Why was he credited as Desi Arnaz?
I know that a lot of Juniors will eventually just drop the "Jr." from their name but that is usually well after their father has died (i.e. Lon Chaney Jr. eventually dropped the "Jr." but that was long after his father died and long enough for the general public to have "forgotten" about his father). But in this movie Desi Arnaz Jr. is credited as "Desi Arnaz", the thing is that his father was still very much alive when this movie was released, so I just find it kind of odd that he would be credited as such.
Dragonzord! Mastodon! Pterodactyl! Triceratops! Saber Toothed Tiger! Tyrannosaurus!