I came across a low-level one of these while exploring near my starting area. It had originally attacked me when I walked over on my Pter to say hello, so I flew off, and died a few minutes later to raptors.
When I came back to retrieve my Pter, he was circling where I'd died and had Therizino Claws in his inventory.
Don't know if it was just a bizarre glitch or Pters are his supervillain weakness (and I won't know soon... I'm catching the next one I find, dagnabit!)