marine reptile – More Than A Dodo

Pieces of a plesiosaur

We’ve just opened a brand new, permanent display called Out of the Deep, featuring two beautifully preserved plesiosaur skeletons. Remarkably, both of these marine reptile fossils have skulls, which is more unusual than you might think. Dr Hilary Ketchum, collections manager in the Museum’s Earth Collections and curator of Out of the Deep, describes how the skull of the long-necked plesiosaur made it safely from a quarry to a museum display.

At the bottom of a clay pit in 2014, palaeontologists from the Oxford Clay Working Group discovered a 165-million-year-old fossil plesiosaur skeleton, and they knew they had found something special. Plesiosaur bones are fairly common in the quarry, but skeletons are rare. Skeletons with skulls are rarer still. Fantastically, at the end of their newly-found plesiosaur’s neck was a skull. Barely visible underneath the clay, only the tip of the snout and a few teeth were exposed.

Can you see the skull? Fossil hunting in the quarry takes time, patience and a good eye to distinguish between bones and clay. Image: Mark Wildman, Oxford Clay Working Group.

Plesiosaur skulls are usually made up of around 33 bones, not including the tiny bones from inside the eye sockets, called the sclerotic ring. The skull bones are among the smallest and most fragile in the entire skeleton. This means they are much less likely to be preserved, and less likely to be discovered, than the larger and more robust backbones and limb bones.

A plaster jacket was made around the skull while still in the quarry.
Image: Mark Wildman, Oxford Clay Working Group.

When the plesiosaur skeleton arrived in the Museum in 2015, the skull and some of the surrounding clay was encased in its protective plaster field jacket. As tempting as it was, instead of cracking open the jacket straight away, we decided on a more technological approach. Professor Roger Benson and Dr James Neenan took the specimen to the Royal Veterinary College to use their enormous CT scanner, normally used for scanning horses and other large animals, and took thousands of X-rays of the jacket. This allowed them to build up a 3D model of the fossil inside – our first tantalising glimpse of the whole skull!

The CT scan of the plaster jacket (left) revealed the location of the skull inside the jacket (middle). The jacket was then digitally removed (right) to reveal a 3D image of the skull.

Having the CT scan of the skull was like having a picture on a puzzle box
Juliet Hay, Earth Collections conservator and preparator

Although the CT scan was incredibly useful, we still had to proceed with the preparation with caution. It was possible that not all of the bones had not been detected by the scanner, especially the incredibly thin bones of the palate.

After opening the plaster jacket, Juliet began to carefully remove the clay from around the fossil bone.

Slowly and carefully, Juliet and I removed the soft clay from around the skull. The weight of clay pressing on top of the skull for millions of years had crushed it, breaking some of the bones into a lot of smaller pieces. In order to keep track of them we attached a number to each piece of bone and photographed it from several different angles before removing it from the jacket.

Each individual bone was mapped using a numbering system. The numbers were attached with the conservation adhesive Paraloid B72 in acetone, so that they could be easily removed later.

The plesiosaur’s pointed teeth being revealed.

When all the bones had finally been removed from the clay, we had over 250 pieces. Next came the challenge of the three-dimensional jigsaw!

With knowledge about plesiosaur skulls from my PhD, and some extra expert help from Roger Benson and Dr Mark Evans, Curator of Natural Science and Archaeology, New Walk Museum and Art Gallery, I was able to build up the skull, piece by piece, until it was nearly whole again.

After many months of painstaking work, the beautifully preserved skull of this long-necked plesiosaur can finally be seen in the *Out of the Deep* display.

Amazingly, the skull is even more complete and more beautifully preserved than we could tell from the CT scan. The sutures between the individual bones can be seen in exquisite detail, and even though I work with fossils every day, I still find it amazing that it is 165 million years old.

With special thanks to:

Oxford Clay Working Group: Mark Wildman, Carl Harrington, Shona Tranter, Cliff Nicklin, Heather Middleton, and Mark Graham, who uncovered and excavated the long-necked plesiosaur.

Forterra, for generously donating the plesiosaur skeleton to the Museum, after it was discovered in a Forterra quarry.

A plesiosaur named Eve

A Spotlight Specimens special for Oxford Festival of Nature

by Juliet Hay, Earth Collections preparator and conservator

I feel myself very lucky to have a job that involves working with the fossil remains of long-extinct animals. One of the things my colleagues and I are currently working on is a plesiosaur – a marine reptile that lived in the sea millions of years ago.

This particular specimen was found in a clay pit near Peterborough by members of the Oxford Clay Working Group in 2014, and is a near-complete example of its kind. The palaeontologists who found the specimen named it Eve, although we don’t know if it was male or female, and perhaps never will.

The discovery of large fossil vertebrates like this is rare, so we are fortunate to have had the specimen donated to the Museum by the quarry owners Forterra.

The plesiosaur is 165 million years old and, when alive, was around 5.5 metres long. It had a long neck, a barrel-shaped body, four flippers and a short tail. The find is particularly exciting as the skull was also discovered. It is encased in a clay matrix, which is relatively easy to remove, but the work has to be carried out under magnifying lenses and microscopes.

As the skull is quite small relative to the size of the body, the features are very delicate and it is a painstaking process to remove the sediment without damaging the fossil bone or losing any tiny fragments. Fortunately, pictures of the skull have been produced using CT scanning technology, and the images are proving invaluable as an aid to assist in its preparation. It’s a bit like having a jigsaw puzzle with the picture on the lid to refer to!

sdfsd — A belemnite hooklet at 12x magnification, found with the plesiosaur remains and possibly part of Eve’s last meal

The clay covering the skull is being sieved and examined and tiny hook-shaped fossils have been found. These came from the arms of squid-like creatures called belemnites, which may have formed a large part of the plesiosaur’s diet.

It is too early to say for sure, but Eve could represent a species new to science, as some features, such as the shape of the flipper bones and some of the surfaces of the bone in the skull, are quite unusual. Further research needs to be done before the findings can be published in scientific journals – watch this space.

And if you’re visiting the Museum before 25 July, you can see some of the fossilised remains of Eve for yourself, in our Presenting… display case.