Complex sentence: On each hand it bore a thumb claw that's much smaller than the thumb claw of Iguanodon and have a very unusual head that resembled a hadrosaur, a duckbilled dinosaur.
Split into simpler sentences: On each hand it bore a thumb claw that was much smaller than the thumb claw of Iguanodon. It had an unusual head that resembled a hadrosaur, a duckbilled dinosaur.