Dinosaur Answers

by Deb on March 16, 2012

Dinosaur

Do you know lots about dinosaurs? Close your eyes and click back for the questions.

1.     Dinosaurs first developed on the supercontinent Pangaea during the Triassic. The most obvious consequence of this is that there was originally one single type of dinosaur fauna because they were not geographically isolated. Remember that dinosaurs lasted for twice as long as it has been since they’ve been gone, so as a group they went through a lot of environmental changes.

During the Jurassic Pangaea began to break up into Laurasia and Gondwana, which further split into the modern continents during the Cretaceous. By then dinosaurs were showing differences, with distinct faunas in Laurasia (Europe and North America), modern China, South America and Australia. North Africa showed similarities to Laurasia which were later replaced by Gondwanic types.

The climate during the Triassic was very hot and dry – the supercontinent formation meant that most land was a long way from the ocean. It was warmer, even the poles were temperate. This was perfect weather for reptiles and allowed them to radiate across the land.

2.     Early dinosaurs were probably meat eaters. It was actually easier for animals to spread onto land than plants, because amphibians had the option of jumping back in when they started drying out. This means most early land animals were meat eaters, because there were more animals around than plants – definitely no enormous grasslands that support today’s huge herbivore herds. Today’s examples of amphibians and reptiles tend to be insectivores or carnivores.

The gymnosperms, or seed-bearing plants such as conifers and cycads spread through the late Triassic, which may have led to the evolution of the gigantic sauropods such as brachiosaurus. Angiosperms or flowering plants spread during the Cretaceous, and are probably linked to lots of different specialisations in herbivorous dinosaurs like the hadrosaurs.

3.     The two main groups of dinosaurs are the ornithischians or bird-hipped dinosaurs, and the saurischians or lizard-hipped dinosaurs. Just to make it extra confusing, birds evolved from the saurischians. This is actually a really unfortunate set of names, because the similarities aren’t as close as they sound. They’re very old, so I suppose we can put it down to poor preservation and understanding of the fossils available at the time.

The ornithischians includes things like the ankylosaurs, stegosaurs and ceratopsians. They are called this because part of the hip called the pubis goes backwards, like it does in birds, but it also has a forward projection that birds don’t have. Saurischians include the theropods, two legged carnivores like raptors and tyrannosaurs, as well as the giant sauropods. Their pubis generally goes forwards, as it does in reptiles, except they are all different and some of them go back as they are becoming more birdlike.

pelvis

This is all looking from the side, but I think the really interesting story is when you look from the front, which I have spent many hours scouring the internet trying to do and finding very, very little on. The reason for the scouring was a hint I had about eggs, and how large they can grow, as well as much experience cooking and eating chickens.

As we know from Kiwis, bird eggs can be very, very large. I finally found the confirmation I was after at the Inner Bird that showed that birds have open pelves and their pubic bones don’t meet at the front. This lets them have relatively large eggs.

Dinosaurs on the other hand, even the ornithischians who supposedly have bird hips, have a solid ring of bone with the pubic bones meeting at the front. They could only lay relatively small eggs, which then limited the ways they could structure their clutches. It had to be lots of little, immature babies, not a few big ones.

bird and dinosaur pelvis

4.     There are actually quite a few things dinosaurs have in common with mammals. It’s a great example of broad convergence because of environment, it has nothing to do with descent. Basically they are both the dominant form of large animal on the planet, so they use similar solutions to exploit similar niches.

  • Dinosaurs were almost certainly warm-blooded. If nothing else, large animals automatically have some temperature regulation because of their size.
  • Later herbivores developed complex teeth and some had cheek-like structures that allowed them to chew plants.
  • They stood upright with their legs underneath them, which allows more efficient breathing and movement.
  • They had extensive parental care and social systems.

5.     That little guy up the top? Velociraptor. Yes, the big baddy of Jurassic Park is actually a little birdlike animal. And it wasn’t because they got confused, it was to make them scarier. Sigh.

This is modified from the BBC series “The Truth About Killer Dinosaurs” and shows a more realistic view of small, feathered but still fearsome velociraptors.

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