Exeter (UK): Giant arthropods, cousins of contemporary species like shrimp, insects, and spiders, may have dominated the oceans 470 million years ago, according to findings at a significant new fossil site in Morocco.
Numerous huge "free-swimming" arthropods are documented in the earliest evidence from the Taichoute site, which was formerly underwater but is now a desert.
The analysis of these fragments requires further study, but based on specimens previously identified, the huge arthropods may reach lengths of up to 2 metres.
The site and its fossil record, according to an international research team, are substantially distinct from other Fezouata Shale sites that have been characterised and researched from a distance of 80 km.
They say Taichoute (considered part of the wider "Fezouata Biota") opens new avenues for paleontological and ecological research.
"Everything is new about this locality - its sedimentology, palaeontology, and even the preservation of fossils - further highlighting the importance of the Fezouata Biota in completing our understanding of past life on Earth," said lead author Dr Farid Saleh, from the University of Lausanne and Yunnan University.
Dr Xiaoya Ma, from the University of Exeter and Yunnan University, added: "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.
"Nevertheless, their large size and free-swimming lifestyle suggest they played a unique role in these ecosystems."
The Fezouata Shale was recently selected as one of the 100 most important geological sites worldwide because of its importance for understanding the evolution during the Early Ordovician period, about 470 million years ago.
Fossils discovered in these rocks include mineralised elements (eg shells), but some also show exceptional preservation of soft parts such as internal organs, allowing scientists to investigate the anatomy of early animal life on Earth.
Animals of the Fezouata Shale, in Morocco's Zagora region, lived in a shallow sea that experienced the repeated storm and wave activities, which buried the animal communities and preserved them in place as exceptional fossils.
However, nektonic (or free-swimming) animals remain a relatively minor component overall in the Fezouata Biota.
The new study reports the discovery of the Taichoute fossils, preserved in sediments that are a few million years younger than those from the Zagora area and are dominated by fragments of giant arthropods.
"Carcasses were transported to a relatively deep marine environment by underwater landslides, which contrasts with previous discoveries of carcass preservation in shallower settings, which were buried in place by storm deposits," said Dr Romain Vaucher, from the University of Lausanne.
Professor Allison Daley, also from the University of Lausanne, added: "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."
Dr Lukas Laibl, from the Czech Academy of Sciences, who had the opportunity to participate in the initial fieldwork, said: "Taichoute is not only important due to the dominance of large nektonic arthropods.
"Even when it comes to trilobites, new species so far unknown from the Fezouata Biota are found in Taichoute."
Dr Bertrand Lefebvre, from the University of Lyon, who is the senior author of the paper, and who has been working on the Fezouata Biota for the past two decades, concluded: "The Fezouata Biota keeps surprising us with new unexpected discoveries".
The paper, published in the journal Scientific Reports, is entitled: "New fossil assemblages from the Early Ordovician Fezouata Biota." —ANI