There are so many claims to which animals are the largest carnivorous and herbivorous dinosaurs that it’s difficult to keep up. The favorite contender for a carnivore is the famous Tyrannosaurus rex, the Cretaceous period carnivore found in North America and Asia. It measured over 40 feet (12 meters) in length. Several other challengers are the Giganotosaurus of South America, and the Carcharodontosaurus of North Africa, two huge meat-eaters. There is also the Spinosaurus, a dinosaur measuring up to 52 to 59 feet (16 to 18 meters) long, which is often declared the largest known carnivorous dinosaur.

Some scientists also give the lead to a certain fossil of a Tyrannosaurus whose huge pubis bone was found in Fort Peck, Montana, in 1997. This creature was so massive that scientists have given the fossil its own name: Tyrannosaurus imperator. This tyrannosaur’s pubis bone measured 52.4 inches (133 centimeters) long; the pubis of Giganotosaurus was only 46.5 inches (118 centimeters) in length, which would make the Montana Tyrannosaurus about 15 to 20 percent larger than any other known meat-eating dinosaur.

The winner of the largest herbivore is even more confusing. One of the best contenders includes a massive herbivorous dinosaur called Argentinosaurus huinculensis, a South American sauropod of the Titanosauridae family that measured between 130 and 140 feet (40 and 42 meters) long. Another contender is the second-largest sauropod so far found, the Paralititan (meaning “tidal Titan”), a titanosaurid sauropod found in Egypt that lived about 100 million years ago. Also, Seismosaurus hallorum, which scientists believe was related to the diploducus, weighed upwards of 100 tons (90 metric tons) and was 120 feet (almost 40 meters) long. A complete skeleton of this huge beast was discovered in 1985 in New Mexico.

No doubt, the hunt for the largest carnivore and herbivore—and dinosaur—will continue. Paleontologists will find new dinosaur bones, and one of them may one day prove to be the largest dinosaur ever known.