Hundreds of three-eyed 'dinosaur shrimp' emerge after Arizona monsoon

A triops is a small three-eyed crustacean found in the Wupatki National Monument's ball court pond.
According to officials from Wupatki National Monument, hundreds of prehistoric-looking creatures emerged from tiny eggs after a severe summer thunderstorm in northern Arizona. They began swimming around a temporary lake in the desert landscape following which they were rescued by hundreds.

Triops, a tadpole-sized creature, is described as "mini-horseshoe crabs" by Lauren Carter, Wupatki National Monument's lead interpreter. According to Central Michigan University, their eggs can lie dormant in the desert for many decades until sufficient rainfall falls to form lakes that allow hatchlings to mature and produce eggs for the next generation.

Triops' appearances were so rare that tourists who reported seeing them in a temporary, water-filled lake inside the monument's ceremonial balls court, a circular walled structure measuring 105 feet (32 m) across, didn't know what to do with the creatures.

Similar: Photos: The ancient sea monster was an arthropod that was the largest in size

Carter stated that after a monsoon in July, Carter knew there was water in the court but didn't expect anything to live in it. "Then, a visitor came up to Carter and said, "Hey, there are tadpoles in your ballcourt."

Carter initially wondered if toads, which live underground burrows during dry seasons, might have emerged during the wet season to lay eggs. Carter went to Wupatki's ballcourt to investigate.

"I picked it up with my hands and looked at it. I was like, 'What's that?' I had no idea," Carter said. She felt a sense of familiarity, as Carter had worked previously at Petrified Forest National Park, northeastern Arizona. Carter also recalled Triops reports there. She said, "And then I had the urge to research it."

After the monsoon of late July, the vernal pool formed in the Wupatki National Monument's ball court. (Image credit: L.Carter/NPS)

Three-eyed crustacean

Triops, Latin for "three eyes", are often called "dinosaur Shrimp" due to their long evolutionary history. Their ancestors evolved during the Devonian Period (419 million to 359 millions years ago) and their appearance has not changed much since then according to Central Michigan University. (Note: The Triassic period, which started around 252 million years ago, saw the first appearance of dinosaurs.

Triops, however, are not exactly the same as their ancestors and therefore they would not be considered "living fossils".

Carter stated, "I don’t like the term ‘living fossil’ because it causes confusion with the public that they haven’t changed at all." They have evolved, but they have changed. They are very similar to what they looked like millions of years ago.

Central Michigan University reports that there are two genera in the Triopsidae Triops, and Lepidurus. Together they could contain up to 12 species. Carter stated that Triops longicaudatus could have been the species of the critters at the Wupatki court. This species is found in short-lived freshwater pools in North, Central, and South America. However, Carter stated that a scientific analysis is required to confirm this.

Image 1 of 2. The Arizona monsoon created a vernal pool at Wupatki National Monument's ball court. (Image credit to NPS. Image 2 of 2. A view of Wupatki National Monument's ball court. Image credit: NPS

According to Central Michigan University, Triops can reach 1.5 inches (4 cm) in length after hatching. They have a shield-like carapace, which looks almost like a helmet. They have large, black-rimmed compound eyes that look like a dragonfly's or bee's. Between them, they also have a small ocellus (or simple eye), and an angry, wise expression. According to the Amateur Entomologists Society, Ocellus eyes are common in arthropods, which include insects, crustaceans, and arachnids. They are filled with simple photoreceptors that enable these creatures to detect light.

Similar Photos: Photos: This ancient shrimp-like creature was small but fierce

The Triops at Wupatki National Monument were blessed with a brief but intense rainy season. Carter stated that Flagstaff, Arizona, which is located just 30 miles (or 50 kilometers) south of the monument, usually receives around 9 inches (22.9cm) of rain per year. Carter stated that Flagstaff experienced its lowest rainfall monsoon season in 2021, receiving just 4 inches (10.2cm) of rain. The region received nearly 5 inches (12.7cm) of rain in the final week and a quarter of July 2021.

According to Central Michigan University's life cycle description, Triops' eggs were laid during that time and the little critters began filter-feeding within hours. They went through several molts, before maturing fully in just over a week, like other crustaceans.

The males and females of triops mate through sexual reproduction. However, in times of shortage, they have other options. These crustaceans are hermaphrodites which means they have both male sex organs and a parthenogenetic. This partnership includes the University of Michigan School of Education and the University of Michigan Museum of Zoology.

Carter stated that triops can live for up to 90 days. However, the pond at Carter's ball court only lasted three to four weeks. She noted that ravens and common nighthawks were quick to notice the fish, and swam into the water to eat them.

It is not known how many Triops were able to lay eggs before the lake dried out. To find out, Rangers will need to wait until the next monsoon.

Original publication on Live Science