"Living Fossil" Thought Extinct for 273 Million Years Found Thriving on Ocean Floor
upstart writes in with an IRC submission for c0lo:
'Living Fossil' Thought Extinct For 273 Million Years Found Thriving on Ocean Floor:
A symbiotic relationship between two marine lifeforms has just been discovered thriving at the bottom of the ocean, after disappearing from the fossil record for hundreds of millions of years.
Scientists have found non-skeletal corals growing from the stalks of marine animals known as crinoids, or sea lilies, on the floor of the Pacific Ocean, off the coasts of Honshu and Shikoku in Japan.
"These specimens represent the first detailed records and examinations of a recent syn vivo association of a crinoid (host) and a hexacoral (epibiont)," the researchers wrote in their paper, "and therefore analyses of these associations can shed new light on our understanding of these common Paleozoic associations."
[...] Fossils of soft-bodied organisms - such as non-skeletal corals - are rare. Zoantharia such as Abyssoanthus have no confirmed fossil record, and actiniaria such as Metridioidea (seen as a dry specimen in the image below) also are extremely limited.
If these corals don't modify the host, and leave no fossil record, perhaps they have had a long relationship with crinoids that has simply not been recorded.
This means the modern relationship between coral and crinoid could contain some clues as to Paleozoic interactions between coral and crinoid. There's evidence to suggest that zoantharians and rugose corals share a common ancestor, for instance.
Journal Reference:
Hexacoral-crinoid associations from the modern mesophotic zone: Ecological analogues for Palaeozoic associations [open], Palaeogeography, Palaeoclimatology, Palaeoecology (DOI: 10.1016/j.palaeo.2021.110419)
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