08 July 2011
I say behemoth with the utmost respect, not only considering that this animal could swallow me whole, but also because it was in fact, enormous. In known species Giganotosaurus is rivaled in size by Spinosaurus above and Tyrannosaurus very slightly below, making it quite a huge theropod. The "Giant Southern Lizard" is estimated by bone length to be between 40 and 43 feet long with rather large weight estimates at higher and lower ranges between 6.5 and 13.3 tons. That's much more than just full belly versus empty belly, unless this monster could shove nearly seven tons of food down its gullet in one sitting.
Probably not impossible for an animal with a skull almost six and a half feet long, but that would be about the equivalent of eating the entire carcass of Sue (the famous T. Rex in Chicago's Field Museum) in one sitting, which we are pretty confident wouldn't have happened with any carnivore at that time. It's just an enormous chunk of flesh to gulp down!
So what did Giganotosaurus eat then? An enlarged olfactory region in the skull and brain point to a keen sense of smell and pack behavior has been theorized, as with many other theropods, for this animal as it hunted the Late Cretaceous of South America. That land at that time was filled with dinosaurs of rather large sizes such as Andesaurus, Argentinosaurus, Adamantisaurus, Rinconsaurus, and Saltasaurus. There have not been many non-sauropod discoveries in South America at this time, and as such, it is difficult to pinpoint any smaller prey of Giganotosaurus, which may certainly account for its overall size as an adult animal.