About 375 million years in the past, armored fish dominated an aquatic world. Often called placoderms, these early jawed vertebrates got here in all sizes and styles, from tiny backside dwellers to large filter feeders. Some, just like the wrecking ball-shaped Dunkleosteus, had been among the many ocean's earliest apex predators.
Few of those historic oddities had been stranger than the aptly named Alienacanthus. Found in Poland in 1957, this fish from the Devonian Interval was initially identified for a set of huge bony spines. However the latest discovery of a fossilized alienacanthus cranium, described in a paper printed Wednesday within the journal Royal Society Open Science, reveals that these spines had been truly the elongated decrease jaw of the fish. Measuring twice so long as the remainder of the fish's cranium, this decrease jaw gave alienacanthus nature's most excessive underbite, and maybe a stiff decrease lip.
“It's nonetheless very overseas, so the identify may be very applicable,” stated Melina Jobbins, a paleontologist who research placoderms on the College of Zurich and is an creator on the paper.
Since its discovery within the Fifties, Alienacanthus is understood solely from just a few fossils found within the mountains of central Poland and Morocco. Throughout the Late Devonian Interval, these areas had been submerged coastlines at reverse ends of an unlimited sea that separated the northern and southern supercontinents. However many of those fossils are fragmentary and supply little element about what this unusual fish regarded like.
Over the previous 20 years, researchers have found different well-preserved Alienacanthus fossils in European museum collections. Dr. Jobbins has teamed up with researchers from many of those museums to piece collectively the fossil items and extra precisely describe the traditional fish.
The important thing to cracking this fishy enigma was an almost full alienacanthus cranium over two and a half toes lengthy that originated in Morocco and is at present within the assortment of the Paleontological Institute of the College of Zurich. With the cranium parts nonetheless articulated, the crew realized that Alienacanthus' oddly formed spines had been truly its decrease jaw bones. This made the fish even weirder: when it closed its mouth, the placoderm regarded like a goldfish with an extended backside jaw and beak.
Whereas fish similar to swordfish and noticed sharks have dramatic higher jaw protrusions, only a few species possess elongated decrease jaw protrusions. At present, this characteristic is simply seen in a bunch of small fish referred to as halfbeaks. However the relative size of the decrease jaw of Alienacanthus was 20 % higher than that of the half-beak. The jaw of Alienacanthus was additionally proportionally longer than comparable constructions seen in prehistoric sharks and marsupials, making the fossil fish the undisputed champion of the underbite.
The enlarged jaw could have helped Alienacanthus scoop up sediment, which is how fashionable beaked whales use their shovel-like jaws. One other speculation is that the prehistoric fish used its decrease jaw to stun or injure its prey.
Dr. Jobbins thinks that the elongated jaw, which was studded with curved enamel that prolonged nicely previous the place his higher jaw ended, most certainly served as a lure. “Principally it may ship the prey in after which they will't get out as a result of there's just one solution to go,” he stated. The shorter higher jaw of Alienacanthus may transfer independently of the decrease jaw and shut as soon as a fish or squid was too deep.
This snaggletoothed fish is an intriguingly unusual evolution. As a placoderm, Alienacanthus belonged to the primary teams of vertebrates to develop advanced jaws. The fish offers a glimpse of how excessive jaws might need been simply after the origin of the now widespread characteristic.
Alienacanthus additionally represents one of many final chapters of placoderm evolutionary ingenuity. Inside 15 million years of the looks of the cup-toothed Alienacanthus, these armored fish had been worn out and changed by sharks.
