A New Species of Heteromyid Rodent from the Middle Oligocene of Northeast Colorado with Remarks on the Skull

Listeners are taken on a meticulous field adventure to the Oligocene strata of Logan County, Colorado, where a 1946 expedition uncovered the partial skull of an unfamiliar heteromyid rodent. The find, a new species larger than any previously recorded, adds a missing piece to the puzzle of early rodent evolution, offering a rare glimpse into the anatomy that once defined these small mammals.

The description walks through the skull’s distinctive features: a deep, laterally‑compressed rostrum, a unique arrangement of cusps on the fourth premolar, and a set of undivided internal cingula that rival those of modern relatives like Liomys. Detailed plates accompany the narration, highlighting dorsal, lateral, and ventral views that reveal the subtle blend of heteromyid and geomyid traits. Comparisons with both fossil and living species illustrate how this specimen confirms that key heteromyid characteristics were already established by the middle Oligocene.

In this concise scientific tale, listeners will grasp the excitement of discovery, the careful anatomy that underpins taxonomy, and the broader story of North American rodent history—delivered in clear, engaging language.