Another troodontid question. Many older restorations of troodontids I have seen (notably the slick-skinned Troodon model often seen paired with the anthropocentrically-conceived "dinosauroid") show it as having an opposable thumb-like digit. Is there any evidence that troodontids actually had this? Could they grasp with their hands at all? (I've heard that deinonychosaur hands would have been incapable of grasping and turning a doorknob as the Velociraptor did in Jurassic Park, but then again those were dromaeosaurs, not troodontids.)

Well Bryan, I have looked over some descriptions of troodontids (as I mentioned before they are actually really quite rare) including some drawings, photos and of course what has actually been written about them, and I can find nothing about an even vaguely opposable 'thumb'. So nope, nothing doing in short - they look just like those of other theropods including their close relatives the dromaeosaurs.

Just as an aside, while they might not have an opposable digit, I do think that the 'Velociraptors' of Jurassic Park could have opened traditional lever door handles. After all, all they have to do is push down on them and then push the door. I know dogs and cats that can manage it, so why not a dinosaur? Even if some grasping was necessary, they may not have an opposable thumb, but can still grasp with the other fingers against the palm wihc should be enough. It would be awkward, but by no means impossible.

Articulated troodontid hands (e.g., those of _Sinornithoides_) don't show an opposable thumb, but Dale Russell specifically argued for one in the 1960s and 80s based on the hand anatomy of _Troodon_ (then known as _Stenonychosaurus_): in a 1981 paper he wrote that 'the structure of the carpal block suggests that the third finger could possibly have been opposed to the other two'. This is why some restoration of troodontids depict the animals with opposable digits. More recent work on the ranges of motion possible in theropod hands (that by Alan Gishlick and Phil Senter) has shown that the three fingers of most theropod hands generally work as a single grasping unit: opposability was present in some maniraptorans (most notably _Bambiraptor_), but the opposability occurs between digits III and I, with digit III being the flexible one.