'' Not showing as much spine - but keeping a very stiff lower lip '' : Some 375 million years ago, armored fishes ruled a watery world.

Known as placoderms, these jawed vertebrates came in all shapes and sizes, from small button-dwellers to giant filter-feeders. Some, like the wrecking-ball - shaped Dunkleosteus, were among the earliest apex predators.

Few of these ancient oddities were more weird than the aptly named Alienacanthus. Discovered in Poland in 1957, the Devonian Period fish was initially known for a set of langy, bony spines.

But the recent discovery of a fossilized Alienacabthus skull, described in a paper published in the journal Royal Society Open Science, shows that these spines were actually the fish's elongated lower jaw.

Measuring twice as long as the rest of the fish's skull, this lower jaw gave Alien Acanthus nature's most extreme underbite.

'' It's still very alien looking, so the name is very fitting,'' daid Melina Jobbins, a paleontologist at the University of Zurich and the author of the paper.

Alienacanthus is known only from a few fossils discovered in the mountains of Central Poland and Morocco

During the late Devonian Period, these areas were submerged off the coasts at opposite ends of an enormous sea that separated northern and southern supercontinents.

The extended jaw may have helped Alienacanthus sift through sediment, which is the way modern halfbeaks utilize their shovel-like jaws.

Another hypothesis is that the prehistoric fish wielded its lower jaw to stun or injure prey.

Alienacanthus also represents one of the final chapters of placoderm evolutionary ingenuity. Within 15 million years of the appearance of Alienacanthus's toothy mug, these armored fish were wiped out and replaced by sharks. [ Jack Tamisiea ]. 


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