The genus was endemic to North America during the Late Oligocene to Early Miocene (33.9—16.3 mya) and lived for approximately 17.6 million years.

[1] Because the eyes and nostrils were placed high on the head, it was long assumed that Leptauchenia was an aquatic, or semi-aquatic animal.

However, because their fossils have never been found in floodplain deposits or river channels, and their abundance in fossil sand dunes, Donald Prothero suggests that they were desert-dwelling animals.

Skeletons of Leptauchenia have been found by the thousands and in greater numbers than the related genus Sespia, it is often quoted as being the most numerous mammal in North America during the Late Oligocene.

Dental microwear suggests that L. decora was a regional mixed feeder.