Mesozoic

TRIASSIC (250-210 million years ago)
Among plants highly developed gymnosperms dominanated. The primitive amphibians became extinct. Reptiles diversified. Small, primitive dinosaurs appeared. They were mainly carnivorous. Morphologically they only foreshadowed the giant forms which were to follow in Jurassic period. The flying reptiles pterosaurs made their debut. First egg-laying mammals appeared. These mammals were reptile-like in many aspects. They are sometimes referred to as the proto-mammal. The descendants of them survive today in the duckbilled platypus of Australia.

Pterosaurs
210 million years ago the aerial reptiles - pterosaurs appeared. They were adapted to flying but they could also run. They had beak-like heads and jaws armored with teeth. Their wing reminded that of a modern bat but they differed in the stucteure as they constituted of a leathery patagium stretched between the fourth, elongated digit and the body. The bones of the flying reptiles were hollow. Pterosaurs included rhamphorhynchoids and pterodactyls.

JURASSIC (210-140 million years ago)
The cycads and the conifers were common. First angiosperms appeared. Reptiles dominated the air, the land and the sea. Dinosaurs became numerous. Among quadrupedal and herbivorous dinosaurs there were Apatosaurus with a length of some 20 meters (60 feet), Diplodocus and Brachiosaurus each exceeding 27 meters (80 feet) in length. Quadrupedal armored Stegosaurus was also herbivorous.

Photos of Archaeopteryx, Ichtyosaur and Stegosaurus courtesy of Museum of Evolution in Warsaw

The marine reptiles
The marine reptiles included Ichthyosaur and Plesiosaur. They reminded some of our marine animals. Ichtyosaur had a pointed snout well endowed with teeth. They attained 10 meters (30 feet) length and had both candal and dorsal fins. Other animals which appeared for the first time included true lizard, crocodile and small frog.

Archaeopteryx.
The early bird Archaeopteryx appeared. This bird constitutes a connecting link between the reptiles and the birds. It had a head similar to that of a bird, wings and feathers. The three clawed digits that occurred at the end of thewings, the possession of teeth in both of its jaws and its elonged bony tail signified of the reptilian origin.

courtesy of Museum of Evolution in Warsaw

CRETACEOUS (149-66 million years ago)

The number of gymnosperms decreased and angiosperms came into dominance. The first monocots appeared. Hardwood forests developed. They mainly consisted of magnolias, oak and maple.

Dinosaurs
Dinosaurs diversified into new groups, including duch-billed dinosaurs: for example Barsboldia and Parasaurolophus which was bipedal and herbivorous, armored ankylosaurs, the dome-headed pachycephalosaurs and horned ceratopsians. Protoceratops is numbered among the last group. Perhaps the most powerful dinosaur was the bipedal and carnivorous Tyraunosaurus rex. It was 7 meters (20 feet) high and 17 meters (50 feet) length. Tyranosaurus rex is numbered among the same group with Tarbosaurus.

courtesy of Museum of Evolution in Warsaw

Galimimus was also carnivorous. It nourished with with little invertabrates and vertebrates. Its toothless jaw was covered with a beak. Opisthocelicaudia was a herbivorous giant, that attained up to 30 meters (more than 90 feet). The biggest individuals could weight up to 80 tons (80,000 kilos). The ichtyosaurs and the pterosaurs disappeared. The last pterosaurs achieved up to 12 meters (40 feet) wingspan.

courtesy of Museum of Evolution in Warsaw

The only reptiles that reminded were crocodiles, snakes and lizards. Up to now the mammals had played only a small role being overshadowed by reptilian giants. The triassic proto-mammals were succeeded by the archaic mammals. These mammals had long heavy tails. Their limbs were short and each foot had five digits. They were carnivorous. At the end of the Cretaceous there was a mass exinction, that caused dinosaurs extinction.

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Links:
http://www.paleo.pan.pl/museum/museum.htm