What happened during this time?
The Period begins with carbon dioxide levels ~4,200 ppm, which jumps to 6,000 ppm in mid-Cambrian, and ending with 5,000 ppm
Oxygen levels are relatively stable during this time at 16.5%
Most of Cambrian life evolved and lived solely in the shallow seas that were formed as the supercontinent Pannotia split apart.
Probable bacterial/algal crusts were present on the landscape, especially in near water environments
Autotrophic bacteria flourishing in oceans
Stromatolites almost completely disappear
Algae dominant in oceans
There is no accepted evidence of life on land at this time
Possible terrestrial cyanobacteria, algae, and lichens
No evidence for plants on land; no soil available
Diversification of animal groups
Possible quick radiation of group called the "Cambrian Explosion"...
...although this pattern may be due to bias in sampling the fossil record (Servais et al. 2023)
Animals different in Ediacaran versus early Cambrian
Possible extinction event at the beginning of the Cambrian.
Evidence for this extinction event is also found in the carbon excursion used to date the beginning of the Cambrian.
Many earlier Ediacaran forms suddenly disappear at the beginning of Cambrian
The first coral reefs probably appeared in the Cambrian,
First confirmed hard-shelled animals appeared during the Cambrian, around 530 million years ago.
Trilobites were dominant during Cambrian
First vertebrates, such as Myllokunmingia, appeared
Soft-bodied fauna have been well-preserved in sediments of the Burgess Shale (505 Ma)
5 eyes, a backward-facing mouth underneath its head, and a proboscis extending forward from the head to end in a spined claw
Closely related to arthropods
Hallucigenia, which was supposed to have rows of rigid spines on which it walked, with tentacles waving at the top.
"Tentacles" then become legs for walking, and the rigid spines possibly a defensive mechanism