Physalaemus petersi (Jiménez de la Espada, 1872) Eupemphix paraensis Müller, 1923 Eupemphix schereri Myers, 1942 Engystomops petersi (common name: Peters' dwarf frog) is a species of frog in the family Leptodactylidae.

Taxonomy and classification of this species is constantly changing due to the continual evolution of behavioral isolation and rapid speciation in the region.

Its oral disc is filled with small papillae arranged rows with various tip lengths and shapes.

A distinguishing characteristic of E. petersi larvae compared to other Engystomops species is the presence of prominent elliptical paravertebral glands.

While they are terrestrial, they breed near water bodies, specifically on the edges of lakes, ponds, and pools.

[1] The genus Engystomops is a lineage of frogs located in the Andean foothills of Ecuador, Peru, and Bolivia, extending to the Amazon basin in Brazil.

Its karyotype is unique compared to other Engystomops species in the area and specifically diverges from the southwestern clade known as E. freibergi located in southern Peru and Brazil.

[9] In a herpetological study in Bolivia, E. petersi were observed feeding on termites in a semicircular formation.

[5] E. petersi females display preferential mate selection towards males with conspecific calls.

In certain areas E. petersi populations also add a suffix to the end of the whine that occurs at a higher frequency compared to the rest of the call.

[10] The strong preference for local males serves as evidence of behavioral isolation in this species.

The rapid speciation of E. petersi makes it a good subject for analysis of evolutionary patterns in these environments.

This has led to hybrid specification with minimal phenotypic differences between frogs in close geographic proximity.

[11] This has been attributed to high variation in chromosome structure, banding pattern, and length between the different species creating unstable karyotypes in future progeny.

[12] They are potentially threatened by the invasive species of rainbow trout that has infested the water of the Ecuadorian Andes.

Rainbow trout serve as a vector for Saprolegnia diclina, which can effectively transmit this disease to E. petersi tadpoles, increasing their mortality and iltuimately contributing to the decrease of anuran populations in the area.

Since E. petersi is localized to a comparatively small region, such habitat loss could be especially devastating for this species.