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Period the largest had a wing span of only 1 metre. Archaeopteryx, the first true feathered bird, but still with reptile-like teeth, also evolved during the Jurassic Period.
The Cretaceous Period
65 million to 135 million years ago
Ammonoids, belemnites, flying reptiles, dinosaurs, marine reptiles all become extinct at end of period. Scleractinian corals (hexacorals) develop, gastropods, molluscs, ammonites, belemnites, sponges, dinosaurs are common. First recorded primates, modern fish
The Cretaceous Period was a long, fairly recent period, when extensive shallow seas produced enormous sheets of rock. Cretaceous rocks are more common than rocks from any other period.
Algae flourished in this time, forming the chalk rocks that are one of the dominant forms of Cretaceous limestone.
All marine life flourished in these seas, and many groups were more abundant at this time than at
any other time in their history. Corals, for example, were extremely varied and more important reef builders than today. A group of molluscs, called rudists, were also so prolific that they built huge reefs by cementing their cone-shaped valves together. Ammonoids continued to thrive and are used as index fossils just as they were in the Jurassic Period. Gastropods became more numerous. Echinoids continued to thrive. The modern fishes evolved to dominate the seas.
Of the marine reptiles, the plesiosaurs were replaced by lizard-like mosasaurs which had flippers rather than legs. They reached 17 metres in length. During the Cretaceous Period the pterosaurs became giants, with wing spans of nearly 8 metres. The Cretaceous Period, however, is known for the evolution of Tyrannosaurus, the world’s largest ever land predator, reaching 14 metres in length and standing over 6 metres high.
(Above) Cretaceous: sponge (Raphidonema faringdonensis).
(Above) Cretaceous: ammonite.
(Above) Cretaceous echinoid: Micraster.