A little controversy about the actual release date on this one.
Made in 1950 for a December release but quite posibly not released unitil January of 1951. The Movie title therefore lists under both years.
Since it was not included in this series 1951 collection, I have included it in this one.

Two Lost Worlds (1950) is a science fiction/adventure film, presenting James Arness in his first starring role (his last name is still spelled "Aurness" in the credits) and Laura Elliott.
The year is 1830. The American clipper ship, the Queen, is attacked by pirates in the Hebrides (present day Vanuatu). The ship's mate Kirk Hamilton (Arness) is wounded and heads to Queensland Colony in Australia for medical treatment. While at the hospital, he meets and falls in love with Elaine Jeffries (Rogers), the fiancee of Martin Shannon (Bill Kennedy) a rancher. A romantic rivalry develops and the pirates, who attacked Kirk and his ship kidnap her along with her friend, Nancy Holden (Jane Harlan). Kirk and Shannon pursue the pirates and they soon wind up on a volcanic island, inhabited by dinosaurs.

There are no original dinosaur effects in the film. The dinosaurs appear 58 minutes into the film during the final reel and were taken from stock footage recycled from the film One Million B.C. (1940).