The Cenozoic Era, which is often described as the “Age of Mammals,” began 65 million years ago. Following the disappearance of the dinosaurs, mammals proliferated in number, size, and diversity. The Los Angeles County Natural History Museum has a gallery devoted to The Age of Mammals.
Shown below are the extinct wolves, dogs, cats, and bears which are shown in this gallery.
Canis dirus
The dire wolf is one of the largest wolf species. Dire wolves ranged throughout North America from 500,000 to 10,000 years ago. These wolves, like today’s gray wolves, probably hunted in packs.
According to the Museum display:
“In many types of mammals, males have a bone called the baculum in their penis. Females may have a similar but smaller bone.”
Epicyon haydeni
This large dog was common in western North America from 10 million years ago until 5 million years ago. It was a carnivore whose skull and teeth were adapted for crushing bones.
Smilodon fatalis
California has a state fossil: the saber-toothed cat. This predator was like a lion in size and a tiger in build. According to the Museum display:
“It was probably an ambush predator, leaping on its prey from cover. It was widely distributed in North and South America during the Ice Age. Smilodon evolved from the dirk-toothed cats that migrated from Eurasia to North America about 5 million years ago. Smilodon outlasted its Eurasian relatives but became extinct about 11,000 years ago.”
Panthera atrox
This large cat, often called the American lion, is closely related to the jaguar. Giant jaguars migrated from Eurasia to the Americas toward the end of the Ice Age. It became extinct about 11,000 years ago.
Bears
The short-faced bear (Arctodus simus) was widely distributed throughout both North and South America. It was one of the largest land carnivores during the Pleistocene. According to the Museum display:
“Unlike most bears, this mammal lived almost exclusively on meat, running down its prey or scavenging from other predators. Its closest living relative is the spectacled bear from South America.”
About 50,000 years ago, the grizzly bear (Ursus arctos) arrived in Alaska from Siberia. Grizzlies did not move south of the ice sheets until the end of the Pleistocene.
During the early Pleistocene, black bears (Ursus americanus) arrived in North America. Black bears are omnivores.
Paleontology
Paleontology is the study of the ancient past through fossil remains. In his book The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design, Richard Dawkins writes:
“Paleontology is the study of fossils. It is a very important branch of biology, because evolutionary ancestors all died long ago and fossils provide us with our only direct evidence of the mammals and plants of the distant past. If we want to know what our evolutionary ancestors looked like, fossils are our main hope.”
More from this series:
Paleontology 101: Brontotheres (Photo Diary)
Paleontology 101: The Paleozoic (Photo Diary)
Paleontology 101: The Cenozoic--The Age of Mammals (Photo Diary)
Paleontology 101: The Mesozoic--The Age of Dinosaurs (Photo Diary)
Paleontology 101: Dinosaur Hall (Photo Diary)
Paleontology 101: The California Pleistocene (Photo Diary)