Extinct herbivore with thumb spikes (9)

I believe the answer is:

iguanodon

(Other definitions for iguanodon that I've seen before include "In the past a massive herbivore" , "reptile now extinct" , "It used to eat plants" , "Herbivorous dinosaur" , "Long-tailed bipedal dinosaur" .)

I've seen this clue in the Universal.

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