What were the largest species of all time? Does the Tyrannosaurus rex make the list?

Titanoboa was one gigantic snake. It lived around 58 to 60 million years ago, a scant several million years after the mass extinction that wiped out the dinosaurs. It could grow 42 feet or more in length and weigh more than a ton, vastly outslithering the previous fossil record holder, a 40-million-year-old, 33-foot-long snake called Gigantophis. But Titanoboa is just one proud inductee in the Prehistoric Giants Hall of Fame. Meet the other record-holders.

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Largest herbivorous dinosaur

Of all the dinosaur superlatives, “biggest dinosaur ever” is one of the most prized. The trouble is that we don’t really know who deserves the title. Sauropods like Apatosaurus (once known as “Brontosaurus”) and Diplodocus, both at roughly 70 feet long, seemed to be the champions during the 19th century, but since then a variety of even bigger sauropods has been found.

The trouble is that the top contenders have been found only in fragments, so their absolute lengths are a matter of estimation.

At the moment, the largest known dinosaur seems to be Argentinosaurus, a long-necked sauropod that lived 94 million years ago in Argentina. This massive creature is estimated to have stretched 100 feet long and weighed more than 73 tons. Other contenders in the roughly 100-foot range are Supersaurus,Sauroposeidon and Futalognkosaurus. 

But one dinosaur may have been much, much bigger. In 1878, paleontologist Edward Drinker Cope gave the name Amphiocoelias fragillimus to a dinosaur represented by a five-foot-high neural arch, the top bit of a single vertebra. This must have belonged to an enormous dinosaur, but no other bones were ever found and this single specimen mysteriously disappeared more than a century ago. Paleontologist Kenneth Carpenter estimated that Amphiocoelias may have been anywhere from 130 to 200 feet long and weighed over 100 tons. Was this Jurassic giant truly the biggest dinosaur—and biggest animal—of all time? Until someone finds better fossils, we may never know.

And among the theropods, Giganotosaurus from South America and Carcharodontosaurus from the Sahara have given Tyrannosaurus some close competition. Both of these knife-toothed dinosaurs were about 40 to 43 feet long. The competition in this group is currently too close to call.

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(Jon Hughes / Dorling Kindersley)

Largest predatory dinosaur

Tyrannosaurus rex may be the king of the predatory dinosaurs in pop culture, but the 42-foot-long carnivore may not have been the largest. The sail-backed Spinosaurus from the Cretaceous Period might have been the longest of the predatory dinosaurs. Although no complete skeleton has been found, estimates place this bruiser at between 41 and 59 feet long. 

And among the theropods, Giganotosaurus from South America and Carcharodontosaurus from the Sahara have given Tyrannosaurus some close competition. Both of these knife-toothed dinosaurs were about 40 to 43 feet long. The competition in this group is currently too close to call.

Largest flying bird

There have been many big birds in the history of life, from the 10-foot-high flightless elephant birds of Madagascar to the carnivorous, earth-bound, 9-foot-tall Brontornis of prehistoric Patagonia. But the roughly 6-million-year-old Argentavis magnificens was special. With a wingspan of 23 feet, this was the largest flying bird of all time. Exactly how such a large bird took off is a matter of debate, but its anatomy indicates that it was primarily a glider, like modern vultures and condors. Unless there is an even larger fossil bird out there, Argentavis may represent the upper limit for how big birds could get without sacrificing the power of flight.

Largest frog

Today’s largest frog, the 13-inch-long goliath frog, is an imposing amphibian. But the recently described Beelzebufo was even bigger. This frog, discovered in the 70-million-year-old rock of Madagascar, measured about 16 inches long and may have weighed more than 10 pounds.

Largest arthropod

Millions and millions of years ago, the earth was overrun with oversized arthropods, the phylum that includes spiders, scorpions, crabs, centipedes and barnacles. They crawled through the undergrowth, flew through the air and swam in the sea. The biggest of all may have been Jaekelopterus rhenaniae, a fearsome-looking sea scorpion. The 390-million-year-old creature has no modern equivalent; horseshoe crabs are its closest living relatives. 

The creature had been known to paleontologists for decades, but the description of a huge claw in 2007 catapulted the obscure creature to fame. According to paleontologist Simon Braddy and colleagues, the 18-inch long claw indicates that the aquatic predator may have been more than eight feet long.

Largest land mammal

Today’s whales are the biggest mammals that have ever lived. On land, however, mammals hit their top size between 37 and 23 million years ago in the form of Paraceratherium. This huge, hoofed mammal belonged to a group of hornless rhinoceros called hyracodonts, and Paraceratherium itself looked something like a rhino impersonating a giraffe. The herbivore stood about 18 feet high at the shoulder and could have reached its head 25 feet off the ground. Not even the most massive of the mammoths grew quite so large.