Amynodontidae

Amynodontidae is an extinct family of rhinocerotoids, known from the Eocene to Oligocene of North America, Europe, and Asia. They were among the dominant groups of herbivorous mammals in the Northern Hemisphere, and were most diverse in Asia. Most amynodonts had a somewhat hippopotamus-like build, with massive bodies, short and robust limbs, and tusk-like canine teeth. They have been nicknamed swamp rhinoceroses due to historically being interpreted as semiaquatic; modern research suggests that only some members of the group had semiaquatic lifestyles.

Derived amynodonts are generally grouped into the lightly built and terrestrial tapir-like cadurcodontines and the semiaquatic metamynodontines. Amynodonts increased in body size over the course of their evolutionary history, and ranged in weight from just over a hundred kilograms ("Amynodon" sinensis) to close to three tonnes (Zaisanamynodon).

Description

Amynodonts had several hippopotamus-like features, such as massive bodies and short, robust limbs. They were medium-sized to large animals. It was traditionally believed that the entire family was adapted to semiaquatic life, but different amynodonts are now known to have been adapted to different lifestyles. The derived metamynodontines had clear adaptations towards a semiaquatic lifestyle but the other group of derived amynodonts, the cadurcodontines, were more lightly built and terrestrial, probably similar to modern tapirs.