Stygimoloch spinifer
Named in 1983 by paleontologists Peter Galton and Hans Dieter Sues after the river Styx and the mythological demon known as Moloch, Stygimoloch was a dome-headed dinosaur, or pachycephalosaur, that had an almost flattened dome skull up to 18 inches long, three to four large sharp spikes at the back (the largest up to 6 inches long and 2 inches in diameter) that made it demonic hence its name, and bumps at the front. It was a small dinosaur that was estimated to be up to around 10 feet in length and weighed up to 170 lb., although this animal could've been even larger since the only specimens of Stygimoloch were not yet fully-grown
Living alongside Tyrannosaurus rex, Triceratops prorsus, Ankylosaurus, Edmontosaurus, and Dakotaraptor in what is now the Montana badlands (Hell Creek Formation), as well as Wyoming, during the last days of the age of dinosaurs some 66.8 to 66 million years ago (Latest Maastrichtian stage of the Late Cretaceous period), Stygimoloch was one of the last of the non-avian dinosaurs that ever lived before the K-Pg (Cretaceous-Paleogene) Mass Extinction event.
It probably tried to outrun most larger predators such as Tyrannosaurus rex while it may have fight smaller ones such as Pectinodon and Accheroraptor off with its heavily armored head. Its likely that this dinosaur used its head most often to fight others of its own kind over food, territory and mates, although how dinosaurs like these fought with thier heads is still uncertain as a head to head collision would be fatal. Perhaps Stygimoloch rammed at each-others flanks until one animal backed down or even used its spike-like horns to lock at each other, similar to modern deer.
However, in recent years, its believed by most paleontologists (such as Jack Horner) and experts from a study showing that, as the only specimens of this dinosaur was not yet fully-grown, this animal, along with the flat-headed, dragon-like contemporary relative, Dracorex hogwartsia (who's specific name honors the school from the Harry Potter series), are considered juvenile and adolescent Pachycephalosaurus and represent the growth stages of it from flat-headed to rounded dome-headed, with Stygimoloch being placed in between. If so, then this dinosaur (and Dracorex) is no longer considered valid and is just a teenage Pachycephalosaurus. However, not all experts and scientists agree with this theory and a very recent study and analysis show that Stygimoloch was geologically younger than Pachycephalosaurus, albiet slightly, as it was found in the upper strata of the Hell Creek Formation that dated back at the very end of the Cretaceous period (Latest Maastrichtian), whereas Pachycephalosaurus was found in the lower strata.
Another theory is that its believed that Stygimoloch, along with other pachycephalosaurs, with its shearing sharp teeth, was omnivorous, feeding on plants, seeds, fruits, insects, small animals, and possibly even carrion, but this remains controversial.
