Plesiosaurus

Plesiosaurus was a large marine reptile that lived during the early part of the Jurassic period. It was distinguished by its small head, long and slender neck, broad turtle like body, a short tail, and two pairs of large, elongated paddles. The plesiosaurus shown in Carnival of Monsters was brownish green and was mildly aggressive. It was intelligent enough to be controlled by the miniscope.

It's unknown how the plesiosaurus was caught in Vorg's miniscope. It's possible the Lurmans or the original owners of the miniscope had time travelling capabilities.