During the Devonian era, mysterious sharks with bizarre teeth and sinuous bodies swam the seas. Until now, we’ve only known about them from teeth and fin spines, but researchers have finally uncovered skeletal remains in Morocco, shedding light on what these strange toothy fishes were like.
Describing their finds in the Proceedings of the Royal Society B, the researchers uncovered near-complete skeletal remains, including several skulls, from two different species belonging to the genus Phoebodus. Shark skeletons are notoriously tricky to stumble upon because they are made out of cartilage, not bone.
"It is hard to find shark skeletons of this completeness and quality because they are made out of cartilage," first author Linda Frey, of the Palaeontologocial Institute and Museum at the University of Zurich, told IFLScience. "Cartilage is not that robust such as bone and therefore, it is less often preserved. For this reason, we were overwhelmed by making such a discovery.
"Although the shark Phoebodus was known from plenty of teeth material for decades, skeletons were completely absent before our recent discoveries." Cartilaginous fish are known as Chondrichthyes and include sharks, skates, and rays.
The new remains were found in the Maïder region of Morocco, an area known for its Drotops trilobite fossils. Once a shallow sea, the sharks lived there during the Late Devonian, a period spanning 376 to 360 million years ago that preceded the Carboniferous period. Poor water circulation would have helped to preserve the sharks’ bodies by creating a low-oxygen environment.
One of the most notable features of this group of sharks hinted at by the remains is that they had anguilliform – or eel-like – bodies, in addition to a long jaw and nose. The physical characteristics of the genus suggest it is closely related to a species of elasmobranch called Thrinacodus gracia, discovered in limestone in Montana, that lived during the Carboniferous era.
The researchers note that Phoebodus is reminiscent of another shark, but less in terms of relatedness and more in terms of looks. The frilled shark (Chlamydoselachus anguineus) is a living species of shark found in both the Atlantic and Pacific Oceans. A strange creature, it has an eel-like body and slightly horror-film-esque teeth arranged in neatly separated rows, each with three sharp spikes.
The bizarre frilled shark.
Well-known sharks like the great white chomp up their prey, but frilled sharks use a different approach. Their unique sets of teeth allow them to grab onto prey and then swallow it whole, with inward-pointing gnashers preventing any unlucky fish that finds its way into the shark’s mouth from escaping.
CT scans of the new fossils suggest that Phoebodus may have fed in a similar way to frilled sharks as both their teeth and body shapes are remarkably similar. The team also thinks that Phoebodus’ feeding technique may share similarities with that of the alligator gar (Atractosteus spatula), one of the biggest freshwater fishes in North America, which has a long, flat, almost crocodilian snout that helps it grab fish that appear at its side.
New finds might tell us more about the physiology and behavior of ancient Phoebodus sharks, but for now, we have the most complete skeleton of one of these marine beasts ever uncovered, and that’s pretty awesome.