Why are some monsters not listed in credits even though they make appearances?

[Jason]

In Godzilla vs. the Sea Monster, no mention is made of that giant condor monster. Also, in IDW's first issue of Godzilla: Rage Across Time, they don't mention that Japanese monster who never appeared in movies. Also, in the second issue, they don't mention that Hydra monster that Godzilla battled. Why? As long as they're dealing with creatures discussed in ancient writings, I wish they'd do an issue with the seven headed dragon described in the book of Revelation.
God bless, Jason Irelan

[Saansilt]

For IDW those are classical mythical beasties. The monsters listed in the credits are listed there because they were licensed by IDW. You don't need to license mythology.

[Jason]

Okay, but why was the giant Condor not listed in the credits of Godzilla vs. the Sea Monster? I know he didn't do a whole lot, but he did more than Kamoebas did in Godzilla: Tokyo S.O.S. You can't get Toho to didly squat that monster in a Godzilla movie, and I wish they would. You can't get IDW to do anything with that turtle monster either other than use his name in an issue in the past. I'd like to see him in action so I can see how powerful he is as a kaiju.
God bless, Jason Irelan
P.S. Is there any chance they could do a Godzilla vs. Lee Roy Brown story in a comic book issue like Dark Horse did with that basketball player Charles Barclay? According to the lyrics of the Jim Croce song, he's badder than old King Kong, so I'd like to see him battle Godzilla.

[UltramanGoji]

What do you mean "listed in the credits"? Like, the monster icons on the back of the box?

Toho can't copyright the idea of a giant bird. It doesn't have its own character, it has no identity. It's just a big stupid bird. Kamoebas is the complete opposite. He starred in his own movie independent from the Godzilla series and actually had a name.

P.S. Is there any chance they could do a Godzilla vs. Lee Roy Brown story in a comic book issue like Dark Horse did with that basketball player Charles Barclay? According to the lyrics of the Jim Croce song, he's badder than old King Kong, so I'd like to see him battle Godzilla.

Absolutely never going to happen in a thousand millenia and you'd be a fool to think it would.

[Jason]

But Kamoebas is a completely new monster to me. When I saw his name listed in the circles, I thought he was supposed to be some kind of giant amoeba monster until someone from IDW's Godzilla board that I can't find anymore told me he wasn't; and all I heard throughout the whole movie was his name. When I read an essay about Godzilla vs. The Sea Monster in one of the G-Fan issues, I saw the word condor, so I figured that was the bird creature's name.
God bless, Jason Irelan