Jongor Series by Robert Moore Williams, Giuseppe Lippi

Ann Hunter, wealthy New York socialite, receives news of her brother's capture by natives while exploring the unknown reaches of Australia. Her brother being the only family she has left, she immediately mounts a rescue mission, which seems doomed to failure when her carriers desert her and she finds herself in a land roamed by dinosaurs and ruled by a lost race with technology far beyond her imagining... moreAnn Hunter, wealthy New York socialite, receives news of her brother's capture by natives while exploring the unknown reaches of Australia. Her brother being the only family she has left, she immediately mounts a rescue mission, which seems doomed to failure when her carriers desert her and she finds herself in a land roamed by dinosaurs and ruled by a lost race with technology far beyond her imagining. Her party only escapes certain death due to the intervention of a mysterious grey-eyed stranger who has survived in this world alone since he was a little boy. He calls himself Jongor, and feeling drawn to Ann Hunter, he vows to help her find her missing brother and escape from Lost Land! less

The third in the Jongar series, a kind of Tarzan of the Lost Land novel.