Are all lizards dinosaurs

The "-saur" part does refer to lizards, but the creatures were rather misnamed. In most respects, they were not very lizard-like, but hard more in common with birds.

There was an effort a few years back to refer to them as "Archisaurs," a category meant to include birds and crocodiles and EXCLUDE skinks and iguanas and varanids, but I haven't heard much of it lately.

Most obvious difference: lizard legs sprawl out to the sides, like turtle legs; dinosaur legs are directly under the body weight like birds, elephants, dogs and people.

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''Sauria'' is a Greek Word that means, as noted above, ''lizard''. When dinosaur fossils were first discovered, biologist Richard Owen coined the term Dinosaur, meaning terrible lizard. He knew that the fossils were not those of mammals and that they resembled reptiles more closely than anything else, hence the name.

The term ''Archosauria'' applies to a bona fide Clade and is still in use today. It refers to a group of diapsid amniotes whose living representatives are the birds and crocodilians. It also includes many extinct reptiles such as pterosaurs, some long-gone relatives of crocodilians, and the non-avian dinosaurs.