I keep chickens, free range.  How can anyone who keeps chucks doubt they are descended from therapods?  But that is not the question.  You've seen walking with dinosaurs (etc), yes?  The therapods seem to me be based on cats, when they are feeding and excited, or fighting, they look just like my Spikey, with the tail movements and all that.  But if I go out to feed the birds, and they run after me, they can get a really good wiggle-on with their head bobbing back and forth.  You've seen it with pigeons, too.  SO, how do we know T-Rex or whatever therapod did not move in the same way?  I really want to imagine them heading forward with the bobbbing head.  I guess the media couldn't show such, because it would destroy their whole mystique.  But what is the truth, do we know?  Are there any animations anyone knows of such?  Or am I on the wrong track and there is some actual biological reason to think that head-bobbing is post KT?  Thanks in advance. Steve

It's unlikely that something like T. rex would have bobbed it's head, because that head is so massive, it wouldn't make sense to have to move it back and forth. 

It is feasible that the smaller, more avian theropods could have bobbed their heads when walking though.

The truth is, it's still not certain why some birds do bob their heads when walking.  Most research tends to suggest it's a visual stability thing, but in that case it's very difficult to extrapolate back to whether dinosaurs did this.  The fact that not all birds do it (in fact, a relatively small proportion) means it would be extrapolating a bit too far to say that non-avian theropods did it too.