Tegus are reptiles confirmed to appear in Additional Creatures: Endemics.
Tegus are a type of lizard that can be found in South America. There are 8 species of Tegu, which vary in size and lifestyle. While looking very similar to Monitor Lizards, they are not actually related to monitors. It's believed to be a matter of convergent evolution. Tegus are in the same family as caiman lizards and whiptails.
The design of the Tegu has been revealed, but that is all that is known as of now for its addition into Additional Creatures.