Way back in the 1800s (well probably not so back, at least we are taking in difference of hundreds of years here, not millions of years), this elephant sized plant eater was one of the first dinosaurs to be found, when scientists had no idea about dinos that were bigger than elephants.
In 1822, the English geologist Gideon Mantel found some fossil teeth that seemed to belong to a giant lizard (in fact it more seemed like a oversized Iguana 😂, which is how this dino also got its name as well). 3 years later, it was officially named Iguanodon (trivia: one of the first dinosaurs to be named).
Iguanodons used to get eaten by predators like the Baryonyx, Yutryannus and Utahraptor. And what could the poor creature do really, the only defence mechanism it had was it’s thumb nail, that was as sharp as a steak knife but possibly was still insufficient to defend itself from it’s predators because