Here, in The Lost World (1960), they apparently used a young alligator...
And some other reptile here...
Note the two people off to the left in this "split shot" below.
...is that David Heddison from Voyage to the Bottom of the Sea?? “Seaview”?
Who can forget ONE MILLION YEARS BC (1940)! Victor Mature and Carol Landis.
Side by side photos of Landis(1940) and Raquel Welch(1966) causes primitive urges that at my age that I can’t remember why!
The dinosaur lizards were also nice.