What are small shelly fossils?
Q: What are small shelly fossils?
A: Small shelly fossils (SSF) are tiny fossils, many only a few millimetres long. They have a record from the latest stages of the Ediacaran to the early Cambrian period.
Q: How were most SSFs preserved?
A: Most SSFs were preserved by being covered quickly with phosphate. This method of preservation is mainly limited to the later Ediacaran and early Cambrian periods.
Q: What do some of the fossils represent?
A: Some of the fossils represent the entire skeletons of small organisms, including mysterious Cloudina and some snail-like molluscs. However, most are fragments or parts of larger organisms such as sponges, molluscs, slug-like halkieriids, brachiopods, echinoderms, and onychophoran-like organisms that may have been close to arthropod ancestors.
Q: What was one explanation for why SSFs appeared?
A: One explanation for why SSFs appeared was a sudden increase in ocean's concentration of calcium which allowed animals to form mineralized skeletons. However, many SSFs are made out of other minerals such as silica so this explanation is not definitive.
Q: When did these first appear?
A: The first SSFs appear around same time as organisms started burrowing to avoid predation so it is likely they represent early steps in an evolutionary arms race between predators and increasingly well-defended prey.
Q: Why are they difficult to identify and classify?
A: The small size and (usually) broken nature of SSFs makes them difficult to identify and classify accurately.
Q: What advantages do they provide evidence for?
A; They provide evidence for how main groups marine invertebrates evolved, pace and pattern evolution during Cambrian explosion, earliest known representatives modern phyla whose bodies include hard parts
