The ancient bison (Bison antiquus) lived from about 240,000 to 10,000 years ago, according to the National Park Service (NPS). It was 25% larger than the modern American bison (Bison bison), at 7.5 feet (2.3 m) high, 15 feet (4.6 m) long and 3,500 pounds (1,600 kg). Its horns were also longer than those of modern bison. These herbivores are likely ancestral to American bison, according to the NPS. Have you ever seen an American bison in its natural habitat?

In 1980, researchers found the near-complete remains of Gomphotaria pugnax (ancient walrus) — a now-extinct giant pinniped — in Southern California. G. pugnax lived about 8.5 million to 5 million years ago, during the late Miocene epoch, the scientists reported in the journal Contributions In Science. Its large 18.5-inch-long (47 cm) skull had large upper and lower canine tusks. It was built more like a sea lion than a modern walrus, but featured tusks reminiscent of its extant relatives. Curiously, it also had two lower, forward-facing tusks. These were probably used to break open shellfish. The ancient walrus likely swam in shallow waters and used these tusks to stir up sediment on the seafloor while searching for food, most likely hard-shelled invertebrates such as mollusks. Have you ever visited an area where there were walruses?