Newly discovered fossils give a whole new meaning to jumbo shrimp

The Moroccan desert was once a sea filled with free-swimming arthropods.
Large fossilized fragments of free swimming arthropods
Large fossilized fragments of free swimming arthropods, relatives of modern shrimp and insects. Bertrand Lefebvre

Morocco is making headlines for more than just its incredible run at this year’s World Cup. A new fossil find at Taichoute in the country’s fossil-rich Fezouata Shale formation in southeastern Morocco’s Zagora region is filling in some gaps in evolutionary history.

Fezouata Biota is a the name of a unique assembly of fossilized animals from the Early Ordovician period found in this area which includes radiodonts, lobopodians, nektaspidids, and marrellomorphs. The greater Fezouata Shale formation is home to the remains of numerous large “free-swimming” arthropods that dominated the Earth’s seas about 470 million years ago. These are the relatives of present day shrimp, insects, and spiders.

A study published today in the journal Scientific Reports describes the early evidence found at the site. While more research is needed to analyze these fragments, the giant arthropods could be up to six and a half feet long, a new meaning to the term jumbo shrimp.

[Related: World’s Oldest Fossils Show Sulfur-Based Microbes Lived 3.4 Billion Years Ago, Presenting a New Target for Astrobiology.]

The team says the findings at Taichoute open up new avenues for studying paleontology and ecology.

“Everything is new about this locality—its sedimentology, paleontology, and even the preservation of fossils—further highlighting the importance of the Fezouata Biota in completing our understanding of past life on Earth,” lead author Farid Saleh, a paleontology PhD student at the University of Lausanne and and Yunnan University, said in a statement.

This site and its fossil record are very different from other previously described and studied Fezouata Shale sites, according to the team that represents multiple countries. At the other sites, located about 50 miles away from Taichoute, researchers have found fossils from after the Cambrian Explosion.

The newly discovered site from the Fezouata Shale. Bertrand Lefebvre

“While the giant arthropods we discovered have not yet been fully identified, some may belong to previously described species of the Fezouata Biota, and some will certainly be new species,” Xiaoya Ma, a co-author and palentologist from the University of Exeter and Yunnan University, said in a statement. “Nevertheless, their large size and free-swimming lifestyle suggest they played a unique role in these ecosystems.”

The fossils discovered in this rocks include harder shells and some well-preserved soft body parts such as internal organs. These discoveries help scientists investigate the anatomy of early animal life on Earth and how it has changed over time. The animals here lived in a shallow, stormy, and wavy sea that buried their remains and preserved them in place. However, the free-swimming (or nektonic) animals are actually a relatively minor component overall in the Fezouata Biota. 

[Related: A Scottish fossil is helping scientists fill the gaps in the lizard family tree.]

This new study finds that the Taichoute fossils are preserved in sediments that are a few million years younger than other discoveries from the Zagora area and are dominated by fragments of the giant arthropods. Underwater landslides further delivered the carcasses of these animals to the deeper marine environment.

“Animals such as brachiopods are found attached to some arthropod fragments, indicating that these large carapaces acted as nutrient stores for the seafloor dwelling community once they were dead and lying on the seafloor,” said Allison Daley, a co-author paleontologist the University of Lausanne, in a statement.

Even for seasoned paelentologists, these new species are a surprising find, according to the team.

“The Fezouata Biota keeps surprising us with new unexpected discoveries,” Bertrand Lefebvre, the paper’s the senior author and a palentologist at the University of Lyon, concluded in a statement.