herpetologically (S. Rovito pers. comm. Red List Assessment Workshop 2014). Its extent of occurrence (EOO) is 6,496 km2 and its area of occupancy (AOO) is 268 km2.
Habitat and Ecology
The species is the largest tropical salamander and appears to live in permanent burrows (T. Papenfuss and D. Wake, pers. comm. 2007). Individuals have been found in a banana field and a roadside bank, suggesting some degree of tolerance to habitat disturbance. Its minimum viable population size may require a larger area of occupancy (D. Wake pers. comm. 2007). This species reproduces by direct development.
It is known only from a few specimens found on several different collection trips to the region.
The major threats for this species are urbanisation and changed agricultural practice away from shade grown coffee and increased tilling.
This species has not been recorded in any protected areas and is not protected by Mexican law.
Habitat protection is required for this species.
Further surveys are required to determine the full range of the species, and further research on its population size and trends.
Red List Status
Listed as Endangered because its area of occupancy (AOO) is 268 km2, it occurs in fewer than five threat-defined locations, and there is continuing decline in the extent and quality of its habitat.
This species was previously within the genus Pseudoeurycea but has recently been moved to Isthmura (Dubois and Raffaëlli 2012).
IUCN SSC Amphibian Specialist Group 2016. Isthmura maxima. The IUCN Red List of Threatened Species 2016: e.T61907A53989368. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T61907A53989368.en .Downloaded on 22 January 2019