Following hot on the heels – or is that fins? – of the filter-feeder Aegirocassis– Yawunik kootenayi is the latest ancient invertebrate to make us ask “What the heck is that thing?” Described by paleontologists Cédric Aria, Jean-Bernard Caron, and Robert Gaines from 42 fossils found in Canada’s Kootenay National Park, the Cambrian critter adds to the wonderful and perplexing spread of body plans that had evolved by this chapter in Earth’s history – jutting out from beneath the invertebrate’s tough exoskeletal hood are paired, pinching appendages arrayed with long wisps. The overall effect is of a lobster tail that’s out for revenge on those who drew butter against it.
At the time that Yawunik swam around delivering deadly pinches to worms and other small prey, though, there weren’t lobsters yet. Aria, Caron, and Gaines propose that Yawunik belonged to a lineage of invertebrates called leanchoiliids – a group so obscure they don’t even have a Wikipedia page summarizing what they are – that fit near the base of the arthropod family tree. This doesn’t mean that Yawunik was an ancestor to today’s insects, crustaceans, and arachnids, but rather that it was part of an evolutionary explosion from which the true arthropod ancestors emerged.
Read full original article: Scientists Uncover Yet Another Cambrian Weirdo