Utahraptor

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Tetanurae > Avetheropoda > Coelurosauria > Maniraptora > Pennaraptora > Paraves > Dromaeosauridae > Eudromaeosauria > Dromaeosaurinae

Overview: In the mid-1970’s, a few scattered fossils of this animal were recovered from a quarry in Utah, including a massive claw. Scientists at the time weren’t sure what to make of the bones, but a few distinctly dromaeosaurid or “raptor-like” traits were noted. However, the remains were of a decently large theropod. Researchers didn’t believe any of the dromaeosaurids obtained such large sizes, but further discoveries in 1991 would prove them mistaken. Within similarly-aged rock layers, some more claws, leg bones, vertebrae, and bits of skull were recovered, which clearly revealed the animal to have been a dromaeosaurid – an enormous one. Based on this material, Utahraptor was officially described in 1993, causing quite the stir. The name, of course, honors the state where its fossils were recovered, within the deeper rock layers of the famous Cedar Mountain Formation. It probably coexisted with a number of dinosaurs. This included therizinosaurs like Falcarius, armored ankylosaurs like Gastonia, sauropods like Cedarosaurus and Moabosaurus, various ornithopods like Iguanacolossus and Hippodraco, and an unknown large-bodied allosauroid theropod.

Excluding the aforementioned allosauroid, Utahraptor was among the largest predators in its local environment. The highest length estimates put it at seven meters long, though some recent studies suggest more conservative estimates of between five and six meters. Either way, Utahraptor was a bulky creature by dromaeosaurid standards, weighing as much as a grizzly bear. Most agree it’s the largest dromaeosaurid yet described, rivaled only by genera like Achillobator. Utahraptor sported a massive claw on each of its second toes, similar to other “raptors”, the bone cores of which could grow to be about twenty-four centimeters (nine inches) long. In life, they sported a keratin sheathe that increased their size beyond this. These curved weapons were used to grip into the flesh of its prey and pierce vital points, or to hold on as it attacked with its jaws. Said jaws were deep, with a notable downward curve at the tip of its lower jaw. Utahraptor is usually classified as a member of the subfamily Dromaeosaurinae, so it was close to Achillobator and Dromaeosaurus. As a derived maniraptoran dinosaur, Utahraptor very likely sported at least limited feathers.