A Brief History of Dinosaurs
Greek deinos, meaning "terrible" or "fearfully great," and sauros, meaning "lizard" or reptile." Scientists classify dinosaurs into two orders — Saurischians and Ornithischians — based on the structure of the bones in their hips.
Most of the well-known dinosaurs — including Tyrannosaurus rex,Deinonychus and Velociraptor — fall into the order known as Saurischian dinosaurs (pronounced sor-ISK-ee-en). These "reptile-hipped" dinosaurs have a pelvis that points forward, similar to more primitive animals. They are often long-necked, have large and sharp teeth, long second fingers, and a first finger that points strongly away from the rest of the fingers.
Saurischians are divided into two groups – four legged herbivores called sauropods and two-legged carnivores called theropods (living birds are theropods).
Theropods walked on two legs and were carnivorous. "Theropod" means "beast-footed" and they are some of the fearsome and most recognizable dinosaurs — including Allosaurus and T. rex.
Scientists have wondered whether large theropods — such asGiganotosaurus and Spinosaurus — actively hunted their prey, or simply scavenged carcasses. The evidence points to the animals working together as opportunistic hunters: they would bring down prey, but also eat animals that were lying around. When fossil-hunters found bones with bite marks on them, they wondered if theropods engaged in cannibalism. It appears now that the animals may have scavenged their own kind, but they didn’t hunt down their own.
Sauropods were herbivores with long heads, long necks and long tails. They were among the largest land animals ever, but they likely had small brains. The gentle giants like leaf-eating Apatosaurus,Brachiosaurus and Diplodocus are part of this family.
Ornithischia
Ornithischian (pronounced or-neh-THISK-ee-en) dinosaurs, a group that includes horned and frilled Triceratops, spiked Stegosaurus and armored Ankylosaurus, are more mild-mannered, plant eaters.
These dinosaurs were beaked herbivores. Smaller than the sauropods, the ornithischia (meaning “bird-hipped”) often lived in herds and were prey to the larger species of dinosaurs. Interestingly, the ornithischia shifted from a two-legged to a four-legged posture at least three times in their evolutionary history and scientists think they could adopt both postures early in their evolutionary history.
Marine reptiles
During the age of the dinosaurs, a lot was happening below the surface of the world’s oceans. The "fish flippers," or ichthyopterygia, includesIchthyosaurus — the streamlined, tuna- and dolphin-shaped ocean-going predators. This abundant family of marine reptiles largely went extinct at the end of the Jurassic Period.
Most of the well-known dinosaurs — including Tyrannosaurus rex,Deinonychus and Velociraptor — fall into the order known as Saurischian dinosaurs (pronounced sor-ISK-ee-en). These "reptile-hipped" dinosaurs have a pelvis that points forward, similar to more primitive animals. They are often long-necked, have large and sharp teeth, long second fingers, and a first finger that points strongly away from the rest of the fingers.
Saurischians are divided into two groups – four legged herbivores called sauropods and two-legged carnivores called theropods (living birds are theropods).
Theropods walked on two legs and were carnivorous. "Theropod" means "beast-footed" and they are some of the fearsome and most recognizable dinosaurs — including Allosaurus and T. rex.
Scientists have wondered whether large theropods — such asGiganotosaurus and Spinosaurus — actively hunted their prey, or simply scavenged carcasses. The evidence points to the animals working together as opportunistic hunters: they would bring down prey, but also eat animals that were lying around. When fossil-hunters found bones with bite marks on them, they wondered if theropods engaged in cannibalism. It appears now that the animals may have scavenged their own kind, but they didn’t hunt down their own.
Sauropods were herbivores with long heads, long necks and long tails. They were among the largest land animals ever, but they likely had small brains. The gentle giants like leaf-eating Apatosaurus,Brachiosaurus and Diplodocus are part of this family.
Ornithischia
Ornithischian (pronounced or-neh-THISK-ee-en) dinosaurs, a group that includes horned and frilled Triceratops, spiked Stegosaurus and armored Ankylosaurus, are more mild-mannered, plant eaters.
These dinosaurs were beaked herbivores. Smaller than the sauropods, the ornithischia (meaning “bird-hipped”) often lived in herds and were prey to the larger species of dinosaurs. Interestingly, the ornithischia shifted from a two-legged to a four-legged posture at least three times in their evolutionary history and scientists think they could adopt both postures early in their evolutionary history.
Marine reptiles
During the age of the dinosaurs, a lot was happening below the surface of the world’s oceans. The "fish flippers," or ichthyopterygia, includesIchthyosaurus — the streamlined, tuna- and dolphin-shaped ocean-going predators. This abundant family of marine reptiles largely went extinct at the end of the Jurassic Period.
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