Researchers have uncovered fossil fragments of eurypterids, or “sea scorpions,” in the Fezouata Biota near Bni Zoli, near Zagora, in southeastern Morocco, according to research published in the Royal Society Publishing. Carbon dating indicates that the giant arthropods appeared 12–15 million years earlier than previously known.
The fossils include spinose walking appendages assigned to a new species, tentatively named “?Carcinosoma aurorae”, part of the carcinosomatid group. The appendages show alternating long and short ventral spines and heavily serrated gnathobases, indicating a predatory lifestyle. A separate patch of densely scaled cuticle hints at a second, possibly larger eurypterid species.
The Fezouata Biota is a rare Early Ordovician fossil site, dated to around 479 million years ago, during the late Tremadocian stage. Located in the Anti-Atlas region of southeastern Morocco, it has preserved not only hard-shelled creatures like trilobites and brachiopods but also soft-bodied animals, offering a unique window into early marine life. Few people are aware of Fezouata, yet it rivals the Burgess Shale in preserving delicate tissues and revealing the early evolution of marine ecosystems.
These Moroccan fossils show that the major split between swimming eurypterines and crawling stylonurines had already occurred by the Early Ordovician. Carcinosomatids, such as “?C. aurorae,” are highly evolved eurypterines, implying that most eurypterid clades had diversified earlier than the fossil record had indicated.
The discovery also has broader evolutionary significance. Eurypterids are the sister group to modern arachnids, so the early presence of carcinosomatids suggests that spiders, scorpions, and their relatives may have originated far earlier than the Silurian fossil record shows.
Scientists note that eurypterids were likely powerful swimmers, which may explain why their remains are rare in Fezouata, a site dominated by benthic animals. The fragments may represent floating carcasses or molted exoskeletons.
Previously, the oldest eurypterid was Pentecopterus decorahensis from Iowa, US, dating to the Middle Ordovician. The Moroccan specimens now extend the known history of sea scorpions by up to 15 million years, offering crucial insight into the early radiation of chelicerates off Gondwana, rather than the previously assumed Laurussia.
This finding also hints that early marine arthropods had already undergone significant diversification by the Ordovician, supporting the idea that shallow tropical seas served as cradles of evolutionary innovation in the early Paleozoic.
The study of Fezouata continues to reveal unexpected diversity and evolutionary milestones, highlighting Morocco as a key site for understanding the origins of complex marine ecosystems more than 470 million years ago.
