Archaeomeryx is an extinct genus of ruminant that lived early in the Eocene. It is believed to be close to the ancestry of modern-day deer from had fully functioning sharp front teeth. It was also very small in size, comparable to a modern-day mouse. It was also very rabbit-like and had several distinctive characteristics. It lived in present-day China 35 to 40 million years ago. Over the years, it eventually lost its front teeth and eventually evolved into modern-day deer.