FORTY-ONE

Emergent Jurassic Period: 201 - 145 mya

Features of the Jurassic period: 201 - 145 mya:

1) Named after the Jura Mountains between France and Switzerland, this is the middle period of the Mesozoic era.

2) The North Sea oil fields were deposited during this period.

3) At the beginning of this period, the supercontinent Pangaea begins to break up, into northern Laurasia, and southern Gondwanaland, with rift valleys marking the vast and powerful forces of continental separation.

4) The earliest of mammals appeared (e.g., hadrocodium, 195 mya, with fur, and 3 floating ear bones).

5) Reptiles dominated the land, marine, and air animals:

                  a) dinosaurs dominated the land;

                  b) crocodiles, ichthyosaurs, and plesiosaurs dominated the sea; and

                  c) pterosaurs inhabited the air.

6) Archaeopteryx lithographic (155 mya) is the earliest known bird, or considered a transitional form between reptiles and birds. Theropod dinosaurs (with hollowed bones) evolved feathers for warmth, and birds subsequently used feathers for flight.

7) Toothed birds evolve, and become extinct during the next (Cretaceous) period.

8) Dinosaurs comprised 2 main groups, based on the structure of their pelvis:

a) saurischians - included the gigantic carnivores: Tyranosaurus, Gigantosaurus, and Carcharodontosaurus; some were quadrupedal herbivores, 100 feet long weighing 100 tons.

b) ornithischians - backward-extended pubic bone; strictly herbivores; mostly quadrupedal; some with bird-like beaks; some with armor plates.