The Ural Mountains and the Caucasus Mountains.
Six:
1. Upper Mississippi
2. Arkanas River
3. Illinois River
4. Missouri River
5. Ohio River.
6. Red River
Answer:
eoraptor
Explanation:
this is kinda controversial so yeah. anyways, this was one of the deepest and was kinda small when archeologist found it. they think it was on earth about 231 million years ago.
source(s)
https://www.smithsonianmag.com/science-nature/scientists-discover-oldest-known-dinosaur-152807497/#:~:text=Art%20by%20Mark%20Witton.,as%20the%20earliest%20known%20dinosaur.
