A whitish layer striating the Arctic cliffs of Spitsbergen provides exceptional testimony to the regenerative capacity of the living world.
This accumulation of bones, 249 million years old, captures the precise moment when marine life regained its dynamism after the worst biological crisis on our planet. The thousands of fragments discovered tell of the rapid emergence of a complex ecosystem in an environment that had been devastated.
This major discovery challenges established scenarios regarding ecosystem recovery after the end-Permian mass extinction. The work published in
Science by Scandinavian paleontologists demonstrates that marine rebirth was a rapid process rather than a slow reconquest. The methodical analysis of this exceptional deposit opens a unique window onto a key period in Earth's history.
Marine ecosystem of tetrapods dating back 249 million years.
Grippia longirostris, a small ichthyopterygian, hunts ammonoids similar to squids (top left).
The marine amphibian Aphaneramma catches the bony fish Bobastrania (foreground).
The gigantic ichthyosaur Cymbospondylus prowls in the depths (bottom right).
These fossils were discovered on the island of Spitsbergen, in the Svalbard archipelago.
Credit: Robert Back. Biodiversity in a hostile environment
The configuration of the area during the Early Triassic corresponded to high latitudes, bathed by the cold waters of a border ocean of Panthalassa. Conditions were considered difficult for the development of a diverse fauna. Yet, the Spitsbergen deposit reveals a surprisingly rich marine community, with predators of different sizes occupying different ecological niches.
The excavation method used, organized in one-meter squares covering 36 square meters (about 388 square feet), enabled a systematic collection of all fossil elements. This rigor ensured the preservation of fragile clues such as fish scales and coprolites (fossilized droppings). The detailed study of these remains reconstructed the trophic relationships within this ancient ecosystem.
Among the most significant discoveries is the presence of ichthyosaurs of various sizes, including superpredators exceeding 5 meters (about 16 feet) in length. These marine reptiles coexisted with archosauromorphs, related to modern crocodiles, and various species of amphibians. This coexistence demonstrates an ecological complexity that scientists had not suspected for this period.
Implications for understanding biological crises
Precise stratigraphic dating places this fossil deposit at only 3 million years after the Permian-Triassic mass extinction. This short interval contradicts the hypothesis of a marine recovery spread over 8 million years. The speed of this reconstruction questions evolutionary models concerning the adaptation of vertebrates to the marine environment.
The comparative analysis conducted on a global scale positions the Spitsbergen deposit among the most diverse assemblages of Early Triassic marine vertebrates known to date. This richness shows that marine reptile lineages may have an older origin, even predating the mass extinction. The crisis would thus have accelerated their radiation rather than initiated their appearance.
The remarkable concentration of fossils in the same geological level indicates that this ecosystem developed over a short timescale. This preserved snapshot offers scientists a unique case study for understanding post-crisis recolonization mechanisms. The lessons from this distant past shed light on ecological dynamics in the face of environmental disturbances.
To go further: What is the Permian-Triassic extinction?
This biological crisis, which occurred 252 million years ago, represents the most severe in Earth's history. It eliminated approximately 95% of marine species and 70% of terrestrial vertebrates.
The main trigger was massive volcanic activity in Siberia, releasing enormous amounts of greenhouse gases. The resulting global warming caused acidification and deoxygenation of the oceans.
Marine ecosystems were particularly affected, with the collapse of coral reefs and the disappearance of many invertebrate lineages. Complete recovery took several million years, but new discoveries show that it began more quickly than estimated.
Article author: Cédric DEPOND