Talk about a prehistoric plot twist.

A 324-million-year-old fossil that spent decades collecting dust in the basement of a California museum has turned out to be one of the earliest known insects on earth, rewriting the evolutionary history of life on Earth.

For 40 years, the prehistoric creepy crawler — specimen No. 28852 — sat tucked away in a drawer at the San Diego Natural History Museum, labeled Tesnusocaris goldichi — another run-of-the-mill ancient shrimp-like crustacean.

Turns out, scientists had it completely wrong.

Thanks to an eagle-eyed Cambridge University PhD student who flew across the pond to inspect the forgotten slab, the museum has slapped a brand new label on the artifact: Chosha praecursor. It’s not a crustacean. It’s an insect.

The stunning reclassification officially crowns the prehistoric critter among the “earliest uncontested insects” ever discovered, the San Diego Union Tribune reported. The discovery reportedly blew open the long mysterious “hexapod gap,” which is a 60 million year blackout in the fossil record during which early bugs seemingly vanished from Earth.

The breakthrough came when Cambridge doctoral researcher Erik Tihelka spotted pictures of the long-overlooked fossil in a textbook and booked a ticket to SoCal to take a closer look himself, according to the San Diego Union Tribune.

The creepy crawler had classic insect features, including six legs attached to its thorax, an egg-laying organ and a tail-like filament extending from its end, while also boasting numerous extra pairs of paddle-like legs jutting out from its abdomen — a crustacean feature.

Scientists reportedly believe the creature may have used its extra paddle legs to glide through the water — offering a rare glimpse into how ancient aquatic ancestors evolved into the insects that crawl and fly across the planet today.

The specimen originally made its way to the Golden State back in 1985, after being brought back from a dig in Brewster County, Texas. It was classified as a crustacean in 1991.

Now, it’s getting the rockstar treatment it deserves. Museum bosses have pulled the evolutionary relic out of the basement and locked it safely inside a glass display case on the museum’s lower level, where visitors can gawk at the creature that bridges the gap from sea to land.

“There is nothing that makes a curator happier than having a researcher use the collection,” Tom Deméré, the museum’s director of paleontology, told the San Diego Union Tribune. “To have a specimen that has been in the collection for 40 years have a new life in the scientific literature, and hopefully in the general public’s mind, shows that new discoveries can be made.”

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