Name appears to be a japanese pun on “two” which is fitting for a hybrid nature.

Deutalios was originally going to appear in Godzilla vs Biollante, a genetically engineered cross of fish and rat by a mad geneticist trying to kill Godzilla. Godzilla was going to even eat the entrails of Deutalios after killingthem . Deutalios was removed as the script was overhauled, because it distracted from Biollante’s role in an already very busy plot. Personally I think the issue is that the evil scientist campiness just didn’t work for the overall tone of the Heisei series. Seriously a reporter was going to be interviewing this guy about the monster he made, why isn’t he immediately arrested for unleashing a kaiju on the world? Making Biollante a mistake rather than intentional  was honestly a very good move, and Deutalios would made that an impossibility unless they changed the origin which would render the plot even more busy.

Deutalios role  in any future film , be it ally or enemy is probably best used as a harbinger of things to come. Whether it survives a fight with Godzilla or not, or if they don’t fight at all, it sets the stage for more artificial kaiju and signals a huge possible change in the direction of the setting.

On a lighter note, perhaps it could  be young at time of discovery/unveiling as a and become a background baby monster inhabiting monster island. 

I am ambivalent on the design, but think it could benefit from Zebrafish elements. Zebrafish are one of the main fish used in genetics and disease research, so it could be a nice reference: after all if you were making your first kaiju you probably would use the two most well studied lab animals on the planet. Below is a normal zebra fish, and a transparent zebra fish bred to make it easier to see the internal effects of disease.

Sketch Menagerie: Kaiju Unmade Edition by Enshohma.