Surprised that I'd never seen this, pretty sure I read the book as a kid. The 1925 film adaptation of H.G. Wells' "The Lost World".
A silent movie, now in the open domain, the reconstruction in sepia and black and white, no shortage of claymation dinosaurs, and, for the time, remarkably well done.
The animator (special effects guru) was Willis O'Brien, who later worked on "King Kong".
Perhaps most remarkable is how precisely the plot is recycled for every single dinosaur movie since - the "Jurassic Park" franchise especially comes to mind.
Worthwhile.