Manda-Stropheus

Manda as a Tanystropheus.

Can't say that Manda's long/chinese dragon design was not as impressive when placed in the same setting as Godzilla or Ghidorah. I felt like tanystropheus was a nice fit. Serpentine, aquatice, reptillian, toothy.

The neck was originally going to be a lot longer, but it didn't sit right with me.

Baragon's Kids

So after being used for Frankenstein Conquers the World, the Baragon suit was used to make the monsters Pagos, Neronga, Gabora, and Magura for the Ultraman series. So it’s a little bit like he has descendants. Sea Baragon and 2001 Baragon are thrown in for good measure.

Godzilla-Raptor

Godzilla as a Dromaeosaur 

Don't get me wrong, feathers are an important part of depicting any kind of raptor, and most theropod dinosaurs. I just like the idea that being mutated by an atomic blast burned all his feathers off and they grew back sparsely and in weird ways.

Almost didn't do this one, on account of a Godzilla with raptor features could just end up being Zilla/Gino/Godzilla1998. Adding Godzilla's distinctive low center of gravity as well as (hopefully) appropriately positioned raptor arms helped move it along.

Guiron and Pups

Anguirus 1998

American Anguirus

Anguirus as a mutated Red Eyed Crocodile Skink, mutated by atomic testing in French Polynesia, ala Zilla and Baragon 1998. I'll leave it up to you to figure so many exotic lizard species were affected by it.

In 1998 American Godzilla movie, Godzilla's name is depicted as a mispronunciation of the original name Gojira, which in the film's world is derived from a Japanese "mythological sea dragon that filled their hearts with fear". This certainly was meant to be some filler text to justify the movie's title name, and, but what if there was more to it? What if in the movie's setting it's part of an international disinformation campaign to cover-up an occurrence in 1954 Japan, the events of the original Godzilla movie? Or what if in this world Godzilla and all associated monsters are actually elements of east Asian mythology, with Gojira literally being a dragon/lóng? What if they weren't just myths?

Anyways, the idea is that this Anguirus got his name because he's buddies with Zilla Junior, and in the myth, Gojira's ally had the same name.

Plateo-Zilla

Godzilla as a Plateosaur.

One idea I've read is that Godzilla might be derived from some sort of carnivorous or omnivorous plateosaur, sort of like the inverse of therizinosaurs. An interesting idea.

I was surprised to learn while researching for this that prosauropods aren't really a scientifically classified clade anymore. They've been absorbed into the sauropodomorph suborder.