Cenozoic

Question 1

What is the K-T Extinction?

Answer 1

The best studied mass extinction (now called K-P for Paleogene), marking the extinction of ammonites, non-bird dinosaurs, marine reptiles, and flying reptiles among other groups.

Question 2

What the iridium evidence for the KT Extinction?

Answer 2

The main evidence for an extraterrestrial impact is the presence of an Iridium Anomaly at this age in sediments around the world. The amounts of iridium found in rocks at the KT boundary are between 20-160x higher than the amount in typical crustal rocks. Iridium is rare in the earth’s crust, but it is common in meteorites in the earth’s mantle. It is believed that the extinction is caused by a meteor or asteroid about 10-20 km in diameter (by how much iridium is found), it is believed to have landed in the Yucatan Peninsula.

Question 3

What is the crater where the KT meteorite hit?

Answer 3

In the Chicxulub Crater in the Yucatan Peninsula. There are gravity anomalies.

Question 4

What is the quartz evidence for KT extinction?

Answer 4

The other main piece of evidence for an extraterrestrial impact is the presence of shocked quartz (microscopic breaks), caused when quartz is placed under immense pressure. Found all over North America.

Question 5

What is the microspherules evidence for KT extinction?

Answer 5

Evidence for the impact; when the meteorite hit the earth a lot of dust-sized debris rose, and the bigger pieces hit the earth again and were mini-meteorites. The medium chunks melted as they fell down towards the earth and froze in the last bit of the fall and so they froze in balls of glass. Thought to be evidence or meteorite impact - problem is that they are usually spherical structures from different periods/or contamination of insect eggs.

Question 6

When was the Cenozoic?

Answer 6

Periods of Paleogene, Neogene (65 MYA - 0 MYA).

Question 7

What is the world like in the middle eocene?

Answer 7

North America, South America, and Africa are now in familiar shapes. Asia is still weird, Europe is a chain of small islands (no Alps). NA and SA are not connected to each other (no central America).

Question 8

What is the world like in the middle Miocene?

Answer 8

India has collided with Asia (Tibetan Plateau); Europe is weird still. NA and SA have almost met each other but there is still gaps. Glaciers have formed in Greenland, Hudson’s Bay is still dry land.

Question 9

What is the world like 18,000 years ago?

Answer 9

The Last Glacial Maximum - large glaciers; NA and Europe and Asia are covered in massive ice sheets. Kilometres thick. Areas near the Yukon/Alaska border were not covered.
Australia was almost connected to Asia. Water level was so low that the Mediterranean Sea wasn’t connected to anything and almost dried up several times.

Question 10

How long did it take for the dominant land vertebrates of the Late Cretaceous to be replaced after the KT extinction?

Answer 10

5-10 million years.

Question 11

What happened before the land vertebrates were replaced?

Answer 11

During that time there were no large herbivores and there were very few predators of any size. The ones around are lizards, crocodiles, birds - things that survived the KT Extinction.

Question 12

What was present around the end of the Paleocene?

Answer 12

There are several 4-5 tonne herbivorous mammals, which are of different ancestry on separate continents; there are large carnivorous birds (Terra birds) that were the main predators.

Question 13

What happened to marine reptiles after the KT extinction?

Answer 13

No marine reptiles survived, and it wasn’t until the Eocene that animals came to fulfill those roles (whale eating fish).

Question 14

What was the environment like during the Paleocene and Eocene?

Answer 14

The mean annual temperatures were high, and abundant precipitation fell, and tropical to semitropical forests covered much of North America.

Question 15

Mammalian Orders by the Eocene.

Answer 15

Many mammalian orders that evolved during the Paleocene become extinct but of the several that first appeared during the Eocene only one has become extinct; by the Eocene time many of the mammalian orders existing now were present (e.g. ancestors of horses, camels, elephants, rhinos, whales, bats). Yet if we could go back for a visit we would not recognize most of these animals.

Question 16

What life existed in the Eocene?

Answer 16

Large herbivores that are not extinct. By the Eocene, mammals included many giant yet small-brained rhino-like types. Not closely related to living herbivores today. The Asiamerican uintatheres and brontotheres.

Question 17

The Invasion of Air: Bats.

Answer 17

The oldest fossil bat (order Chiroptera) comes from the Eocene-age Green River Formation of Wyoming, but well-preserved specimens are known from several other areas, too. Apart from having forelimbs modified into wings, bats differ little from their immediate ancestors among the insectivores. These bats could not locate food by echolocation.

Question 18

Miocene and Pliocene animals.

Answer 18

By the Miocene and Pliocene time most of the mammals were quite similar to those existing now. On close inspection, though, horses have three toes, cats have huge canine teeth, deer-like animals with forked horns on their snouts, very tall/slender camels. A few odd mammals, but the overall fauna is quite familiar.

Question 19

The Ungulates or Hoofed Mammals.

Answer 19

The term ungulate is an informal one referring to several groups of living and extinct mammals. It refers to having hoofs, but not all ungulates have hoofs-however, the most numerous ungulates are indeed hoofed mammals belonging to the orders Artiodactyla and Perissodactyla.

Question 20

What are the Artiodactyla?

Answer 20

Commonly called even-toed hoofed animals, are the most diverse and numerous (living today) with about 170 living species of cattle, goats, sheep, swine, antelope, deer, giraffes, hippos, camels, and several others.

Question 21

What are the Perissodactyls?

Answer 21

Odd-toed hoofed mammals, only 16 exiting species of horses, rhinos, and tapirs. Mostly extinct (many zebras, but not many wild horses).

Question 22

How have hoofed mammals changed over time?

Answer 22

Perissodactyls have one or three functional toes and carry the weight on the third toe whereas artiodactyls have two or four toes and they walk on toes 2 and 4.
In both of these groups they have, overtime, become adapted for running quickly through longer legs (longer steps) and quicker strides (lighter, thin legs), typically it is the bottom of the leg that lengthens (below the ankle becomes very long).

Question 23

Horse Evolution.

Answer 23

Some evolutionary trends include an increase in size, lengthening of the limbs, reduction in number of toes, and development of huge high-crowned teeth with complex chewing surfaces.

Question 24

What are the largest land mammals in earth history?

Answer 24

Baluchitherium (Oligocene Gigantism). A hornless rhino (6 m at its shoulder).

Question 25

Whale Evolution.

Answer 25

Whales evolved from Artiodactyla (the mammalian order including cows, deer, hippos, etc.), evidence for this comes from genetics and ankle structures in the fossil bones.

Question 26

Grass Evolution.

Answer 26

During the Miocene grasses spread widely for the first time grassy plains and prairies appear for the first time. This forced mammals to adapt to the changing environment.

Question 27

What was the Late Pliocene Interchange?

Answer 27

Through most of the Cenozoic, South America was an isolated island with its own fauna. In the Late Pliocene the Isthmus of Panama formed, allowing animas to migrate between North and South America. Possums came from South America.

Question 28

What were the Ice Ages of the Pleistocene?

Answer 28

The Pleistocene was a time of major continental glaciation. During this period, up to 1/3 of the earth’s land was covered in ice and snow. This greatly effected the climate of the entire earth, not just the regions covered by the glaciers. Climatic zones in the Northern Hemisphere shifted southward. Canada was almost completely covered in a Continental Glacier.