Earth Sciences 2266F/G Lecture Notes - Lecture 29: Uintatherium, Isthmus Of Panama, Gulf Stream

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Lec 29
Placental Mammal Explosion: all ancestors just came out at the same time more or less
Not too long after their appearance, gigantism started led by herbivores (e.g. Uintatherium:
rhino-sized herbivore)
Most mammal evolution occurred on land and remained on land (not whales, etc.); there is co-
evolution between expansion of grassland and learning how to eat grass in herbivores
But also have to grow bigger and run faster in order not to be eaten in the barren grassland with
no cover
Carnivores: in dinosaurs, predators like T. Rex was much bigger than the prey
But not for mammals; in terms of mammal size, mammal predators are always smaller than the
herbivores (e.g. lion and elephant)
Carnivores found a way to take down herbivores
Any time there is a major change, the beginning of the evolutionary pathway appears very
quickly (in terms of mode of life), and then as it evolves species are just fine-tuning those
evolutionary features
Uintatherium seen here
- Quite big; beginning of gigantism
Within hoofed animals, there is divergence between herbs and carnivores
Today, all hoofed are herbivores
In the beginning, there were both
Carnivore group evolved into whales
- Creodonts not directly related to carnivora, and became extinct
By Oligocene, mammals got even bigger like the rhino; early pig ancestors appeared (as much as
5x bigger than today’s pigs)
Also camel-like creatures
- Hyaenodon was a hoofed predator
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