Phanerozoic Life Moves to Land
Phanerozoic Objectives
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Provide the approximate time span, geologic changes, and representative organisms of the Phanerozoic Eon, including the Paleozoic, Mesozoic, and Cenozoic Eras.
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Tell the dinosaur story including evolutionary origins, structural features, major taxonomic groups, new avenues of research, and theories for their extinction.
The Precambrian Supereon ended with a variety of oceanic organisms: bacteria, complex single-celled eukaryotes, and multicellular organisms including the first animals.
That leaves a lot of life to come in the Phanerozoic Eon, including the move to land and origin of the vertebrates.
This video introduces the Phanerozoic Eon.
This video introduces Brachiopods and the sources of data for the figure below.
Assuming that the specimens recorded in fossil sheet #1 are older (deeper in the rock strata) than those from fossil sheet #2, hypothesize how the variation in the widths of the Brachiopods of fossil sheet #1 led to the widths observed in fossil sheet #2.
Dinosaurs
Dinosaurs and other large reptiles ruled the Earth’s ecosystems during a portion of the Phanerozoic Eon. This is their triumphant and then tragic story.
In the past few decades, new dinosaur fossil finds have made this group of reptiles even more interesting.
We’ll begin with a general look at the major groups of dinosaurs.
Ornithischians
“Bird-like” pelvis, these herbivores include stegosaurus, hadrosaurs, and triceratops.
Sauropod Saurischians
Herbivorous dinosaurs with a lizard-shaped pelvis. Many were massive, including Brachiosaurus.
Theropod Saurischians
Carnivorous dinosaurs with a lizard-like pelvis, including T. rex and velociraptors. This lineage gave rise to modern birds.
Stegosaurus, an ornithischian herbivore, is one of the best-known dinosaurs. The spiked tail may have been a defense against predators, and the raised plates may have been used for display or possibly cooling.
Evolutionary trees are used to organize different types of dinosaurs.
Brachiosaurus is one of the iconic sauropods, recognizable with its upright stance.
These videos were made at Prehistoric Gardens on the Oregon Coast. A lot of care has gone into the construction of these statues and it is worth a stop while driving highway 101.
Start Your Guide 7A Media Assignment here
Geologic Timeline
Based on the information on this Phanerozoic Eon webpage and the previous Precambrian Supereon page, construct a timeline that shows the relative lengths of geologic time and representative organisms. This can be paper, digital, or other materials.
Include:
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The order and relative lengths of the Precambrian Supereon and its three Eons (Hadean, Archaen, Proterozoic) and the Phanaerozoic Eon and its three Eras (Paleozoic, Mesozoic, and Cenozoic.
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Indications of the approximate time (Eon or Era) when these organisms appear in the fossil record: earliest bacteria, cyanobacteria, eukaryotes (complex single cells), multicellular organisms, the first animals, fish, land plants, reptiles/amphibians, mammals/birds.
The Precambrian will be very long relative to the Phanerozoic Eon; you may need to have a creative way of looping the timeline. The eras are also different relative lengths.
This can be challenging, but an effective way to learn the order of geologic time. The time spans can be found through Wikipedia and other online sources. Be aware, they often don’t show the relative lengths, many illustrations shorten the Precambrian for convenience.
Knowledge about dinosaurs continues to change. The next section explores how scientific knowledge can be both tentative and durable.
Check your knowledge. Can you:
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provide the approximate time span, geologic changes, and representative organisms of the Phanerozoic Eon, including the Paleozoic, Mesozoic, and Cenozoic Eras?
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tell the dinosaur story including evolutionary origins, structural features, major taxonomic groups, new avenues of research, and theories for their extinction?
Go back to the Precambrian Page
Go forward to the Tentative & Durable Page
Geologic Time Guide Contents
Complete all four of these sections before taking the quiz and making your media piece.
Back to Evolution
Module 7
This Guide
7A: Geologic Time
Products Information
7A: Quiz & Media
