This is a truly terrible film. I am not familiar with the Jules Verne story this is based on, but it is clearly not one of his best, The Hokum science actually made me laugh out loud as did much else.
Neathderthals portrayed as ape men; big busted blonde totty cavegirls and bearded cavemen from two tribes.
As for the monsters - well, reminds me of the end of one version of Journey to the Centre of the Earth where they filmed live lizards near small rocks to made em look big. That is the playbook here except for some bizarre flying dragon thing, parallel evolution 'parently, and some cartoon mammoths.
Tbh I felt really sorry for the animals used. An elephant with fur stuck on to create a little mammoth; a crocodile or smaller caiman more likely with a fin glued to its back which fights a lizard to the death (animals were harmed making this movie!) and a snake killed by a lizard. NOT one for sensitive animal lovers/.
A curiosity piece. 1.5 stars for effort.