This is a page from the Giganotosaurus book. This dinosaur was longer and heavier than T. Rex, but probably lacked the brute strength of T. Rex. It was discovered by an amateur paleontologist in Argentina, where the biggest dinosaurs of all have been discovered.
Giganotosaurus had serrated teeth, another difference between it and its more famous counterpart... and actually T. Rex came much later. It's possible that these guys hunted in groups and went after dinos that were several times their size.
They suffered from low self-esteem and were known in paleontological circles as crybabysaurus. Fossil impressions reveal that they experienced pattern baldness and by two years of age had a caeser-like crown of feathers around their small-brained skulls. It's probable that Giganotosaurus was domesticated and used by the Mayans to move massive stones used in building the pyramids, much like the Egyptians used dinosaurs to build their pyramids. Giganotosaurus had ticklish feet.