Acheroraptor: Beast of the Week

This week let's take a look at a mysterious, yet at the same time, very familiar dinosaur.  Check out Acheroraptor temertyorum!

Acheroraptor was a meat-eating dinosaur that lived during the Late Cretaceus Period, about 66 million years ago in what is now the Montana, USA.  It is estimated to have measured about six feet long from snout to tail, but this is mostly based on the proportions of other related dinosaurs that are more completely known, since Acheroraptor is known from very fragmentary remains.  The genus name translates to "Underworld Thief" in reference to the Hell Creek Formation, the geological formation in Montana, from which its remains, along with those of many other dinosaurs, were unearthed.  When alive, Acheroraptor lived alongside very famous creatures, like Tyrannosaurus, Triceratops, and Ankylosaurus, as well as Quetzalcoatlus, Pachycephalosaurus, Anatotitan, and Anzu.

Acheroraptor life reconstruction by Christopher DiPiazza. (Mostly based off Velociraptor)

Acheroraptor was a member of the dromaeosaurid family.  These predatory dinosaurs were known for being relatively small, feathered, and for having a retractable sickle-shaped claw on each foot.  The most famous member of this group, obviously being Velociraptor.  This family of dinosaurs can be tracked back to the early Cretaceous where they proceeded all the way to the very end of the Mesozoic Era, Acheroraptor, being one of the very last, and was likely one of the species to have died out when the meteorite hit the earth, 66 million years ago.

Acheroraptor has been known about for a long time, in the form of isolated teeth scattered around the Hell Creek formation, but was never given a formal name.  Believe it or not, paleontologists who know their dinosaurs can identify a tooth alone as being from a dromaeosaur!  Dromaeosaur teeth tend to be triangular, blade-like, and have serrations on both sides.  It was simply referred to as "That dromaeosaur from the Hell Creek Formation" for years until some fragments of its actual jaws were finally found and it was formally named and described in 2013.

Known Acheroraptor jaw material from Evans' 2013 paper.

What's interesting about Acheroraptor is that, despite the fact that it lived in North America, by closely examining its teeth and the shape of its jaw, paleontologists were able to deduct that it was most closely related to Asian droameosaurids, like Velociraptor, and not other North American dromaeosaurids like Dromaeosaurus or Deinonychus.  This suggests that Acheroraptor's ancestors migrated to North America from Asia when the continents were connected.  This is also thought to have been the case with its contemporary, Tyrannosaurus, which also had earlier, close relatives from Asia.

That is all for this week!  As always feel free to comment below or on our facebook page!

References

Evans, D. C.; Larson, D. W.; Currie, P. J. (2013). "A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America". Naturwissenschaften.