The world is always abuzz with sounds, many of which human ears simply can’t hear. However, other species have extraordinary adaptations that grant them access to realms of sonic extremes. And some of them don’t even have ears— at least,...

Today, we think of penguins as small-ish, waddling, tuxedo-birds. But they evolved from a flying ancestor, were actual giants for millions of years, and some of them were even dressed a little more casually.

Mystacodon is the earliest known mysticete, the group that, today, we call the baleen whales. But if this was a baleen whale, where was its baleen? Where did baleen come from? And how did it live without it?

Why are there dolphins in rivers, and why do they look... like that? There are a handful of very similar-looking, but somehow unrelated river dolphins around the world. Where did they all come from, and what is it about living in rivers...