Lecture - 17 - Week 10 - Cambrian Explosion Flashcards
What are some important Cambrian groups?
Chordates, arthropods, mollusca, brachiopoda, cnidaria, echinodermata, annelida
First fossil evidence of multicellular animals is from the…
Ediacaran Period: 635 - 541 MYA
How were the Ediacaran biota preserved?
Via molds and casts since they didn’t have skeletons.
Some of the Ediacaran fossils resemble modern animal groups; however…
First trace fossils around 560 MYA are a result of…
Bioturbation (movement of soils and sediments by digging, walking, burrows, trackways, etc. of animals)
When did the first skeletonized animal fossils occur…
C. 550 MYA
What did they look like?
Unusual, and most lacked skeletons.
Was the rise of animals rapid (geologically speaking)?
Yes, with the introduction of major animal groups.
What is the Phanerozoic Eon? Dates?
The period when animals became visible and complex. 538 MYA to present.
Why do we know so much about the Phanerozoic Eon?
Less time for rocks to be destroyed, and a more complete fossil record due to increase in diversity and size.
Animals also mineralize and have more shells, skeletons, teeth, jaws, etc.
4 key events and concepts of the Cambrian period…
- Large animals evolve
and radiate (i.e.,
“Cambrian Explosion”) - Evolution of “hard
parts” - Cambrian substrate
revolution (fossils of bioturbation) - Trilobites dominate;
form basis for
stratigraphic
subdivision of
Cambrian
What happened with animals in the Cambrian period?
They evolved mineralized skeletons, shells, etc. They grew larger.
What differentiates Early Cambrian fossils?
“Small, shelly fossils” with intense diversity “experimentation” of forms.
What animal is popularly associated with the Cambrian
The trilobite. They experienced intense diversification.
What can trilobite biozones be used for?
To form the basis for stratigraphic subdivision of the Cambrian period.
