Cretaceous
GEOGRAPHY AND CLIMATE: Seas flood half the land, Great thickness of
chalk, single-celled animals laid down. Land masses
begin to move towards their present positions. Climate mild without
extremes.
TERRESTRIAL ANIMAL LIFE: Advanced dinosaurs such as duck-bills. Turtles,
snakes,salamanders. Gulls and wading birds. Opossums & other mammals.
All dinosaurs and many other large reptiles extinct by the end of
the period.
PLANT LIFE: Gymnosperms, sequoias and cypresses. Flowering plants appear,
magnolias and oaks.
SEA LIFE: Plankton, coral reefs, rudists, ammonites, calcareous algae.
Marine reptiles and ammonites extinct by the end of the period.
Jurassic
GEOGRAPHY AND CLIMATE: Gondwanaland continues to break up, Graywacke,
shale and siliceous sediments formed. Continued mountain building.
mild, moist climates over most of the land.
TERRESTRIAL ANIMAL LIFE: Reptiles dominant with Crocodiles, turtles,
lizards and dinosaurs. Pterosaurs and Archaeopteryx take to the air.
Mammals begin to diversify. More advanced insects such as flies.
PLANT LIFE: Cycads, ginkos, conifers, ferns and tree ferns.
SEA LIFE: All major invertebrate groups well represented, ammonites and bivalves successful. Marine reptiles, Ichthyosaurs are Plesiosaurs.
Triassic
GEOGRAPHY AND CLIMATE: Sea levels very low. Graywacke shale, siliceous and Red desert sandstone deposits, arid climate over most of land Pangaea begins to split. Atlantic Ocean opens up.
TERRESTRIAL ANIMAL LIFE: Reptiles dominant, including the ancestors of the dinosaurs and mammals.
PLANT LIFE: Gymnosperms such as ferns, cycads, gingko's and conifers.
SEA LIFE: Ammonites dominate the seas, Bivalves and Brachiopods are locally abundant but generally rare. All other major invertebrate groups are rare of missing.
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