I have been gardening for many years but have never seen anything like this. About 2 inches long, plump, roughly the same green as the tomato plant, and here is the weird part: covered with white nodes the whole width & length of the top of its body. When disturbed, some of the nodes came off... almost as if it was some sort of defense mechanism, like a porcupine's quills.

Saw only 4 of the worms & there does not seem to be very much damage so far, though 2 tomatoes were punctured and some growing tips of top branches seem to have been nipped off. Did notice that all 4 worms were on the top outside of the plants; based on this one observation they do not seem to live in the darker inside areas.

Thank you if you can identify this creature and for any advice on how to head off further damage.