Horned gopher
Horned gophers are extinct rodents from the genus Ceratogaulus, a member of the extinct fossorial rodent clade Mylagaulidae. Ceratogaulus is the only known rodent genus with horns, and is the smallest known horned mammal.[2][3] Ceratogaulus lived from the late Miocene[3][4] to the early Pliocene epochs.
The horned gopher had two horns; these were large (in comparison to body size), paired, and originated from the nasal bones. Horned gophers are the smallest known horned mammals and the only known rodents ever to have had horns.[3] They are also one of only two known horned fossorial mammals, the other being Peltephilus, an extinct species of armadillo.[3] They were native to what is now the Great Plains of North America, mostly Nebraska.
The role of the horns of Ceratogaulus is subject to much speculation. Several functions have been hypothesized (see below for a more detailed analysis) including digging, mating displays or combat, and defense from predators. The horns are not sexually dimorphic and multiple analyses support a role in defense.[2][3]
In other respects, the animals most resembled modern marmots. They were approximately 30 centimetres (0.98 ft) long, and had paddle-like forepaws with powerful claws adapted for digging. They also had small eyes, and probably had poor eyesight, similar to that of a mole. These features, and some formal analyses of their morphology,[5] suggest that they were likely burrowing animals.[4]
The nasal horns of Ceratogaulus are inconsistent with use as a digging tool. In recent mammals that use their heads for excavating, the tips of their snouts are used like a spade to scrape at the substrate. Therefore, the only modification of the nasal bones is a slight thickening of the anterior tips. Although it is theoretically possible that some mammal might develop horns as a digging tool, digging horns would differ from the Ceratogaulus horns in position and shape.[3]
Ceratogaulus horns are positioned on the posterior ends of the nasal bones and extend dorsally, perpendicular to the plane of the palate. As a result of their posterior position, using the horns to dig would bring the anterior tip of the nasals against the substrate after a very short sweep of the horns, making digging with the horns extremely inefficient. This motion would be even more inefficient than suggested because the anterior surface of a burrow is concave, making it essentially impossible to use the horns without the anterior end of the snout interfering. The expectation is that an animal using its horns anteriorly (rather than dorsally) would have the occipital plate positioned vertically or tilted posteriorly. In this configuration, the effective input lever is maximized when the head is lowered, as in the rhinoceros skull.[3]
