The La Brea website notes:

"Although the American mastodon was a relative of the prehistoric mammoths, there were considerable differences between the two animals. The two major differences were the animals' sizes and their teeth. The mastodons at Rancho La Brea were roughly half the size of the mammoths and stood about eight feet tall. Although the American mastodon had the same number of teeth throughout their normal lifetime as mammoths, they had more teeth in the jaw at any one time. The mastodon's simple and low crowned teeth indicate that this animal had the diet of a browser, an animal that tends to eat leaves and twigs. "

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