Toxodon (Gr. τόξον, a bow, and όδούς,, a tooth), a name applied by Owen to a genus of extinct mammals of the order of ungulates, with affinities to edentates and rodents. The first species, named by Owen the T. Platensis, was found in a miocene clay in South America, about 120 m. N. W. of Montevideo; it was established on a cranium 21/3 ft. long, elongated, with a flattened occiput, small cerebral cavity, remarkably strong and widely expanded zygomatic arches, and transverse glenoid cavity; the upper molars were seven on each side, implanted with the convexity outward, the opposite of what occurs in rodents; they were long, arched, without roots, the enamel forming an irregular prismatic grooved tube; upper incisors four, the external the largest, like those of rodents in structure, and worn away in the same chisel shape; in the lower jaw were seven molars on a side, and six incisors ranged in a semicircle; the name was derived from the curve of the outer upper incisors. It was large, low on the legs, with the aspect and habits of a pachyderm.
It shows an affinity to the sire-nia (like the manatee) in the flattened occiput, small brain cavity, and nasal passages widely opened above, but differs in the size of the frontal sinuses and in the incisors; it seems to have formed a connecting link between the rodents and the ungulates. It was probably aquatic to a certain extent. - See " Fossil Mammals of the Voyage of the Beagle," described and figured by Prof. Owen (4to, London, 1840).