Chapter 16: Cenozoic Life

ere there general names for specific periods and/or eras (e.g., Age of Dinosaurs)?

Yes. The Cenozoic is often called the 'Age of Mammals' because mammals diversified rapidly after the K–Pg extinction, filling ecological niches once occupied by dinosaurs.

What were the large animals in the sea? On land?

Sea: Whales (including blue whale, largest animal ever), giant sharks like Megalodon, large teleost fishes, seals, sea lions. Land: Indricotherium (largest land mammal ever), proboscideans (elephants, mammoths, mastodons), horses, large cats, giant ground sloths, bison, camels.

What was GABI? What was the Bering Land Bridge?

GABI = Great American Biotic Interchange, Neogene event where closure of the Isthmus of Panama allowed mixing of North and South American faunas. Bering Land Bridge = land connection between Asia and North America during Quaternary glacial low sea levels, enabling migrations of humans and animals.

What were the effects of glaciation?

Glaciations covered ~1/3 of Earth's land with ice; lowered sea levels by ~120 m; exposed land bridges; formed moraines, erratics, pluvial lakes; caused isostatic rebound; shifted climate zones and ecosystems.

What is Tule Springs?

A fossil site near Las Vegas preserving late Pleistocene Ice Age wetlands and megafauna like mammoths, camels, lions, saber-toothed cats. Important for understanding Ice Age ecosystems in the Great Basin.

What is La Brea Tar Pits?

A fossil site in Los Angeles where natural asphalt trapped and preserved Ice Age megafauna such as dire wolves, saber-toothed cats, and mammoths. Exceptional preservation of bones.

Adaptive Radiation

Rapid diversification of species to fill ecological niches, often after extinctions (e.g., mammals after K–Pg, Paleogene).

Age of Mammals

Nickname for the Cenozoic Era when mammals became dominant on land and in the sea.

Bering Land Bridge

Land connection between Asia and North America during glacial sea-level lows, mainly Quaternary.

Erratics

Large boulders transported by glaciers and deposited far from their origin.

GABI

Great American Biotic Interchange, Neogene event after Isthmus of Panama closure, mixing N and S American fauna.

Grasslands

Open biomes that expanded in Oligocene–Miocene; drove evolution of grazing mammals like horses.

Horses

Evolved in North America, adapted from small browsers to large grazers with high-crowned teeth in Neogene grasslands.

Indricotherium

Largest land mammal (hornless rhino relative), lived in Paleogene–early Neogene, giant browser.

Isostasy

Crustal balance—land sinks under ice sheets and rebounds after melting.

La Brea Tar Pits

Los Angeles asphalt seeps preserving Pleistocene Ice Age animals.

Laurentide Glacier

Massive Pleistocene ice sheet covering much of North America.

Megalodon

Giant Neogene shark, apex predator preying on whales.

Moraines

Ridges of debris deposited at glacier margins.

Neogene

Cenozoic period after Paleogene; includes GABI, megalodon, grassland expansion, Basin and Range extension.

Paleogene

Early Cenozoic period; mammal adaptive radiation; early whales; PETM warming event.

Pluvial lakes

Large inland lakes formed in cooler/wetter glacial climates (e.g., Bonneville, Lahontan).

Primates

Mammal order (monkeys, apes, humans) evolving by early Cenozoic; adapted to open habitats later.

Proboscideans

Elephants and extinct relatives (mammoths, mastodons) abundant in Cenozoic.

Quaternary

Most recent Cenozoic period (Pleistocene + Holocene); glaciations, humans, megafaunal extinctions.

Sharks

Diversified in Cenozoic, including apex predators like megalodon and modern great whites.

Teleost

Advanced ray-finned fishes; diversified after K–Pg and dominate modern seas.

Tule Springs

Nevada Ice Age fossil site with Pleistocene wetlands and megafauna.

Whales

Marine mammals evolving in Paleogene; blue whale largest ever.

During which period did mammal adaptive radiation begin?

Paleogene.

During which period did Indricotherium live?

Paleogene–early Neogene.

During which period did megalodon dominate as apex predator?

Neogene.

During which period did GABI occur?

Neogene (Miocene–Pliocene).

During which period was the Bering Land Bridge most significant for human migration?

Quaternary (Pleistocene).

During which period were the La Brea Tar Pits fossils deposited?

Quaternary (Pleistocene).

During which period was Tule Springs active as a wetland habitat?

Quaternary (late Pleistocene).

During which period did major Northern Hemisphere glaciations occur?

Quaternary (Pleistocene).

During which period did whales evolve into fully marine forms?

Paleogene.

During which period did grasslands expand significantly?

Neogene.

Which two continents were connected during GABI?

North America and South America.

What geological change allowed GABI to occur?

Closure of the Isthmus of Panama.

What plant group’s spread drove evolution of high-crowned teeth in grazers?

Grasses.

What is isostatic rebound?

The rise of land after the weight of glacial ice is removed.

Name two features created by glaciers.

Moraines and erratics (also drumlins, eskers, till).

What caused sea levels to drop during glaciations?

Water storage in ice sheets.

Name two Pleistocene pluvial lakes in the Great Basin.

Lake Lahontan and Lake Bonneville.

Which Cenozoic marine vertebrates replaced mosasaurs as apex predators?

Sharks and whales.

What is the largest animal to have ever lived?

The blue whale (Paleogene to present).

What era preceded the Cenozoic?

The Mesozoic Era.

What animal were small statured animals fitted to a life of browsing between trees?

Ancestors of horses

What epoch did the Great American Biotic Interchange occur?

Pliocene (Neogene).

What connects North and South America?

The Isthmus of Panama.

What was the name of the shark that could grow up to 60 feet long in the Neogene?

Megalodon.

Which mammal order includes elephants, mammoths, and mastodons?

Proboscideans.

What was the largest land mammal to ever live?

Indricotherium (Paraceratherium).

What are the large boulders carried by glaciers called?

Erratics.

What is the process where Earth's crust rebounds after ice melts?

Isostatic rebound.

What period did the first true primates appear?

Paleogene.

Which large Ice Age lake was in the area of present-day Utah?

Lake Bonneville.

Which large Ice Age lake was in the area of present-day Nevada?

Lake Lahontan.

What was the largest Ice Age glacier in North America?

Laurentide Glacier.

What caused sea level to drop during glaciations?

Water stored in continental ice sheets.

What is the common name for the Cenozoic Era?

Age of Mammals.

What was the largest animal to ever live?

Blue whale.

Where is the La Brea Tar Pits located?

Los Angeles, California.

Where is Tule Springs located?

Near Las Vegas, Nevada.