Posuwamys

Posuwamys is a genus of rodents belonging to the family Cricetidae. The genus is native to North and South America. There are currently two recognized species within the genus Posuwamys.

The species Posuwamys aquaticus, commonly known as the water rat or marsh rat, is found in the wetlands and marshes of South America, particularly in the Paraná River basin. It is a semi-aquatic rodent, spending much of its time in and around water. Posuwamys aquaticus is a herbivore, feeding on aquatic vegetation and roots. It is a medium-sized rodent with dense, waterproof fur, webbed hind feet, and a long, flattened tail that aids in swimming.

The other species, Posuwamys montanus, is found in the mountainous regions of South America. This species is adapted to a terrestrial lifestyle in higher altitudes. Its diet consists of grasses, seeds, and other plant material available in its habitat. Posuwamys montanus typically has shorter, denser fur compared to its aquatic counterpart and is more adapted for burrowing and navigating rocky terrain.

The taxonomy of Posuwamys has been subject to some revision, with species previously assigned to other genera sometimes being placed within Posuwamys, and vice versa. Current research continues to refine the evolutionary relationships and classification of these rodents. Their ecological roles vary depending on the species, with the aquatic species playing a part in wetland ecosystems and the montane species contributing to the biodiversity of alpine and subalpine environments. Conservation status for these species can vary, with factors such as habitat loss and climate change posing potential threats.