Dinosaurs Rediscovered

by Michael J Benton

  Close-up of the hadrosaur, showing the tail flipped round along the backbone.

  Gridding and mapping the hadrosaur skeleton.

  Mapping came next. In those days, we did this by means of field sketches and photographs. We marked out metre squares across the site using strings, and these were the guide for close photography and drawing on squared paper. We could identify most of the bones – indeed the skeleton was pretty complete, and individual bones had only been rotated or moved a short distance by river currents.

  Palaeontologists still, of course, draw and photograph their sites, but now they also commonly employ digital photographic techniques that record a perfect 2D or 3D model of the site, often called photogrammetry. The simplest form of photogrammetry is to take numerous overlapping photographs and then use standard software to blend the images together into a single large image covering the whole site. This software is like the landscape feature in many digital cameras that allows you to take a few photographs in sequence and merges them together.

  More useful is 3D photogrammetry, where the photographs are combined to reveal the whole landscape, showing bones above and below each other, at different levels, and with sufficient fidelity to allow accurate measurements to be taken. The best efforts are achieved when a surveying set-up is used, with the camera on a tripod at fixed locations that are keyed to each other, so the angled photographs reveal all dimensions. Photogrammetry is now commonly used to record dinosaur footprint sites, for example, where the intricacies of the depth and detail of each print can reveal something about how the dinosaur distributed its weight as it walked or ran (as we shall see in Chapter 8).

  After the bones had been mapped, we began to remove them from the rock. This required planning and some risk. We could not simply lift the whole skeleton, as it would have been too wide across to fit on the truck, and in any case would have weighed more than 20 tonnes (44,100 pounds) in the rock. We were stuck up a steep-sided coulée, and no heavy lifting machinery could come close. There were some gaps between blocks of the skeleton, so we could dig deep cuts between these blocks, and we then created a system of deep trenches into the rock so that each cluster of bones was isolated on an upstanding island.

  The next step is just what the early bone hunters soon learned. If you lever dinosaur bones out of the rock they break; covering them with a plaster cast would preserve them until they could be transported home. We mixed wet plaster in washing-up bowls, ran strips of burlap (sack cloth) through the plaster, and laid this criss-cross over the bones after protecting the bone surface with layers of kitchen paper. The idea was to build up a solid cocoon six or seven layers thick, and strengthen it with handfuls of plaster sculpted over the surface. After a day of plastering, your hands are dry and cracking.

  Use of power tools to remove rock from above the bones.

  Applying sackcloth strips and plaster to strengthen the bone-bearing block.

  The plaster cocoon would take several hours to set, and it had to lap down to the rock below the bones. Once primed, we inserted chisels and pry bars under the bone, and attempted to flip it. This is easy if the block is no more than human-sized, but to free the largest block we had to rig up a block and tackle above it, and run several chains into tunnels burrowed beneath. The block eventually flipped onto its side without fragmenting. Then, we cleared out all the rock we could from underneath the bones, and plastered the underside to make a complete, solid parcel.

  The smaller bone parcels were carried by hand down to the truck. The medium-sized ones were mounted onto a curious contrivance consisting of a single bicycle wheel beneath a wooden frame, which could be guided by two people, one in front and one behind. This was precarious, and sometimes ran away, but nothing was damaged. The final block, weighing more than a tonne, sat in the debris of the excavation site, several miles from the nearest road, and 100 metres (328 feet) above the nearest point on the river bank to which the truck could approach. We therefore had to dig out a straight road down to the truck so it could line up with the dig site, and hauled the block down the slope using the vehicle’s front-mounted winch and some long chains. We built a loading platform from rock, and managed to winch and coax the great block onto the load bed. If only we could have used a team of horses to drag the blocks on those steep slopes!

  Clearing out loose rock from beneath a 1-tonne (2,205 pound) flipped block containing dinosaur bones.

  Our pathway down to the truck; every step of the 1980 dig was filmed.

  How are the bones extracted from the rock?

  Back in the laboratory, the bone packages are laid out on benching, ready to be extracted. The plaster casing is removed using a small circular saw, and exposed bone is consolidated, usually with a soluble glue that soaks deep into the cavities, but which can be removed by solution in acetone (for example). A decent dinosaur preparation laboratory is laid out with numerous well-lit work stations, one for each technician. Each station is equipped with dental drills and other mechanical tools to remove rock, and there should be vacuum systems above the benches to remove the dust safely.

  The physical removal of rock is done by sweeping a dental drill parallel to the bone surface – not aiming straight at it – in the hopes that chunks of rock will jump free, and thereby avoid nicking the bone surface with the drill. The technician keeps cleaning and consolidating the surfaces using soluble glue. You might think a fossil bone would be tough – well, they are, but tough and brittle, and consolidation is needed constantly to preserve the bone.

  Each bone might take a day or more to free from the rock, and must be carefully numbered, tracked, and matched to the field map so they can be accurately reassembled later, if need be. The large block we collected took weeks to clean up, as many bones lay over each other, and each rib and vertebra had to be freed to get to the bones beneath. Sometimes, if the bones are too intimately entwined, they are left in the rock.

  These methods are all long established, because they require the human eye and hand to work in coordination, there is no way to automate the process. However, technology now offers some amazing new opportunities. In the case of delicate structures, such as braincases, or small skeletons, the whole specimen can be X-ray scanned. This is computerized tomographic scanning, often shortened to CT scanning, in which the scanner captures X-ray images of the internal structure of the bone or rock, and these can be viewed as if they are a stack of slices, spaced maybe fractions of a millimetre apart. This means that museum preparators do not have to risk damaging delicate specimens, say a dinosaur embryo inside its egg, instead capturing a perfect 3D image.

  Back in the lab, clearing more rock from the plaster jacket.

  A typical day in the SEM lab in Bristol: David Attenborough pops by in 2017 to see Fiann Smithwick at work.

  CT scanning of fossils has only become commonplace in the twenty-first century, when scanners, developed first for medical use, became cheap enough that every university or museum could afford one. We commonly scan fossils up to the size of a magnum bottle of champagne; above that, and they have to go to industrial or veterinary scanners designed to scan an aircraft engine or a horse.

  The image stacks provide the information for a 3D digital model. Generally with fossils irregularities in the rock complicate the picture, and students sometimes have to spend weeks editing the scan slices, digitally removing irregular rock grains, bits of fossil shell, and other debris. They can also colour code the different elements of the fossil, and then use the 3D model for further experiments to test, say, its engineering properties in feeding or locomotion.

  Other advanced technological applications can also be applied to dinosaurs. For example, in our quest to identify the colour of dinosaur feathers, we used a scanning electron microscope, which enables scientists to see structures that are much smaller than can be viewed under a regular optical microscope. A light microscope allows scientists to see objects down to one-thousandth of a millimetre across, whereas a scanning electron microscope ta
kes this to one millionth of a millimetre. We also use the scanning electron microscope to map the chemicals present in fossil bones or feathers, showing whether they were preserved as calcium phosphate or clay minerals, or were enriched in any other chemicals, such as iron or copper, that might give a clue to the mode of preservation. Palaeontologists now use the latest mass spectrometers, instruments that can identify inorganic and organic chemicals, even in tiny quantities, and which are becoming essential in the study of colour and the survival of any organic materials in dinosaur fossils.

  How do we see the whole animal?

  Once the bones have been collected and brought back to the lab, there are two further steps. First, the skeleton can be mounted for show in a museum; and second, its living form can be reconstructed by restoring soft tissues such as muscles, sense organs, and skin.

  Once the bones have gone to a museum, the skeleton is built up in its correct configuration using a metal framework called an armature, which is strong enough to hold the bones, and shaped in such a way that the whole skeleton is arranged correctly and posed in a reasonable way. Some aficionados used to like to hide the armature inside the fossil bones, so great holes had to be drilled through the vertebrae so they could be threaded on to it, like half-tonne cotton reels. Now, every effort is made not to damage the bones, and indeed the armature may be visible.

  How can the skeleton be put together correctly? We all know the kids’ movies and cartoons in which the bones are strung together randomly, and perhaps the head is popped on the end of the tail. Well, in many cases, as in the excavation I did in Dinosaur Provincial Park, the skeleton is preserved more or less unperturbed, and with all bones in the right places. In any case, palaeontologists are like surgeons – they can immediately identify what each bone is – left femur, right humerus, dorsal vertebra, and so on. This is what they are trained to do. If anything is missing, the museum technicians can make casts of some ribs or vertebrae from their neighbours, or they can flip a right femur, say, to make a left femur. The symmetry and repeatability of the skeleton mean it’s pretty clear when they get it right or wrong.

  In travelling dinosaur shows, the skeletons are usually casts, often in artificial materials such as fibreglass, which makes them light and tough – easy to transport in pieces from venue to venue. The museum technician first paints the original bones with a rubber compound to create moulds, constructs a tough supporting cradle, and then separates the two or more pieces of the moulds, releasing them from the bones. These moulds can then be used to produce as many casts as are required, and the casts will show every fine detail of the original bone.

  How can flesh be put back on the museum bones? Normally, this is done through a conversation between the palaeontologist and the artist. The skeleton carries many clues to the location and nature of soft tissues. For example, muscles generally attach to the bones at each end – the biceps muscle in the arm, which body-builders like to show off, attaches to the shoulder blade and to the main bone of the forearm, the ulna. This muscle, and indeed most of the other main muscles of the arms and legs, are pretty much the same among mammals, birds, and crocodiles, so they were probably comparable in dinosaurs. The sites where muscles attach to the bones often leave clear rough patches, and these can be used to reconstruct the angles and sizes of muscles in a dinosaur.

  Muscles, skin, eyes, and tongues are put in place using any clues that exist on the bones, but otherwise by comparison with modern animals. Later chapters will reveal how modern palaeobiological studies have told us a great deal about how dinosaurs reproduced, grew, fed, and moved, and all this new knowledge is used by the artist in restoring their image of the living dinosaur – whether it’s a painting, a 3D model, or an animation. We can now even restore feathers and colours in some cases.

  How can dinosaurs be used in education?

  Museums have a key function in education. All the effort and expense of digging up dinosaurs and bringing them back to the museum can be justified partly in terms of the science. In addition, a key duty for museums, and indeed a key duty for university professors, is to take their science out to the public. Here is one example of how the crossovers between practical work, science, and education can work together.

  Over the past twenty years, the University of Bristol has run a programme called the Bristol Dinosaur Project. Since 2000, the team has visited hundreds of schools and spoken to tens of thousands of children, as well as appearing at science fairs in Bristol and elsewhere. The Bristol dinosaur, Thecodontosaurus (see overleaf), was named in 1836. It may not seem very exciting because it is known only from isolated bones, and it’s quite a small plant-eater, not much larger than an eight-year-old child. Nevertheless, children love to hear about the dinosaur that stomped around their city some 208–201 million years ago, in the Late Triassic.

  Children look at the Bristol dinosaur Thecodontosaurus at an educational festival.

  We use the dinosaur as a way to get children of all ages thinking about key science topics, such as geological time, continental drift, climate change, evolution, and biology. It helps enormously that we talk about the sciences, as in this book, in terms of testable ideas. Then the kids can follow through the calculations, say, of dinosaur running speed, and they see how it makes sense.

  In the initial years, when we had a full-time Dinosaur Education Officer, we visited 200 schools and spoke to 10,000 children each year. Then, the Bristol Dinosaur Project received substantial funding from the UK Heritage Lottery Fund, and it was able to operate at a much more ambitious level; after the funding ran out, we had to scale back, but continue with enthusiasm. Our students love having the chance to try out their teaching skills, and to talk to young enthusiasts about what they love to do.

  Genus:

  Thecodontosaurus

  Species:

  antiquus

  Named by:

  Henry Riley and Samuel Stutchbury, 1836 (genus); John Morris, 1843 (species)

  Age:

  Late Triassic, 208–201 million years ago

  Fossil location:

  England

  Classification:

  Dinosauria: Saurischia: Sauropodomorpha

  Length:

  1.2 m (4 ft)

  Weight:

  40 kg (88 lbs)

  Little-known fact:

  This was the first dinosaur ever to be named from the Triassic.

  We speak to two age groups, seven- to nine-year-olds, and fourteen- to fifteen-year-olds, and the style is different with each. With younger children, it has always been very easy to engage their enthusiasm – they just love it when you pass round a dinosaur bone or tooth, and they are thrilled to be handling the real thing. With the teenagers, it is more important to let them see how much fun a career in science, or a related field, can be. We use a kind of forensic approach – here’s a mystery that seems impossible to solve (‘how fast could T. rex run?’ or ‘which month did the asteroid that wiped out the dinosaurs strike?’), and then step the students through the evidence and the basic theory they need. We are trying to engage them in science, showing them it can be fun, and why they need to study maths, biology, chemistry, and physics if they want to pursue it as a career.

  The Bristol Dinosaur Project visits schools, but does many other things. Twice, it has been associated with outdoor exhibitions of animatronic dinosaurs at Bristol Zoo; these attracted tens of thousands of visitors. We work with Bristol City Museum and other museums, providing the enthusiastic personnel to talk to visitors; our students can answer questions in a personal way and use their own experiences to give down-to-earth answers.

  The Bristol Dinosaur Project has also been a great vehicle for giving undergraduates their first research experiences. We can’t offer them dinosaur bones for study, but there are associated projects, particularly on microvertebrates, such as the teeth of sharks or tiny bones of other fishes and reptiles. There are many cliffs and old quarries around Bristol that have yielded fossil-rich rocks, and we focus
on concentrations of bones both in bone beds laid down on the seabed and on cave fills that include fossil bones. The students love the chance to do fieldwork, and they have to train their eyes to pick out the tiny bones and the bone beds in the rock sections.

  The biggest challenge for the students is to organize their work into the correct, professional style for scientific publication. This is a steep learning curve, but so far twenty-five students have taken the projects to completion – and the publications help them advance their careers. Five or six successful palaeontologists can trace their careers back to such early experiences. This would seem to be a natural endpoint of the process we have traced in this chapter, all the way from digging up the bones to learning something new from them.

  Digging up dinosaurs is one of the best things a palaeontologist can do. The field methods haven’t changed much for over 150 years – nothing beats a good pair of eyes, and some strong shoulders! Three things have improved about the fieldwork. First, it’s quicker and easier to travel around the globe, and so palaeontologists can now work in many parts of the world; this has the wonderful side-effect of encouraging more collaboration between young scientists from different countries than ever before. Second, we observe more, and especially about the context of the bones. This provides key sedimentological data for interpreting the ancient environments in which the bones have been preserved. Third, and associated with this, we are better at mapping the sites and better at recording the finds and making sure that nothing is lost, especially tiny fossils of fishes, frogs, or lizards that lived under the feet of the dinosaurs.