But based on chimaeras that have washed ashore or been caught as bycatch, researchers know that these fish have cartilaginous skeletons, indicating that the mysterious animals are related to sharks and rays, which also have cartilaginous bodies. Analysis of the brain case of Dwykaselachus oosthuizeni, a shark-like fossil from South Africa, shows telltale structures of the brain, major cranial nerves, nostrils and inner ear belonging to modern-day chimaeras. This discovery, published early online in Nature on Jan. 4, allows scientists to firmly anchor chimaeroids -- the last major surviving vertebrate group to be properly situated on the tree of life -- in evolutionary history, and sheds light on the early development of these fish as they diverged from their deep, shared ancestry with sharks. "Chimaeras are ancient specialists, now anchored within a large and very distinctive group of early shark-like fishes that thrived in the late Paleozoic era," said the study's lead researcher Michael Coates, a professor in the Department of Organismal Biology and Anatomy at the University of Chicago. More than a century later, the relationship between chimaeras, the earliest sharks, and other early jawed fishes in the fossil record continues to puzzle paleontologists. Roy Oosthuizen, an amateur fossil collector, discovered the specimen on his farm in Cape Province, South Africa, in the 1980s, and it had stayed at the South African Museum in Cape Town ever since. In 2013, when the University of the Witwatersrand Evolutionary Studies Institute obtained a micro CT scanner, Dr. Robert Gess, a South African Centre of Excellence in Palaeosciences partner and co-author of this study, began scanning Devonian shark fossils while he was based at the Rhodes University Geology Department. At the surface, Dwykaselachus appeared to be a symmoriid shark, a bizarre group of 300+ million-year-old sharks, known for their unusual dorsal fin spines, some resembling boom-like prongs and others surreal ironing boards. Intriguingly, some of D. oosthuizeni's braincase structures, including its major cranial nerves, nostrils and inner ear resembled those seen in modern chimaeras, the researchers found. Instead of what became modern-day sharks, Coates said, revelations from this study indicate that "much of this new biodiversity was, instead, early chimaeras." The discovery indicates that the evolutionary lineage leading to chimaeras is rooted deeply within this group of early shark-like fishes, of which Dwykaselachus is a late, but anatomically conservative, representative, Coates said.
– The chimaera, or so-called "ghost shark," is an elusive deep-water fish that has fascinated biologists for more than a century. Like its relative the shark, however, it's made of cartilage and thus rarely fossilizes, so little is known about its evolutionary past, reports Live Science. Now the blanks have been filled in thanks to a "remarkable" 280 million-year-old fossil found on a farm in Cape Province, South Africa, in the 1980s that was thought to be a symmoriid shark. Researchers at the University of Chicago Medical Center report in a ScienceDaily news release that the specimen—micro CT scan images of which one reviewer describes as "dripping with data"—is actually an early chimaera, not a shark. The specimen offers "a glimpse of the preconditions from which modern chimaeras evolved." Reporting in the journal Nature, the team says the fossil establishes strong links between the brains, major cranial nerves, nostrils, and inner ears of early and modern chimaeras. We're learning more about elusive modern chimaeras, too: Scientists recently said they think they've captured video of a type of ghost shark never filmed before; the Washington Post published the footage of what's believed to be a pointy-nosed blue chimaera last month. Filmed off the coast of central California, it's the first seen outside the Pacific waters of Australia and New Zealand, suggesting widespread populations. Scientists have yet to work out what chimaeras eat, how often they reproduce, or even how long they live. (Researchers who filmed the ghost shark say it came down to "dumb luck.")