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Course: American Museum of Natural History > Unit 1
Lesson 1: What is a dinosaur?- What makes a dinosaur a dinosaur?
- What is and is not a dinosaur?
- What is and is not a dinosaur?
- How do dinosaurs get their names?
- How do dinosaurs get their names?
- Linking birds and dinosaurs
- How do we know which kinds of dinosaurs were most closely related?
- How do we know which kinds of dinosaurs were most closely related?
- Quiz: What is a dinosaur?
- Exploration Questions: What is a dinosaur?
- Answers to Exploration Questions: What is a dinosaur?
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What makes a dinosaur a dinosaur?
A defining feature of a dinosaur like Velociraptor was a hole in their hip socket (a Velociraptor was a carnivorous dinosaur closely related to birds). Other reptiles, such as lizards and crocodiles, have legs that sprawl out to the side, with thigh bones almost parallel to the ground. They walk and run with a side-to-side motion.
Dinosaurs, on the other hand, stood with their legs positioned directly under their bodies. A hole in their hip socket permitted this upright stance, which allowed dinosaurs to run faster and with greater endurance than other reptiles of the same size.
During the Age of Dinosaurs, there were other reptiles living on land and in the seas, including pterosaurs (flying reptiles), and plesiosaurs (ocean-dwelling reptiles). But they did not have a hole in their hip socket and so were not dinosaurs.
Modern birds are classified as a type of dinosaur because they share a common ancestor with non-avian (non-flying) dinosaurs, which became extinct about 66 million years ago. They share features such as the hole in the hip socket, the three-toed foot and the s-shaped neck.
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Want to join the conversation?
- Are there (besides birds) more animals that are still alive nowadays that could be classified as dinosaurs based on the presence of a hole in their hip socket? Any living fossils that match this criterium?(16 votes)
- Nope, all descendants of dinosaurs are classed as dinosaurs or birds. Nothing that isn't descended from a dinosaur found so far has this hole in the hip.(10 votes)
- I know there are two kinds of dinosaur hips. What are the two?(6 votes)
- the answer is to look a dinosaur index on a website(2 votes)
- So, I have a brain teaser for all of you. Why couldn't scientists tell if dinosaurs had feathers or not?(5 votes)
- Would it be because the feathers deteriorated so they couldn't see traces of anything but the bone? Or they were reptiles so they weren't in the class of avian (birds)(12 votes)
- This is the first time I'm in Partner Content AMNH.(3 votes)
- Please put this in tips and thanks I think 😸(3 votes)
- Has anyone found DNA to a velosarapter.(3 votes)
- No, and unfortunately we couldn't make one even if we did(2 votes)
- Did birds as we know them exist alongside dinosaurs before the extinction ?(2 votes)
- Yes, they did! The first Dinosaurs that we now think of as birds appeared about 150 million years ago in China.(3 votes)
- how many species are there?(2 votes)
- At present over 700 different species of dinosaurs have been identified and named. However palaeontologists believe that there are many more new and different dinosaur species still to be discovered.(1 vote)
- what is a life cycle of a Dinosarus?(2 votes)
- Has anyone found the DNA of a pterosaurs? Have they found the DNA of ANY dinosaur? Also, were did dinosaurs live? Evreywhere? Did they live in places like Europe? across the globe?(2 votes)
- why does it depend on the hip bone a megelosaurus has a croc hip(2 votes)