Hell Creek Formation
"Acheroraptor" is the youngest species of dromaeosaurid, and is from the Hell Creek Formation. The Hell Creek Formation is from the time of the Cretaceous-Paleogene Extinction Event, and has been dated to 66 ± 0.07 million years ago. Many animals and plants have been found in the Hell Creek Formation, the discovery site of "Acheroraptor". As it is known from the "Tyrannosaurus"-"Triceratops" fauna, "Acheroraptor" is the youngest dromaeosaurid, along with the much larger "Dakotaraptor".