1. Fossils
Lecture 1

2. Geologic Time Scale
From largest to smallest: Eon, Era, Period, Epoch, Age
There is also an even larger section called a supereon. However, we do not care about this one as there is only one: the Precambrian
We will also not be too concerned with memorizing epochs and ages
There are 4 eons (from oldest to most recent): the Hadean, the Archean, the Proterozoic and the Phanerozoic
The Hadean, Archean and Proterozoic are part of the Precambrian, we won’t worry about these too much for now.

3. Precambrian ( mya)
Very little is known about this supereon because lifeforms in this time lacked hard shells or skeletons
We have found fossils that we call stromatolites that show indications of the presence of cyanobacteria. These were first found in the Archaean Eon.
The first evidence of life probably first emerged mid-Hadean

4. Phanerozoic (540 mya-present)
Shelled invertebrates first begin to emerge during the Phanerozoic Eon, as such we have a much better understanding of lifeforms during this time
This Eon is divided into 3 Eras (oldest to most recent): Paleozoic, Mesozoic, Cenozoic
Each era was dominated by different types of animals

5. Paleozoic ( mya)
Name refers to “ancient animals” as the age was dominated by marine invertebrates
Divided into 6 periods
Cambrian and Ordovician Periods – marine invertebrates emerge along with primitive fish. These two periods form the “age of invertebrates”
MASS EXTINCTION EVENT
Silurian and Devonian – Early land animals and amphibians emerge as well as forests. These periods form the “age of fishes”
Carboniferous – Further divided into Mississippian and Pennsylvanian periods. Shallow seas and coal bearing rocks form in the two periods respectively
Permian – Earliest gymnosperms or cone-bearing trees begin to form. Together with the Carboniferous period forms the “age of amphibians”

6. Mesozoic (251.1-65.5 mya) Dinosaurs!!!
More boringly “the Age of Reptiles”
Triassic Period – First dinosaurs and the earliest mammals emerge
MASS EXTINCTION EVENT
Jurassic Period – Earliest birds
Cretaceous Period – Flowering plants develop. This is where all the cool looking dinosaurs emerge.

7. Cenozoic (65.5mya-present)
Divided into 2 Periods: Tertiary and Quaternary
The Tertiary period is further divided into the Paleogene and Neogene periods (as seen on your sheet)
The Cenozoic differs from previous eras because the periods can further be divided into Epochs

8. Tertiary ( mya)
Divided into 5 epochs that we won’t be going into specifically
Apes, birds and grazing animals develop. Like REALLY big birds.
The first modern animals develop near the end of this period.

9. Quaternary (1.8mya to present)
This is where humans first emerge
Divided into epochs that we also don’t really care about differentiating
We are in the:
Phanerozoic Eon
Cenozoic Era
Quaternary Period
Holocene Epoch