Deep-Sea Jurassic Fossils Hint at Role in Evolution

Deep Sea

Newly discovered deep-sea fossils from the Jurassic period suggest that previous thoughts about the role of shallow water evolution need to be modified. These 180 million-year-old fossils represent the oldest known creatures yet found for species of those groups. What is so unique about this finding is where the fossils were found: researchers discovered them in the Austrian Alps.

Years ago, a landslide occurred in the Glasenbach Gorge outside of Salzburg, the fourth-largest city in Austria. It was then that an amateur palaeontologist named Gero Moosleitner started collecting the fossils that he had found in this region. After accumulating these fossils over a period of years, Moosleitner eventually called Dr. Ben Thuy, an invertebrate palaeontologist working at the National Museum of Natural History in Luxembourg.

Thuy and his team examined the site and the fossils, and eventually realized that they were in fact deep-sea species from the Jurassic period. It has been known since at least 1970 that this region was a basin of Jurassic treasures. The alpine rock also bears many similarities to modern rocks found in the depths of the sea. Upon further examination, the research team realized that the organisms in this rock bed were not light-dependent species.

The fossils found came from a number of different groups of organisms, including echinoderms, the order to which modern species like starfish, sand dollars and sea cucumbers belong as well as gastropods, the class containing current day slugs and snails. Some of the specimens in this were around 25 million years older than the previously known oldest fossils of their type, fossils which, like some members of current-day species, were found in shallow water environments. The previous fossil finds led many to believe that species could evolve in those shallow waters and then move into deeper regions. However, the current study reverses that, and hints from these Jurassic fossils instead point to the role of evolution of species in the deep sea which can then move into shallower beds.

This research is important for other reasons as well. First, it suggests that the anoxic events of the Jurassic period – or events where water was lacking in oxygen – were either less widespread than previously thought or less severe. It also shows that the deep-sea was capable of producing higher taxa species than once thought and that these species could be better sheltered in this environment, as they could survive in deep regions even after migration towards and extinction in shallow waters. Finally, it proves that there is a great deal of biodiversity in these regions, more than was originally suspected.

The authors of the current study note that given this biodiversity, mining and trawling activities in the deep sea may have a significant negative impact. Indeed, a separate finding published just a few days before found that area of the depths that had been recently trawled had only about half as much biodiversity as protected regions. These trawled environments also had less than half the amount of organic matter, leading those scientists to worry about affected regions becoming “faunal deserts.” Given that these new Jurassic fossils are hinting at information about both the role of the deep sea in our evolutionary history and also show just how rich an environment it actually is, regulators may wish to reevaluate these activities to help protect what remains of this environment.

By Bryan A. Jones

Scientific American
National Geographic
Proceedings of the Royal Academy

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