Monsters used during the late first season and early second season are NOT Sentai monsters. These costumes and their footage was produced by TOEI, exclusively for use by Saban for Power Rangers.
This fiasco created some interesting problems. During the second season and early third season, many monsters from Zyu2 returned over and over AND OVER again because Saban really wanted his money's worth. (More on Zyu2)
Also, the TOEI-made footage for these monsters featured battles between the Dinozords and the monsters in zord fights. That worked fine at the end of the first season, but after the Dinozords were destroyed, Saban had more monsters left. This is why the Thunder Megazord & White Tigerzord never made contact with the monster suits listed above during the zord fights. Stupid, huh?
Zyu2 Monster Costumes That Appeared In America: Bloom Of Doom, Commander Crayfish, Dramole, Fighting Flea, Goo Fish, Grumble Bee, Guitardo, Invenusable Flytrap, Jellyfish Warrior, Lizzinator, Mantis, Octophantom, Oysterizer, Peckster, Pirantishead, Primator, Pumpkin Rapper, Robogoat, Rhinoblaster, Saliguana, Slippery Shark, Soccadillo, Stag Beetle, Two Headed Parrot, Turban Shell.