The dinosaurs
For 165 millions years, life on Earth was dominated by the most spectacular
animals that have ever existed - the dinosaurs.
The Mesozoic Era was a high point in the history of life , because it was the age of dinosaurs. These fantastic creatures in included the biggest, heaviest , and most terrifying of all land animals. They evolved into an amazing variety of forms ranging from huge, armoured leaf - eaters to nimble, feathered hunters, and gave rise to the birds that still flourish today.
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| Photo by Alvaro Reyes on Unsplash |
Family tree
All the dinosaurs of the Mesozoic Era except the very earliest species belonged to two main groups known as the orinithischians and saurischians. The ornithischians evolved into three main types that were nearly all plant - eaters. The saurischians were divided into the mainly meat - eating theropods and the big, plant - eating sauropodomorphs.
Ornithischians
The word ornithischians means "bird - hipped" . It refers to the way that the pelvic bones of these dinosaurs resemble those of birds. The ornithischians also had beak supported by special jawbones. But confusingly the birds themselves are small theropod dinosaurs, part of the saurischian group.
Three type of ornithischians
- Marginocephalians
- Ornithopods
- Thyreophorans
Marginocephalians
These consisted of ceratopsians, like this Pentaceratops with its huge horned neck - fill , and panchycephalosaurs with very strong , armoured skulls.
Ornithopods
One of the most successful groups of dinosaurs, the ornithopods ranged from lightweight animals that ran on two legs to heavyweights like this Muttaburrasaurus. They were all plant - eaters.
Thyreophorans
The thyreophorans included the heavily armoured ankylosaurs and stegosaurs such as this spiny Kentrosaurus.
Saurischians
The saurischian dinosaurs of the early Mesozoic Era had pelvic bones that resembled those of lizards, so the saurischian means " lizard - hipped". But many of later forms evolved bird - like pelvic bones, which the birds were inherit. Saurischians also had longer, more flexible necks than the ornithisschians.
Two types of saurischians
- Theropods
- Sauropodomorphs
Theropods
Spinosaurus was one of the biggest theropods - the group that included all the powerful hunters. They all walked on their hind legs, and many had feathers.
Sauropodomorphs
The sauropodomorphs included the biggest dinosaurs - colossal animals such as Brachiosaurus. They were all plant - eaters that supported their immense weight on four piller - like legs resembling those of elephants. They had very long necks, which were often balanced by equally long tails.
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