Therizinosaur belongs to the class of dinosaurs known as Theropods, which is the group made up of bipedal bird-like dinosaurs such as the T-Rex and Raptors. Obviously, this guys two most defining characteristics are his huge claws (although he still has the trademark Theropod short arms lol) and long neck. The reason for these giant 2 foot long talons were not to attack prey like you would expect, but instead to help trim leaves off of trees. Yes, this is an herbivorous Theropod. This makes him have more in common with a Giant Ground Sloth than most of the Raptors.
These guys were around in the late Cretaceous period (100 million to 65 million years ago) along most of the other Theropods. Skeletons have been found mostly in Mongolia, China, and in the Western United States. The discovery of this dinosaur has been pretty recent. The first one was found in Mongolia shortly after World War 2 and paleontologist basically had no idea what the fuck it was. It looks like a Therapod, but it has these huge claws, an herbivorous dentition, and feet similar to Sauropods (think Brontosaurus/Apatosaurus). They didn't get their official classification until the mid 1990s, once more species of this type had been found. Lets be honest here, Therizinosaurs are sort of a mess. The fact that they've baffled scientist for so long means that there isn't a lot of information available about them. But, this is the precise thing that makes them awesome, and thus our first Dinosaur of the Month.