According to my records, the Dactyl and a "Lightning Flash" NPC graphic share palette 0x81 (129 dec). Hope that's not a problem...
In any case, here's the initial Cedric's Ark graphic insertion patch. The graphics pack compressed quite nicely, with lots of room to spare! I guess I didn't need to be so conservative with the assembly frames after all.
The first frame of the sprite will close the Ark, and the second frame will open it. I'm not sure what your animation needs are, and I'm not sure if the dactyl's current animation data will suffice. If not, just give me a confirmation on whether you need the following:
2 frames total, one open and one closed
Animation 1: Ark closed
Animation 2: Ark open
Each animation should consist of one frame each.
EDIT: Oh snap, just read ZeaLitY's post. I can carve out the Ark's palette, but I need to know where to put it for a new patch.