Feet seem to have become the order of the day of late as one idea has spread through and I realise there’s more to say on them. On that note, on to perhaps the most famous of feet in the dinosaur world, that of the dromaeosaurs. Yes it’s time to look at the killer claws on Deinonychus (pictured). Actually, it’s a pretty terrible photo that doesn’t show off all of what I want to to talk about but it’s all I got right now (though you can get some more bits here and here).
You can see that the hallux is present and again quite large, which means that the famous ‘raptorial’ claw is therefore on the end of digit 2. This is indeed bigger than those of digits 3 and 4 which help to make it stand out, but it’s the position that it’s capable oh holding that makes it truly interesting. While the claw itself is somewhat specialised, the ‘cocked’ position of the claw is ultimately more down to the specialised phalanx it sits on. That has a rather unusual shape and to a degree, the end connecting with the claw looks almost upside-down.
The joints of finger and toe bones in theropods generally have a little roller joint between the bones (the joint between the phalanx and claw on Linhenkyus shows this really well). But in the specialised one here, that roll can carry on right over the back of the bone to pull the claw right back, and that last phalanx can pull almost the same trick too. That’s what gets the claw cocked in the incredible position (and if you’ve tried bending your fingers back at the joints you’ll know that’s otherwise quite tricky).
This does incidentally appear to be the normal ‘resting’ posture for the toe as shown by footprints of theropods with just two toes showing and a bulge from the base of digit 2. These are dromaeosaur tracks. Well, probably, since actually troodontids pull the same trick so telling one set of tracks from the other is tricky (though people are working on this) but the general point should still hold true of the toe being held in this position while walking around.