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Museum digitises Darwin’s lost Megatherium specimen to mark the 159th anniversary of the publication of On the Origin of Species

Museum scientists have re-discovered and digitised a fragment of one of Charles Darwin’s Megatherium fossils.

Unaccounted for since 1845, the team have digitally re-united it with its corresponding piece, piecing back together this part of the sloth’s cranium for the first time since Darwin discovered it on a beach in Argentina in September 1832.

The Megatherium was a giant ground sloth native to South America. Growing to the size of an elephant, they were some of the largest land animals roaming the landscape when they lived until some 10,000 years ago.

The data will be released to the public via the Museum’s Data Portal on Friday 23 November to commemorate the 159th anniversary of the publication of On the Origin of Species, first published on 24 November 1859. Models will also be released onto the 3D platform

As part of a wider project digitising Darwin’s entire collection of fossil mammals, scientists at the Museum set about researching the Megatherium specimens, important discoveries for the young naturalist. Today, the Museum holds three specimens of Megatherium. The final piece of this collection was a specimen that was in two parts. One fragment is held by the Royal College of Surgeons (RCS) and the other resides at Down House, the home of Darwin.

By studying the journals of Darwin’s voyage to Argentina in the nineteenth century, the Museum’s Dr Pip Brewer and Prof Adrian Lister were able to match Darwin’s descriptions of the giant ground sloth fossils he was uncovering, to the specimens today held by the Museum and the RCS.

However, the Megatherium skull caused some confusion as it had been cut in half; dividing the specimen into two fragments and revealing a cross-section of the teeth. Upon further research, Dr Brewer and Prof Lister found there was no knowledge of the whereabouts of the smaller part of the fossil past 1845.

Having searched the Museum’s huge collection of fossil mammals for the missing fragment, and that of the RCS to no avail, curator of fossil mammals Pip Brewer and palaeobiologist Adrian Lister extended their search to Down House, the home of Charles Darwin, where they were miraculously able to locate the remaining fragment of Darwin’s Megatherium specimen.

When Darwin discovered this fossil in Argentina and sent it to the RCS, he speculated that it was  a skull of Megatherium, but the specimen was surrounded by a matrix meaning it would have been difficult to confirm what creature it was without a fresh cut to reveal more detail. In this case Richard Owen, the first Director of the Natural History Museum, cut this specimen in two in order to better understand its origin, identity and biology. From here, the larger part of the fossil remained in the collection at the RCS, and the smaller section made its way to Down House where they would respectively remain for many years.  

On September 4 2018, both parts of the specimen were brought to the Museum where 3D specialist Kate Burton scanned both fragments using a 3D surface scanner. This scan is the first time that these fragments of the same Megatherium skull have been united in over 150 years. By scanning both fragments of the specimen, the Museum is able to make these vitally important specimens accessible to all, from scientists and educational groups to artists and enthusiasts across the globe, inspiring the next generation of natural world ambassadors.

Curator of fossil mammals Dr Pip Brewer says, “It is absolutely fantastic to see all of the existing Darwin Megatherium specimens reunited again, and scans and details of them freely available worldwide.”

Palaeobiologist Prof Adrian Lister says, ‘Finding the missing piece of Darwins’ Megatherium was an unforgettable moment for me, and now making the virtual skull available to all is a brilliant way of sharing the discovery.’

As well as the two pieces of the large skull, fragments of two other Megatherium specimens were scanned and processed by the Museum’s Digital Collections team. The data will be published via the Museum’s Data Portal on Friday 23 November.

The Digital Collections Programme was initiated at the Museum in 2014 to digitise and make accessible scientific data from its Collection of over 80 million items on an industrial scale. The Museum’s Collection includes over 35 million insects, 5 million plants and more than 320,000 mammals that hold critical information necessary to tackle the scientific challenges of our time - from conserving the biodiversity on which our wellbeing and our planet’s health depend, to finding new ways of combating disease. Further information about this project can be found at


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  • Darwin's Fossils: Discoveries that shaped the theory of evolution (£14.99, PB)
    Adrian Lister’s account of Darwin’s remarkable fossil-hunting adventures in the 1830s, the pioneering science behind the fossils he found, and how these remarkable discoveries played a crucial role in forging his theory of evolution through natural selection.