Aargh. I know there are papers for the things I’m about to say but I cannot for the life of me dig them up or find them on Google (Scholar is severely lacking…). Anyway, the fact that crocs are aquatic is one reason cited by dino-lip advocates. They point out that all terrestrial reptiles have lip-like structures covering their teeth, and that by extension the lack of lips in crocs must be an aquatic adaptation, though I can’t remember if there are any particular things this adaptation is meant to accomplish, or why lips are better than no lips in terrestrial reptiles.
For what it’s worth, the “lip-pits” Bakker and others talk about for theropods (which, also for what its worth, may have analogues in lipless crocs), might alternately imply the presence of a beak (!).
As for hopping, this idea has kicked around ever since it was discovered that some dinosaurs were bipedal (early skeletal mounts of hadrosaurids and other iguanodonts are famoulsy set in kangaroo-like poses, which required numerous bones to be disarticulated, especially in the tail). A recent paper tested this idea in theropods, finding that the hip structure and muscle attatchments did not resemble modern hopping animals at all and were not suited anatomically for hopping locomotion. Additionally, all hopping animals have very long tarsal (foot) bones compared to their upper legs, while dinosaurs have unusually short feet.
Paradoxically, I remember reports of (small) theropod footprints that suggest hopping. So, there might be more to it.