1. Timeline of Life on Earth

2. The Hadean: 4,600 – 4,000 million years ago
Pre-Cambrian
The Hadean: 4,600 – 4,000 million years ago
Not technically a geological era
No rocks from this time have survived

3. The Archean: 4,000 – 2,500 million years ago
Pre-Cambrian
The Archean: 4,000 – 2,500 million years ago
Era begins with the oldest rocks (4 bya)
First life appears in the fossil record at 3.8 bya
Life was purely bacterial for million years
Bacterial lived in mounded colonies called stromolites
living stromatolites persist today in western Australia

4. The Proterozoic: 2,500 – 542 million years ago
Pre-Cambrian
The Proterozoic: 2,500 – 542 million years ago
Stromolite presence in the fossil record grows, along with species diversity
First pollution crisis in the fossil record at 2.2 bya. Rocks start showing metal oxides -> points to oxiiication of atmosphere
Cyanobacteria responsible for “poisoning” the air, stromatolite abundance declines at 700 mya
Eucaryotes first appear in the fossil record at 1800 mya
First animals appear in fossil records at 635 mya
cyanobacteria

5. Where we are now..

6. The Cambrian: 542 – 485.4 million years ago
Phanerozoic: Paleozoic
The Cambrian: 542 – million years ago
Explosion of extant phyla, except Bryozoa
While the phyla are extant, Cambrian animals belong to classes not found in the present
brachiopods were exceptionally common and diverse
everything still living in the seas
brachiopod

7. The Ordovician: 485.4 – 443.8 million years ago
Phanerozoic: Paleozoic
The Ordovician: – million years ago
Begins with the Cambrian–Ordovician extinction event: extinction of brachiopods and trilobites (not considered a mass extinction)
Ordovician is known for establishing ecological diversity in the seas: reef- forming corals, filter feeders, etc.
Mollusks diversified, first jawed fish appears in fossil record
nautiloids

8. The Silurian: 443.8 – 419.2 million years ago
Phanerozoic: Paleozoic
The Silurian: – million years ago
Begins with the first mass extinction: Ordovician–Silurian mass extinction
Second-largest mass extinction (actually two pulses): 60% of the marine invertebrate fauna went extinct
Major diversification of jawed and boney fish
first land vascular plants (mosses), but not very important
Also very first land animal: a millipede (428 mya)
Silurian fish

9. The Devonian: 419.2 – 358.9 million years ago
Phanerozoic: Paleozoic
The Devonian: – million years ago
Begins with adaptive radiation of terrestrial life
Free-sporing plants colonized dry land, leaving massive forests
Terrestrial arthropods diversified: only possible because of dominance and diversification of land plants
Age of fish: first ray-finned fish appear (Actinopterygii, 99% of extant fish species belong to this class)
Ends with the second mass extinction: actually two events. Several competing theories.
Devonian

10. The Carboniferous: 358.9 – 298.9 million years ago
Phanerozoic: Paleozoic
The Carboniferous: – million years ago
Massive forests (ferns, horse-tails, and other non- flowering plants)
Coal deposits formed because of un-decomposed woody material (first trees) in massive swamps, (and probably because bacteria and fungi hadn’t yet evolved to efficient enzymes for decomposition).
Age of the terrestrial amphibian. Some 6 meters long!
Amniotic egg develops (allows for radiation of terrestrial tetrapods: turtles, reptiles, birds, mammals)
Carboniferous forests
turtle egg

11. The Permian: 298.9 – 252.17 million years ago
Phanerozoic: Paleozoic
The Permian: – million years ago
Begins with the Carboniferous rainforest collapse, where swampy forest gave way to arid deserts
Pangea is formed
At beginning of Permian, 90% of insects were cockroach- like Blattoptera. Giant dragonflies evolve.
Late Permian: many other species rich insect orders are formed: Hymenoptera (bees, wasps), Coleoptera (beetles), Lepidoptera (butterflies), Diptera (flies). Most significant time for insect radiation.
Drier conditions favored amniotes: first fossils of mammals, turtles, lepidosaurs (modern reptiles), and archosaurs (dinosaurs, crocodiles, birds).
Permian

12. The Permian – Triassic mass extinction: 252.17 million years ago
80% of marine genera go extinct
Estimated that 96% of marine species, 86% of insect genera, and 70% of terrestrial vertebrates went extinct
Took between 10 and 30 million years for biodiversity to recover
Causes unclear: bolide impact, volcanism, methane gasification (maybe because of sea level drop or new enzymatic pathway in microbes, sudden increase in CO2 causing ocean die off and cascade…
massive ecological rearrangement favors pioneer taxa, in plants, particularly lycophytes (club mosses)

13. Where we are now..

14. The Triassic: 252.17 – 201.3 million years ago
Phanerozoic: Mesozoic
Low diversity persists for long time during Triassic
Dominant marine habitats shifts from sessile to benthic
Pangea begins to split into Laurasia and Gondwana in mid-Triassic
Land plants dominated by confiers, cycads, ginkgos, and ferns
It takes a long time for dinosaurs to become dominant: late Triassic opens the “Age of Dinosaurs”
Lystrosaurus: most dominant land vertebrate of early Triassic

15. The Jurassic: 201.3 – 145 million years ago
Phanerozoic: Mesozoic
Once again, begins with a mass extinction event: the Triassic–Jurassic extinction event:
1 of 2 species goes extinct in just 10,000 years! On land, ecological niches open to allow dinosaurs to dominate. (Volcanoes are best guess as to cause)
There were still no flowering plants – all trees were conifers!
Sauropods: large, herbaceous dinosaurs dominate

16. The Cretaceous : 145 – 65 million years ago
Phanerozoic: Mesozoic
Flowering plants appear (but not dominant)
Mammals and birds also are more apparent (technically, both groups first appear in Jurassic)
Era of the best known dinosaurs: T. rex, Triceratops, Velociraptor, etc.
Abruptly ends with the K-T mass extinction.
75% of plant and animal species go extinct, including all non-avian dinosaurs
Triggered by massive comet/asteroid impact in Yucatán
Reconstruction of type specimen (CM 9380) of Tyrannosaurus rex (Carnegie Museum of Natural History)

17. The Paleocene : 66 – 38 million years ago
Phanerozoic: Cenozoic
Nearly every bird order radiated during first 10 million years. Mammals radiate afterwards
Starts hot and humid, ends cooler and drier. Tropical forests found in Alaska.
Fifth mass extinction occurs during this period: mostly marine, maybe not really a mass extinction

18. The Neogene : 38 – 2.58 million years ago
Phanerozoic: Cenozoic
Seasonality dominates climate (before, climate wasn’t very seasonal!)
Global climate continues to cool.
Deciduous forests and grasslands replace tropical forests
Isthmus of Panama forms at 3 mya, creating the jet stream

19. The Quaternary : 2.58 million years ago to present
Phanerozoic: Cenozoic
Ice Ages!
It is generally believed that Quaternary climate patterns shape the current distribution of most terrestrial plants and animals.
A genus of stone-tool using apes first appears in the fossil record