Deinocheirus (Greek for "terrible hand"); pronounced die-no-CARE-us
Deserts of Asia
Late Cretaceous (70 million years ago)
Size and Weight:
About 36 feet long and one or two tons
Long arms with three long fingers on each hand
Deinocheirus is a case study in how much guesswork paleontologists have to do based on limited evidence. Until recently, all we knew for sure about this dinosaur had been based on a handful of fossil remains--specifically, two long forelimbs and bits of ribs and vertebrae--that were dug up in southern Mongolia in 1970. Still, this didn't keep experts from indulging in a little speculation. It was surmised that Deinocheirus had a bipedal stance, and used its long, clawed arms to hunt down and eat smaller prey (although some paleontologists think this dinosaur may have used its long fingers to climb trees--and thus may have had a herbivorous diet, like modern sloths). The current consensus is that Deinocheirus was an ornithomimid ("bird mimic"), which would make it one of the few ornithomimids whose name doesn't end in "-mimus".
Recently, a team of paleontologists studying the "type fossil" of Deinocheirus came to a startling conclusion: the reason so little was left of this dinosaur is that it had just been eaten by a larger predator, probably a tyrannosaur like Tarbosaurus. Since it seems unlikely that even the fastest theropod could have outrun an ornithomimid, this particular Deinocheirus individual was probably scavenged shortly after it died, rather than being actively hunted down and killed.
Even more recently, scientists have announced the discovery of additional Deinocheirus fossils, allowing them to recreate this dinosaur in its entirety. It seems that Deinocheirus was indeed an ornithomimid, albeit one that looked uncannily like a therizinosaur, and it may have had a small hump on its back, function unknown. According to the new estimates, Deinocheirus measured a whopping 36 feet from head to tail and towered 16 feet above the ground, which would make it by far the largest "bird mimic" dinosaur yet identified!