LONDON.- We now have a better idea of what one of the most important historical fossils looked like, more than 80 years after the original was lost.

Decades before dinosaurs were formally described, fossils of ancient marine reptiles known as ichthyosaurs were already capturing the public's imagination. In 1819, the first complete specimen, described as Proteosaurus but now known as Ichthyosaurus, was introduced to the world by Sir Everard Home.

This fossil, likely to have been collected by pioneering palaeontologist Mary Anning, was subsequently placed in the collection of the Royal College of Surgeons. It remained here for over a century until, in the closing days of the London Blitz, the college was struck by bombs and the specimen destroyed.

A new paper, published in Royal Society Open Science, reveals that not all was lost. It documents two previously unknown casts of the specimen still exist, making an important fossil available to study once more.

Dr Dean Lomax, a specialist in ancient marine reptiles who led the rediscovery efforts, says, 'Before the fame of the dinosaurs, ichthyosaurs were 'the' famous prehistoric reptiles. Their big skulls, eyes and teeth captured the public's imagination, making the ichthyosaurs icons of evolution.'

'This, and other early ichthyosaur finds, sparked a major interest in collecting more of these curious, enigmatic creatures, and played an important role in establishing palaeontology as a scientific discipline.'

Fossils destroyed in wartime
The destruction of historic and cultural artefacts has long been used as a weapon of war, and the destruction of fossils is no different. During World War One and Two in particular, many important specimens are known to have been destroyed.

Some fossils were destroyed while in transit as a result of military action. For instance, a cache of dinosaur remains destined for the Museum were sunk aboard the SS Mount Temple in 1916 when the ship was attacked by a raiding vessel.

Many more, however, were destroyed by bombing campaigns, with almost the entirety of known Aegyptosaurus fossils, as well as the type specimens of well-known dinosaurs such as Spinosaurus aegyptiacus and Carcharodontosaurus, destroyed during World War Two.

Beyond dinosaurs, other ancient reptiles have also been destroyed. The bombing of Bristol Museum and Art Gallery in 1940 led to the loss of thousands of natural history specimens, including a number of ichthyosaur and plesiosaur types.

While the destruction of fossils is not the most important casualty of war, it still represents the loss of valuable scientific data about how life on Earth evolved and diversified. While the status of some type specimens can be reallocated to later finds, others represent the only example of their species ever discovered.

Recovering copies of now-destroyed specimens ensure that at least some of this knowledge isn't lost forever.

'Casts can be overlooked when it comes to research, but they offer valuable information on the dimensions of fossils,' Dean says. 'The measurements of individual bones and skeletons in casts can be compared to other fossils and can be detailed enough to allow new genera to be named.'

How were the Ichthyosaurus casts rediscovered?
Following the bombing of the Royal College of Surgeons, it was thought that this Ichthyosaurus specimen was lost to history.

But 75 years on, Dean and his co-author Professor Judy Massare were conducting research in the Yale Peabody Museum in Connecticut, USA, in 2016 when they came across a specimen believed to be a real ichthyosaur fossil.

However, the scientists recognised it not as a real fossil but as a cast of Home's original specimen which had been painted to look like a fossil. Three years later, Dean would discover another cast in the collections of the Museum für Naturkunde in Berlin, Germany, whose origins were also unappreciated.

Dr Daniela Schwarz, who is in charge of the fossil reptile collection at the Museum für Naturkunde, says, 'I was really stunned that a cast of this important specimen had rested in our collection for more than a century.'

'This discovery demonstrates the necessity to carefully preserve undetermined and casted material in a natural history collection, because there will always be someone who discovers its scientific value in the end.'

The Peabody cast is believed to be the older of the pair and is less detailed and more worn than the one in Berlin. While both differ from the original illustration, the Berlin specimen is thought to have benefitted from more advanced casting techniques that preserve the original fossil in better detail.

'Until now, the drawing by William Clift was the only visual evidence we had of the ichthyosaur,' Judy says. 'Now, having two casts, we can verify its reliability.'

'We have identified a couple of bones that Home missed and found a few discrepancies between the drawing and the casts.'

The researchers hope that the rediscovery of the casts could prompt a re-examination of collections around the world, and perhaps discover more specimens thought lost to time.

'I suspect that several more Proteosaurus casts will come to light,' Dean says. 'It's intriguing that we haven't found a cast yet in the UK, given its importance to British palaeontology, so I suspect one or two may come from an institution here.'

'I hope that this paper will inspire curators and other researchers to take a fresh look at casts held in collections, as there may be incredibly important specimens lost to science which may still be out there.'