Experts believed that a specific type of marine animal (or “living organism”) had been extinct for 273 million years but a recent discovery has completely reversed that theory. On the floor of the Pacific Ocean, off the coasts of the Japanese islands Honshu and Shikoku, non-skeletal corals were found growing from the stalks of crinoids (also known as sea lilies).
Back in the Paleozoic Era, the ocean floor had large amounts of corals growing on crinoid stems. However, they were believed to have become extinct about 273 million years ago. While different types of corals and crinoids appeared during the Mesozoic Era – after the Permian-Triassic Extinction event – they didn’t have the same relationship as those during the Paleozoic Era.
However, everything changed recently when scientists discovered something absolutely jaw-dropping about 100 meters (328 feet) underneath the surface of the Pacific Ocean. They found two species of coral: the extremely rare hexacorals of the genera Abyssoanthus, and a type of sea anemone called Metridioidea that were both growing from Japanese sea lily stems (Metacrinus rotundus).
Fossilized crinoid
Experts from Poland and Japan made this discovery by studying and photographing the specimens with stereoscopic microscopy equipment. Additionally, they scanned the specimens with non-destructive microtomography equipment in order to see inside of them and identify them with DNA barcoding.
They noticed that the corals attached themselves underneath the crinoids’ feeding fans so they probably didn’t fight for food. Furthermore, since the corals were non-skeletal, they more than likely didn’t have any effect on the crinoids’ stalk movement.
This new discovery also sheds light on a large gap in the records of these specimens. For example, corals from the Paleozoic Era had calcite skeletons, but the ones recently found did not. In fact, soft-bodied organisms like non-skeletal corals are very rare. With that being said, it’s very possible that since the corals don’t affect the crinoids and since they don’t leave any fossils behind, maybe these two have had a long-lasting relationship and hasn’t been recorded in hundreds of millions of years.
Coral
The researchers wrote in part, “The coral-crinoid associations, characteristic of Palaeozoic benthic communities, disappeared by the end of Permian, and this current work represents the first detailed examination of their rediscovery in modern seas.” Since only a small amount of the specimens have been discovered so far, experts are hoping to eventually find more of them and gather more information about their interesting and very long history. (Pictures can be seen here.)
Their research was published in Palaeogeography, Palaeoclimatology, Palaeoecology where it can be read in full.
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