Experts have revealed what the Ophiojura is, a strange deep-sea animal that was found in 2011 by scientists from the French Museum of Natural History, while dredging the top of a secluded seamount called Banc Durand.
Ophiojura is a species of fragile star with snake-like arms radiating from its body, which lives on the sea floor around the world.
Tim O’Hara, Senior Curator of Marine Invertebrates, Museums Victoria, realized at a glimpse that the animal was remarkable when he first spotted it in 2015. The eight arms were 10cm long each, and armed with rows of hooks and spines. Microscopic examination revealed jagged rows of sharp teeth lining each jaw, which are believed to be used by them to tear apart their prey.
Discovered to live on a seamount in the depths of the Pacific Ocean, Ophiogora is the last known survivor of a unique group of animals that diverged from their closest relatives in the Jurassic period.Tweet embedTim O’Hara explains: https://t.co/9z6N6zUqN0
– ConversationEDU June 16, 2021
With O’Hara and his colleagues now reporting in Proceedings of the Royal Society BHowever, the Ophiojura is indeed a completely unique species of animal not previously described. It is unique – the last known species of an ancient breed, such as the coelacanth or the tuatara.
The researchers compared DNA from a range of different marine species, and concluded that Ophiojura is separate from the closest living brittle star species by about 180 million years of evolution. This means that their most recent common ancestor lived during the Triassic or early Jurassic period, when dinosaurs were just on the way.
(J. Black/University of Melbourne, author provided)
Since then, Ophiojura’s ancestors have continued to evolve, eventually leading to the situation today, where he was the only known survivor of an evolutionary lineage stretching back 180 million years.
Surprisingly, the researchers found small fossil bones similar to our new species in the Jurassic rocks (which are 180 million years old) from northern France, further evidence of their ancient origin.
Scientists used to call animals like Ophiojura “living fossils”, but that’s not entirely true. Living things do not remain frozen over time for millions of years without changing at all. The ancestors of the Ophiojura have continued to evolve, in very subtle ways, over the past 180 million years.
As for seafloor life, the center of ancient endemism is located on continental margins and seamounts in tropical waters from 200 to 1,000 meters deep. And this is where we find the “remnants” of ancient marine life – species that persisted in a relatively primitive form for millions of years.
Seamounts, such as those found by Ophiojura, are usually submerged volcanoes that arose millions of years ago. Lava seeps out of vents on the sea floor, constantly adding layers of basalt rock to the top of the volcano. The volcano could eventually rise above sea level, forming an island volcano like the one in Hawaii, sometimes with coral reefs circling its shores.
But eventually the volcano dies, the cold rocks send chills, and the heavy basalt sinks the seamount into the relatively soft oceanic crust. With enough time, the seamount would subside hundreds or even thousands of meters below sea level and gradually become covered again with deep-sea animals. Its sunlit past is remembered in the rocks as a layer of fossilized reef animals around the summit.
While the new species are from the Southwest Pacific, seamounts are occurring all over the world, and we are just beginning to explore those in other oceans. In July and August, researchers will lead a 45-day expedition aboard the Australian oceanographic research vessel, RV Investigator, to the seamounts around the Cocos (Keeling) Islands in the eastern Indian Ocean.
Source: Science Alert
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