The horseshoe crab has some pretty terrifying ancestors, as I have discussed here in the past. It may also have descended from the less-terrifying, more -intriguing trilobites, which went extinct over 100 million years ago after a 300 million-year run. In addition to horseshoe crabs, the trilobites may have developed into horseshoe shrimp, believed to be among the oldest living species on Earth, remaining nearly unchanged for about 200 million years.

It’s also strangely cute:

They are very small, roughly 2 to 4 millimeters in length, which has a great deal to do with their apparent cuteness. If the creature pictured above were, say, the size of a Ford Fiesta, I would not be discussing its cuteness, but rather wondering how I could get my hands on a tank.

Photo credits: “A Noodly Encounter” by jurvetson [CC BY 2.0], on Flickr; DocCrystal on darkcrystal.wikia.com.