The Classification of Hybrid Dinosaurs is any Dinosaur that was not a thing of nature but rather a combination of multiple creatures put together into a single beast, hence the term.
As of now, only three official hybrids exist in the game so far, with the Avinychus being the most recent edition in the category (although some skins may also technically be considered hybrids, depending on the skin. For example, the Grizzly Spinosaurus is a hybrid of the Spinosaurus and the Grizzly Bear but it is not considered its own independent species as they are still just skins and not separate dinosaurs.)
In order of when they were added to Dinosaur Simulator.
- Albino Terror A mix of Tyrannosaurus rex, Velociraptor, Allosaurus, Giganotosaurus, Majungasaurus, Rugops, Therizinosaurus(claws), cuttlefish, tree frog, pit viper. – A large hybrid that IS the Indominus Rex (but due to issues to copyright, the devs changed the name). It has the most defense of the three hybrids.
- Megavore A mix of Tyrannosaurus rex, Stegosaurus, Spinosaurus, a spider, Diplodocus and a dromaeosaurid of some kind(foot) and possibly a Metriorhynchid or Mosasaurid. A semi-aquatic monster armed with vicious claws, spikes, teeth, and horns. It has the most health of the three, though it lacks in damage.
- Avinychus A mix of Dilophosaurus, Carnotaurus, Balaur, Baryonyx, Utahraptor, and Pegomastax. – A vicious hybrid that's exceedingly fast unlike the other two. It can glide and sprint and easily chase down smaller foes. It has the most damage of the three, though it lacks in health.