Tourists visiting Wupatki National Monument, an indigenous Puebloan site in northern Arizona, recently stumbled upon hundreds of unusual visitors - pre-dinosaur era three-eyed shrimp, following a heavy summer downpour.

Triops, which are the size of tadpoles, "look like little mini-horseshoe crabs with three eyes," according to Lauren Carter, lead interpretation ranger at Wupatki National Monument.

The creatures, sometimes known as tadpole shrimp, have a peachy pink body with a crest-shaped torso that tapers off into a dangly tail and are about an inch or two long.

Data from Central Michigan University says their eggs can remain dormant in the desert for decades until enough rain falls to create lakes, which provide real estate and time for the hatchlings to mature and lay eggs for the next generation.

After a monsoon filled the park's ball court to capacity, the little critters presumably infested it.

Tourists reported seeing triops at a temporary, rain-filled lake within the monument's ceremonial ball court - a circular walled structure 105 feet across - and the monument's staff had no idea what to make of them.

A tourist exploring the area informed Carter about the animals' presence in the rainwater pond. She and the rest of the team eventually deduced that these strange-looking shrimp were freshwater triops called triops longicaudatus. They point out that more research is needed to confirm that hypothesis.

Because of their long evolutionary history, Triops - Greek for "three eyes" - are frequently referred to as "dinosaur shrimp." Their ancestors evolved during the Devonian period (419 million to 359 million years ago), and their appearance has changed very little since then.

It's not rare to come across a few of these creatures in the wild, and some pet stores even sell them, claiming Triops are low-maintenance companions since they only live for approximately 90 days.

The pond at the ball court, however, only lasted three to four weeks, Carter noted. Local birds took notice very immediately, with ravens and common nighthawks swooping down into the lake to devour the creatures, she observed.

It's unclear how many Triops laid eggs before the lake dried up. Rangers will have to wait till the next monsoon to learn more.