It seems that in japan people is talking about a weird illustration of a youkai that resembles a lot showa era Godzilla, thing being that the illustration was made in 1860s, almost 100 years before Godzilla’s debut in Gojira (1954).

Called Hōnengyo, this monster was said to be a giant fish that lived at the bottom of deep rivers, though it looks more like an amphibian than a fish, it was most likely a loose description of a japanese giant salamander.

About the Images:

The first one is apparently the real Illustration that is now trending in Japan.

The second and third one are also images I found that seem to be old illustrations of said creature but Im not sure? Excuse me for my lack of knowledge in japanese.

The 4th and 5th are some cool sculptures I found online.

The final image is from yokai.com, were I got most of the info. Is a site I highly recommend!