Dinosaurs

Dinosaurs were animals that lived 200-250 million years ago. Some dinosaurs were more like reptiles while others were more bird-like.

Although many creatures are sometimes called dinosaurs, dinosaurs did not fly or live in the ocean.

Dinosaur Evolution:

• Dinosaurs evolved from other reptiles (socket-toothed archosaurs) during the Triassic period, over 230 million years ago.
• Dinosaurs evolved soon after the Permian extinction, which was the biggest mass extinction that ever occurred on Earth.
• During this time (the Triassic period), the mammals also evolved.

Why did they go extinct?

Biology of Dinosaurs:

Biology	Description
Size	Dinosaurs ranged in size from the size of a chicken to well over 100 feet long. The longest dinosaurs were sauropods 134 feet long.Smallest dinosaurs wereCompsognathus 2 feet long.
Teeth	Teeth are harder than bone. The number of teeth that dinosaurs had varied widely. Some, like Gallimimus had no teeth. Some had 50 to 60 thick, conical teeth.
Diet	Plant-eaters (herbivores) usually have blunt teeth that are good for stripping vegetation (leaves, twigs, etc.). Meat-eaters (carnivores or theropods) need to have some way to get meat.
Hot blooded Or Cold-Blooded?	Dinosaurs evolved from cold-blooded animals (the reptiles) and evolved into warm-blooded animals (the birds). All dinosaurs, however, were not the same, and perhaps their physiologies differed also.
Dinosaur Fossils, Eggs	Fossils help us understand what the dinosaurs were like. Information can be gathered from sources such as fossilized bones, footprints, eggs, etc.Some of the largest fossilized dinosaur eggs ever discovered were found in China in the mid 1990’s.

How Are Dinosaurs Classified?

Dinosaurs were reptiles from the Mesozoic Era. They are classified as follows:

• Kingdom: Animalia (animals)
• Phylum: Chordata (having a hollow nerve chord ending in a brain)
• Class: Archosauria (diapsids with socket-set teeth, etc.)
• Subclass: Ornithodira (dinosaurs and pterosaurs)
• Superorder: Dinosauria (dinosaurs)
• Order: Saurischia and Ornithischia (based on hip structure)

Types of dinosaur:

Dinosaurs are divided into two orders based on their hip (pelvic) structure:

• The “Lizard-Hipped” or Saurischian dinosaurs.
• The “Bird-Hipped” or Ornithischian dinosaurs.

Types	Description
Saurischian dinosaurs	1. “Lizard-Hipped” dinosaurs had a hip structure similar to that of lizards. They were the ancestors of the birds. 2. The oldest known dinosaurs are from the mid-Triassic period, about 230 million years ago. 3. Saurischians included both meat and plant eaters. 4. Examples: Theropods, Diplodocus.
Ornithischian dinosaurs	1. “Bird-Hipped” dinosaurs had a hip structure that is similar to that of birds. 2. The Ornithischian dinosaurs were vegetarians and included plated, armoured, and horned dinosaurs. 3. Example: Ornithopods, Thyreophora.

Interesting Facts:

• Dinosaurs are a group of reptiles that have lived on Earth for about 245 million years.
• In 1842, the English naturalist Sir Richard Owen coined the term Dinosauria, derived from the Greek deinos, meaning “fearfully great,” and sauros, meaning “lizard.”
• Dinosaur fossils have been found on all seven continents.
• All non-avian dinosaurs went extinct about 66 million years ago.
• There are roughly 700 known species of extinct dinosaurs.
• Dinosaurs Didn’t All Go Extinct at the Same Time.
• Pterosaurs and Marine Reptiles Weren’t Technically Dinosaurs.
• Dinosaurs Lived at the Same Time as Mammals.
• The Vast Majority of Dinosaurs Were Plant Eaters.
• Some Dinosaurs Were Warm-Blooded.
• Dinosaurs Weren’t the First Reptiles to Rule the Earth.