One fish, two fish, red fish, blue fish. 
From there to here, from here to there, 
funny things are everywhere.

So wrote Dr. Seuss in his 1960 classic.

But nowhere among the cold fish—the only kind known to Seuss, or to science—was there a warm fish.

Now researchers have discovered that the opah is in fact just that. It pumps heated blood through its body as if it were a mammal or a bird.

It’s a fish even Seuss didn’t imagine.

Dybas, C.L. 2015. Ripple marks—The story behind the story. Oceanography 28(3):16–17, https://doi.org/10.5670/oceanog.2015.72.

This is an open access article made available under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and reproduction in any medium or format as long as users cite the materials appropriately, provide a link to the Creative Commons license, and indicate the changes that were made to the original content. Images, animations, videos, or other third-party material used in articles are included in the Creative Commons license unless indicated otherwise in a credit line to the material. If the material is not included in the article’s Creative Commons license, users will need to obtain permission directly from the license holder to reproduce the material.