The scientist Joseph Banks recorded the sighting of an animal "as large as a greyhound, of a mouse colour and very swift". The artist Sydney Parkinson captured it in a sketch.
Now that delicate line drawing of the creature which revolutionised scientific thinking on mammals is to be revealed to the public for the first time next weekend. The Natural History Museum in London is opening an exhibition of the scientific and botanic treasures brought back from voyages by British explorers, many of them never seen in public before.
Illustrating the quest for scientific knowledge, "Voyages of Discovery" shows how many of the finds challenged European preconceptions. The discovery in Australia of the kangaroo, a mammal that gestates in a pouch and not inside the body, and the platypus, a mammal that lays eggs, threw 18th- century thinking into confusion. Paul Bowers, the exhibition researcher, said: "They suddenly started questioning the whole basis of their classification."
The kangaroo was first sighted in 1770, after the Endeavour, the ship of the explorer Captain Cook, hit a reef and those on board were forced to spend six weeks in Queensland. The mishap was a godsend for the young and wealthy naturalist Joseph Banks, who had paid pounds 20,000 to fund a full scientific mission on board a voyage which was principally intended to identify new trading routes and sources of raw materials.
Sydney Parkinson, his young artist, made 680 sketches and 280 finished drawings of plants and wildlife, all now in the Natural History Museum, and noted local words, including "kangaroo". Banks recorded their finds in his journal.
On 22 June 1770 crew members, sent ashore to shoot pigeons, had reported seeing a "greyhound-like" creature the colour of a mouse. Three days later, Banks wrote: "In gathering plants today, I myself had the good fortune to see the beast so much talkd of, tho but imperfectly; he was only like a greyhound in size and running but had a long tail, as long as any greyhounds; what to liken him to I could not tell, nothing certainly that I have seen at all resembles him."
Paul Bowers said: "Although you can recognise the drawing is a kangaroo it is not very accurate. He's trying as an artist to make sense of the beast. Something like a kangaroo is an extremely weird creature if you're used to European wildlife."
However, Parkinson's other drawings, backed by specimens also now held at the Natural History Museum, were detailed and accurate depictions of the flora and fauna. The success of the Endeavour exploration established the principle of having a scientific team on board subsequent voyages. "It engendered the idea that collecting would be an important thing for Britain to do," Mr Bowers said.
Parkinson's drawing of a kangaroo will go on display next weekend beside the first edition of Darwin's Origin of Species and specimens from the Galapagos Islands, the Jamaican chocolate bean from which the 17th-century physician Sir Hans Sloane created milk chocolate, and some of the earliest photographs of icebergs.
A major feature of the exhibition will be a number of the museum's collection of 500,000 drawings and paintings, the third largest in the country. Paul Bowers said: "We have a perception that art is for beauty, but in natural history, the art is part of the science."