An artist’s reconstruction of the new shark-like species Cosmoselachus mehlingi.
Fossils are not just merely bones, preserved in layers of sediment waiting to be discovered. They are conduits that illuminate the hidden chapters of our planet’s evolutionary tale - and one such chapter has been uncovered in the depths of Arkansas! Hidden within the fossil-rich Fayetteville Shale formation, a species of shark-like creature has finally emerged for the first time.
Meet Cosmoselachus mehlingi, a creature who roamed our seas some 326 million years ago, but was collected from the Fayetteville Shale formation about 45 years ago. Discovered during the 1970s by Royal and Gene Mapes, a married couple who served as esteemed scientists and professors at Ohio University, the fossil found its way to the American Natural History Museum in 2013 along with the rest of their collection as a generous donation. Named in honor of Carl Mehling, a revered figure in the Museum’s Paleontology Division and the world of vertebrate paleontology, as scientist Allison Bronson, aptly puts it: “We are delighted to honor him with a weird old dead fish!” What sets Cosmoselachus apart from its ancient counterparts is not just its nomenclature, but its intricate anatomy.
An anatomy that was meticulously reconstructed by a team of researchers led by Bronson, author of the study detailing Cosmoselachus who is now a researcher at Cal Poly Humboldt. The task was handled by scientists worldwide, with collaborators hailing from the American Museum of Natural History, the University of Florida, and the Museum National d’Histoire Naturelle in France. Through painstaking efforts, including the use of cutting-edge CT-scanning technology, the team pieced together the long-lost features of this ancient animal, shedding light on its place within the evolutionary line of cartilaginous fishes.
Cosmoselachus mehlingi, photographed in the late 1970s, positioned to show the underside of the ... [+]
To simply put it, this animal defies easy categorization.
With its predominantly shark-like traits juxtaposed with peculiar long pieces of cartilage forming a gill cover reminiscent of modern ratfish, Cosmoselachus challenges our preconceived idea of what ancient marine life looked like. “Once the reconstruction was complete, the researchers placed the specimen in the tree of life of early cartilaginous fishes, finding that it plays an important role in understanding the evolution of an enigmatic group called the symmoriiforms,” explained AMNH in a press release. “This group has alternately been linked with sharks and ratfish, with different researchers coming to different conclusions.”
Its existence hints at a time of unparalleled morphological experimentation among cartilaginous fishes — a time of strange anatomical deviations and evolutionary just going wild. For researchers like Bronson and her colleagues, fossils like these serve as portals to the past, allowing them to piece together what an ancient ocean looked like.
Stretching its geological fingers from the heart of southeastern Oklahoma to the rugged terrain of northwestern Arkansas, the expansive Fayetteville Shale formation serves as a time capsule, preserving not only the fossilized remains of ancient sharks but also a variety of invertebrates and plant life. For centuries, scientists and paleontologists have been drawn to this location; its unique composition, coupled with optimal preservation conditions, has yielded an extraordinary bounty of fossils that offer invaluable insights into Earth’s distant past. A researcher is certainly not bored here! “These creatures are part of a recovered ecosystem following a major extinction of fish groups at the end of the Devonian Period,” Bronson concludes. “So it’s a time of incredible morphological diversity in cartilaginous fishes, including all kinds of weird anatomy we don’t see in modern sharks.”
