In them, he hopes, are the fossils that will secure his position as the rising star of American palaeontology. Edward Drinker Cope gets to work on the jumble of bones that were discovered near a lonely fort in remote Kansas. He knows he is dealing with a creature related to large aquatic reptiles that flourished 75 million years ago. Soon he announces that he is in possession of a giant plesiosaur, the most complete ever found in north America. He has called it Elasmosaurus.

The hot-headed 28-year-old is a man in a hurry. In July he tells the academy that the nobbles and bumps on Elasmosaurus’s 12-metre backbone run in the opposite direction to normal. In fact, he says, “the structure of the genus was shown to be entirely new and peculiar among vertebrated animals”.

The following year, in a “pre-print” of his work on extinct reptiles, the professor sends all his mates a drawing of Elasmosaurus. Cope, an expert on lizards, has sketched a creature with a short neck and a very, very long tail. Its odd backbone makes it unique so he creates the order of “reversed lizards”, or “Streptosauria”, to provide it with a home.

Unfortunately, Cope had overlooked one tiny bone. A small and unusual bone that went, he initially assumed, at the tail end of Elasmosaurus. Perhaps he meant to study it later. Perhaps he just forgot about it.

Either way, this was a shame because, as a colleague pointed out to the Philadelphia academy in 1870, it was not an end-of-tail bone, but a start-of-head bone. The brilliant young professor had made a rather silly mistake. Elasmosaurus was in fact a creature with a short tail and a very, very long neck. There was nothing unusual about its backbone.

Cope devoted his life and money to palaeontology. Before he died, surrounded by ancient bones in the academy’s museum, he had discovered and named more than 1,000 fossilised animals. No prizes for guessing which is the most famous.

Stephanie Northen