 Iguanodon were bulky herbivores that could shift from bipedality to quadrupedality . The only well @-@ supported species , I. bernissartensis , is estimated to have weighed about 3 @.@ 08 tonnes ( 3 @.@ 4 tons ) on average , and measured about 10 metres ( 33 feet ) long as an adult , with some specimens possibly as long as 13 metres ( 43 feet ) . These animals had large , tall but narrow skulls , with toothless beaks probably covered with keratin , and teeth like those of iguanas , but much larger and more closely packed . 
 Iguanodon <a href='uninflect' title='1'><mark>were</mark></a> bulky herbivores <a href='null_relcl' title='2'><mark>that</mark></a>could shift from bipedality to quadrupedality . The only well @-@ supported species , I. bernissartensis , is estimated to <a href='been_done' title='3'><mark>have</mark></a> weighed about 3 @.@ 08 tonnes ( 3 @.@ 4 tons ) on average , and measured about 10 metres ( 33 feet ) long as an adult , with some specimens possibly as long as 13 metres ( 43 feet ) . These animals had large , tall but narrow skulls , with toothless beaks probably covered with keratin , and teeth like those of iguanas , but much larger and more closely packed . 
Iguanodon was bulky herbivores could shift from bipedality to quadrupedality . da only well @-@ supported species , I. bernissartensis , is estimated to done weighed abt 3 @.@ 08 tonnes ( 3 @.@ 4 tons ) on average , and measured about 10 metres ( 33 feet ) long as an adult , with sum specimens possibly as long as 13 metres ( 43 feet ) . These animals had large , tall but narrow skulls , w/ toothless beaks def covered with keratin , and teeth like those of iguanas , but much larger and more closely packed .