What’s the largest animal ever to live on planet Earth? Whether you’re measuring in double decker buses, swimming pools or African elephants, any budding naturalist will be able to tell you that the answer is the blue whale. At 31 metres long and weighing 146 tonnes, this enormous cetacean easily exceeds the paltry dimensions of such pretenders as diplodocus and Tyrannosaurus rex. In London’s Natural History Museum, one of the rare institutions where life-sized models of both animals exist side-by-side, the blue whale has a good three metres on Dippy the beloved Diplodocus.
The blue whale has had to fend off another challenger this week, in the form of Dreadnaughtus schrani, a behemoth from 77 million years ago thought to measure 26m from tip to tip. Dreadnaughtus has made headlines as the most complete sauropod skeleton ever discovered, a body of evidence which provides ample confirmation of its titanic size.
But the absence of such complete remains has never stood in the way of scientists looking to predict an animal’s length and height. The dimensions of the largest dinosaurs have often been extrapolated from just a few fragments of their enormous skeletons. In one notable case, the discovery of a single vertebra led to the prediction of an entirely new species of dinosaur, larger than any that had come before or since. A dinosaur that would make the blue whale look like small fry: Amphicoelias fragillimus.
In 1878, a schoolteacher named Oramel Lucas was excavating a quarry in Colorado on behalf of the great American palaeontologist Edward Drinker Cope. Near the base of a hill now romantically known as Cope’s Nipple, Lucas discovered a single bone coloured a dramatic red by the surrounding mudstone. Despite its enormous size, millennia of erosion had left it thin and highly susceptible to fracture, and it took a tremendous amount of skill to ship it across the country.
Once the bone was in his possession, Cope was quickly able to identify the specimen as a neural arch, the hollow section of a dinosaur vertebra through which the spinal cord would once have passed. Even without the rest of the bone attached the single fragment was 1.5m high, an unprecedented size for a dinosaur. Cope estimated that the full vertebra would have been 2.7m tall, making its owner by far the largest creature of the late Jurassic period.
But just how big was it? With only a single bone to work from, Cope had his work cut out for him. The best he could do was compare it to the vertebrae of the more complete specimens of Diplodocus and Camarasaurus. Treating Amphicoelias as a scaled-up version of these rival sauropods, he reached an estimated length of 58m – which was later revised in 1994 to anywhere between 40 and at most 60 metres. By comparison, Dippy the diplodocus would have been around the length of Amphicoelias’s massive tail.
If Amphicoelias was everything it’s cracked up to be, it would have been by far the largest creature to ever live on Planet Earth. Twice as long as Apatasaurus and five times as heavy, no other known species even comes close to rivalling its dimensions. Even the blue whale, which can be up to 50% heavier, has to throw in the towel when it comes to length.
And it is, paradoxically, this freakish size that is in part to blame for Amphicoelias’s relative obscurity. Carl Sagan once wrote that extraordinary claims require extraordinary evidence, and a single vertebra just doesn’t cut it. By comparison, the recent specimen of Dreadnaughtus was discovered with 70% of its bones intact – over a hundred more than for any previous sauropod.
What’s more, Cope’s 1878 measurements of that single neural arch are now viewed with a certain amount of scepticism. Whether accidental or deliberate, some palaeontologists believe his original notebooks may contain an error, thereby vastly inflating the significance of his claims. It is worth noting that his contemporary critics – including his bitter rival Othniel Marsh – were sufficiently convinced by the discovery never to challenge Cope in public, despite the added gloss it gave to his reputation.
But why trust Cope’s dusty notebooks at all? Why don’t we just dig the original Amphicoelias specimen out of the archives and measure it all over again?
And actually, this bit is pretty amazing.
The reason we don’t just take another look at it is because nobody knows where it is.
We do know that in 1878 Cope gave it to the American Museum of Natural History, and we also know that it was filed away as specimen number AMNH 5777. In addition to this, we know that fossil preservation methods were extremely primitive at the time, and that the Amphicoelias fragilimus vertebra was – well – pretty frigging fragillimus.
Kenneth Carpenter, who has written what must be the definitive account of Cope’s momentous discovery, believes it may have just crumbled away. That means the only known bone of what might have been the largest dinosaur ever to roam the Earth just fell to pieces in a vast Manhattan storage room nearly 150 years ago. It towered over its landscape for untold generations and lasted 140 million years on the barren slopes of Colorado, but life in the big city was just too much for it.
Numerous expeditions have since been made to the area surrounding Cope’s Nipple in the hope of making a similar find, but none has so far yielded any success. Until that changes, Amphicoelias will have to keep swaying its 50-foot neck across the landscape where dinosaurs have always thrived – our imagination.
Gilead Amit is 1.89m tall, which makes him about the size of a Utahraptor, and of a similar fleshy consistency to its lunch. He tweets at @gileadamit