Fossilized slime of ancient eel-like creature shakes up vertebrate family tree

Big Brains Podcast - What ripples in space-time tell us about the universe Paleontologists at the University of Chicago have discovered the first detailed fossil of a hagfish, the slimy, eel-like carrion feeders of the ocean. The 100-million-year-old fossil helps answer questions about when these ancient, jawless fish branched off the evolutionary tree from the lineage that gave rise to modern-day jawed vertebrates, including bony fish and humans. The fossil, named Tethymyxine tapirostrum, is a 12-inch-long fish embedded in a slab of Cretaceous period limestone from Lebanon. It fills a 100-million-year gap in the fossil record and shows that hagfish are more closely related to the blood-sucking lamprey than to other fishes. This means that both hagfish and lampreys evolved their eel-like body shape and strange feeding systems after they branched off from the rest of the vertebrate line of ancestry about 500 million years ago. "This is a major reorganization of the family tree of all fish and their descendants. This allows us to put an evolutionary date on unique traits that set hagfish apart from all other animals," said Tetsuto Miyashita, a Chicago Fellow in the Department of Organismal Biology and Anatomy at UChicago, who led the research.