Tunicates, strange tube-like creatures in various colors, shapes and sizes, are found on ship hulls, larger seashells, pier pilings, seafloors and the backs of enormous crabs in oceans worldwide. Their basic shape is a short, barrel-like sack with two siphons or openings that filter feed water from one siphon for plankton before shooting it back through the other. About 3,000 species of tunicates worldwide reside in saltwater habitats. Despite this, there were no solid records of them in rock deposits for their entire evolutionary history — until now.
Paleontologists uncovered an ancient ancestor to modern-day tunicates for the first time in a recent study published in Nature Communications. The 500-million-year-old fossil is the first of its kind and is exceptionally preserved. Dubbed, Megasiphon thylakos, the specimen, about the size of a thumbprint, sports two siphons and strikingly resembles modern-day ascidiaceans, a tunicate lineage.
“Megasiphon’s morphology suggests to us that the ancestral lifestyle of tunicates involved a non-moving adult that filter fed with its large siphons,” says Karma Nanglu, study author and paleobiologist at Harvard University, in a statement. “It’s so rare to find not just a tunicate fossil, but one that provides a unique and unparalleled view into the early evolutionary origins of this enigmatic group.”
