Simplify the following text for a Grade 9 native English-speaking person.
Original: It includes some of the heaviest creatures ever to walk the earth , such as Argentinosaurus and Paralititan -- which might have weighed up to 100 tonnes ( 110 short tons ) or , perhaps , even double that , if some poorly-described data are to be believed ( see Bruhathkayosaurus ) .
Simplified: The largest might have weighed up to 100 tonnes ( 110 short tons ) or , perhaps , even double that , if some poorly-described data are to be believed ( see Bruhathkayosaurus ) .