What are acritarchs?
Q: What are acritarchs?
A: Acritarchs are early microfossils, the remains of eukaryote cells. They have a single-layered cell wall or a cover secreted by the cell walls that can be found in rocks from the Proterozoic era.
Q: What is their chemical composition?
A: Acritarchs are organic in their chemical composition, not calcium carbonate.
Q: When did they first appear?
A: Acritarchs first appeared 1.4 to 1.6 billion years ago in organic-rich shales and siltstone strata.
Q: Are they monophyletic?
A: It is not clear whether or not acritarchs are monophyletic due to the wide range of forms they take on.
Q: Why did their populations crash during the Cryogenian period?
A: The populations of acritarchs crashed during the Cryogenian period 860 million years ago due to Snowball Earth episodes.
Q: Why did they become more spinney over time?
A: The increased spininess of acritarchs possibly resulted from the need for defence against predators large enough to swallow them or tear them apart.
Q: Did other groups of organisms also develop anti-predator defences at this time?
A: Yes, other groups of small organisms from the Neoproterozoic era also show signs of anti-predator defences.
