Size and Weight:
Deinocheirus is a case study in how much guesswork paleontologists have to do based on limited evidence. All we know for sure about this dinosaur is 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 hasn't kept experts from indulging in a little speculation. It's 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.