Fossil marine union has been going on for 273 million years.
Palaeontologists have rediscovered a symbiotic relationship between two deep-sea animals thought to have vanished from the fossil record hundreds of millions of years ago.
The ancient pair discovered in a new study published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology are two types of non-skeletal coral and crinoid, or sea lilies, an animal related to starfish and sea urchins in the phylum Echinodermata.
These specimens were discovered by a team of researchers from Poland and Japan off the coasts of Honshu and Shikoku in the Pacific Ocean. While similar corals and crinoids have been found throughout the fossil record, their symbiotic relationship was thought to be lost after the Paleozoic era.
Their entanglement is caused by coral attaching itself to the crinoid’s stalk-like body, just below their feeding-fan appendage. It provides an ideal environment for coral to thrive and grow, allowing them to eventually reach greater depths. The two coral fossil and crinoid species in question were once abundant on the prehistoric seafloor, but they became extinct. Other versions of the two animals survived separately, and scientists assumed the two had broken things off for food since those specific species had died out.
Scientists recently discovered two known types of coral, a rare type of hexacoral and the Metridioidea sea anemone, hugging the stem of a Japanese sea lily at depths of 330 feet, fossil indicating that their relationship had, in fact, outlasted the last few millions years.
It’s unclear what the crinoids gain from this symbiotic relationship as corals ascend the sea column, but the couple has clearly evolved, according to researchers. The crinoid’s skeletal structure had to adapt to the coral’s fossil attachment in their first iteration. The improved duo, on the other hand, can settle in without the crinoid having to make any physiological sacrifices.
So, congratulations to this dedicated couple, and may we all find crinoids in our corals.