Some sea turtles have spikes in their mouths and throats.

We tend to think of sea turtles as calm, docile creatures that represent the vast serenity of the sea — but then, most of us have never seen the inside of their mouths. Many sea turtles have sharp spikes known as esophageal papillae in their throat, which help them with one of their favorite activities: eating jellyfish. 

Those backward-facing spikes aren’t teeth, however; they’re made of keratin and essentially act as a filter that guides jellyfish into their stomach and prevents them from stinging the turtle’s throat along the way. Sea turtles tend to ingest a lot of seawater when feeding, which they essentially vomit back up once they’re done, and the papillae ensures their food isn’t expelled along with it.