THIRTY-SIX

Emergent Silurian Period: 443 - 419 mya

Features of the Silurian period: 443-419 mya:

1) There is a "...rapid recovery in biodiversity after the end-Ordovician extinction event..." (The Geologic Time Scale, 2012, p. 525).

5) Jawed and bony fishes, air-breathing animals (arthropods such as millipedes, centipedes, crabs, and spider-like organisms), and terrestrial plants colonize the seas and Earth, the plants providing the first terrestrial animals with shelter and food.

6) Eurypterids (sea scorpions), i.e. arthropods (hard exoskeleton or cuticle for protection and moisture retention, jointed legs) become a dominant marine predator. 

7) Vascular plants evolve, with internal circulation of water and nutrients.

2) The South Pole migrates over South American and South African Gondwana (ibid., p. 525).

4) Supercontinent Gondwana fills the southern hemisphere, while N. America is covered by shallow seas.

3) Conversion of continental plates, and land colonization (by flora? by fauna?) occurs (ibid., p. 525).