Its not like Latin had phylogenetics, I've always heard that "saur" can also refer to pretty much any reptile, I suspect if the Romans had knowledge of tuataras, they'd use the term "saur" too.
(That's Greek anyway, not Latin.)
I'm not sure what the [Greeks] would have called salamanders/amphibians/crocodiles (would "saur" apply to any of those?
Not to salamanders, AFAIK; the word _salamandra_ is Latin, BTW. Crocodiles... I hear they were occasionally included; anyway, _krokodeilos_ is said to mean "pebble worm".
However, I'm quite sure that nobody who spoke [Ancient Greek] as their native language would have used the term "saur" to describe Basilosaurus (if they saw a living one)
That's for sure, but *B.* was thought to be a giant snake when it was named, IIRC.