The genus Microcavia is composed of five species, four of which are found in Argentina. Of these last four, three geographically allopatric morphotypes were recently recognized—previously considered as M. Australis (Teta, 2017). They differ in size and general cranial shape, among other traits. All three are elevated to the status of full species:

M. maenas (Thomas, 1898): up to 2500 meters above sea level, in mountainous regions of Catamarca, La Rioja, Salta, San Juan, and Tucumán; also in low and arid lands, in O Córdoba, C-N Mendoza, and N San Luis. Larger size (20.3 cm in length); dorsal coloration variable, ranging from yellowish gray to brown, depending on the specimen, with undersides ranging from grayish to yellowish; broad skull, larger than in the other species of the genus, with a slightly arched dorsal profile.

M. australis (I. Geoffroy and d’Orbigny, 1833): from the west of Argentina, in S Mendoza (>2000 meters above sea level) and eastward, in S-O Buenos Aires; southward to Santa Cruz, and also in adjacent parts of S Chile. Some puna populations from S San Juan could correspond to this species, at least judging by their size and cranial morphology. Medium size, slightly larger than M. Jayat (18.8 cm in length); dorsal coloration ranging from brown to olive green, with undersides from gray to yellowish gray; broad and relatively short skull, with a strongly inclined dorsal profile.

M. jayat (Teta, Ojeda, Lucero et D´Elía, 2017): restricted to thorny forests and shrublands of the Chaco Seco ecoregion in Santiago del Estero (with a likelihood of being present in the Chaco forests of nearby provinces: Salta, Chaco, Córdoba, and Santa Fe). Medium size (18.7 cm in length); features white hair spots on the throat and the inner sides of the front and rear parts of the feet, as well as on the inguinal region; broad and relatively short skull, with moderately arched dorsal profile.

The other species present in Argentina is M. shiptoni (Thomas, 1925), which inhabits grasslands and shrublands between 3000 and 5000 meters above sea level in the northwest of Argentina, in the provinces of Salta, Tucumán, and Catamarca. It is small, slightly smaller than the other species (18 cm in length). Its fur is finer and less mottled, with pale tawny dorsal coloration and light brownish-yellow coloration on the belly. The ears are dark and have more fur (Canevari and Vaccaro, 2007). Its conservation status is listed as ´Near Threatened´ (SAREM, 2012).

The remaining species of the genus, M. niata (Thomas, 1898), is found in the high plateau of Bolivia, Chile, and Peru (Zeballos et al., 2018).

The identification of each of these species is more accurately based on discrete and constant differences in the zygomatic arch, palate, and mesopterygium fossa, as well as in the size and shape of the skull. For this reason, it is recommended that when recording any of the species outside of the distribution ranges mentioned here, the identification should be supported by skeletal material collected from the recording area. Other useful data may be provided through variables such as environment, altitude, habitat, ecoregion, age, wear, etc.

Regarding the differences compared to other genera within the Caviinae subfamily in our country, it can be broadly stated that Galea appears more robust with a more pronounced neck compared to Microcavia, while Cavia is the largest of all, lacking a convex forehead and ocular ring (sometimes only faintly marked and yellowish in color).

Key for identifying genera within the Caviinae subfamily (Cabrera, 1953):

Entirely hairy interramal region; white incisors; anteorbital bridge with the edge formed solely by the maxilla ==> 3

Interramal region with a bare space in the center; yellow incisors; anteorbital bridge with the edge partly made of lacrimal bone ==> Galea.

3.1. Ears with well-developed tragus and antitragus; molars without cement intercalations between their prisms; pm4 with an accessory anterior extension in the first prism ==> Microcavia.
3.2. Ears with atrophied tragus and antitragus; molars with folds between the prisms filled with cement; pm accessory anterior extension in the first prism without elongation ==> Cavia.

Author of this compilation: Román Montero

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