What is a Dinosaur?

"First Day of Class" material for a college-level introductory dinosaurs course.
For more info, please check out PBS' "It's Okay To Be Smart" episode called What is a Dinosaur and What Isn't a Dinosaur?    • What Is A Dinosaur And What Isn’t a D...  
Materials used for educational purpose only, but I will try to cite as many artists here as possible:
Fuzzy guy at 22:30 by the amazing Emily Willoughby
Ceratopsian herd at 32:30 by Kayomi Tukimoto
At about 12:34, it should be noted that dinosaurs ARE archosaurs, along with crocodilians and pterosaurs. I believe I meant to say "pseudosuchian" here instead of archosaur when talking about a group that is related to dinosaurs but again are not dinosaurs.