DISCLAIMER: This article is being kept online for historical purposes. Though accurate at last review, it is no longer being updated. The page may contain broken links or outdated information.
Earliest evidence of bilaterians
Pecoits, Ernesto Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada.
Konhauser, Kurt O. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada.
Aubet, Natalie R. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada.
Gingras, Murray K. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada.
- Geological setting and age
- Description and interpretation of the burrows
- Related Primary Literature
- Additional Reading
Life has existed on Earth for almost 4 billion years, but most major groups of animals only appear in the fossil record approximately 542 million years ago (MYA) in a relatively short period of time known as the Cambrian explosion of life. During much of the Precambrian, living organisms were small, unicellular, and comparably simple. In this context, the Ediacaran Period (630–542 MYA) is arguably one of the most critical periods in evolutionary history. Complex animals with bilateral symmetry (that is, with a front end and a back end, as well as an up side and a down side) probably emerged in the Ediacaran, but the timing of their appearance and diversification is still a matter of debate. A major factor that negatively affects our understanding of Ediacaran life is that the first animals lacked skeletons or any external hard parts; thus, they had a very low preservation potential. As such, fossilized tracks and trails (known as ichnofossils or trace fossils) provide important evidence of the first bilaterians.
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 46 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information