Paramegahadrinae is an extinct group of
North American hadrosaurs that appeared in the middle Oligocene. They were
first thought to have been the ancestors of megahadrines, but certain details
of their anatomy, most importantly the shape of the head and the shortness
of the forelimbs have lead paleontologists to believe they were actually
a primitive evolutionary offshoot of Hadrosauroidae. It seems that while
megahadrines eventually became grazers of the prairies, paramegahadrines
remained in the marshlands and riversides where their common ancestors
had evolved. It is still unclear what events exactly lead into their demise.
Megabeluasaurus was the largest paramegahadrine
species, even though it never surpassed the elephantine hmungos in size.
The first Megabeluasaurus remains found consisted of a nearly intact
skull but very little postcranial material. Based on the enormous size
of the skull, the animal was first reconstructed as an enormous hmungo-like
grazer. Later finds revealed that the skull of Megabeluasaurus was
actually very large in proportion to the rest of its body. The dinosaur
seems to have been a dweller of the wetlands whose diet consisted mostly
of aquatic plants very much like its cousin, the modern sludger.
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