After an interval of many months, I’ve been prompted to finally produce a fifth part of Chalking With Dinosaurs, featuring me making footprints in the sands of Scarborough’s South Bay, and then hunting dinosaur footprints in the rocks of the South Cliff:
We immediately found ourselves thinking: “That would be cool with dinosaur feet!”
Then we thought “Actually, it would be cooler with correctly sized dinosaur feet that could produce some sort of trackway…”
So this is what we did…
1) Get together all the kit you might possibly need (different sized tubes for rolling, cardboard for making feet with, pens and pencils, tape measures, scissors, cocktail sticks/kebab skewers to attach the feet to the rolling tube).
All the kit you need to make a rolling dinosaur foot trackmaker!
2) Decide that the smallest tube needs to be an ornithopod, the medium-sized tube a theropod, and the largest tube a sauropod. Measure the diameters of the tubes to work out the ‘hip height’ of the dinosaur (the fully extended length of the leg when the foot hits the ground), and divide that number by 4 to come up with a proportional size for the foot.
Tube diameter (leg length) = 45 mm, so foot length = 11.25 mm
Tube diameter (leg length) = 94 mm, so foot length = 23.5 mm
2b) Then remember that sauropods aren’t quite the same as ornithopods or theropods, and consult a paper by Bernardo J. Gonzalez Riga to come up with some better-looking numbers. Decide to save the sauropod rolling trackway making for next time.
3) For a bit of ancestral accuracy, use the feather of an extant theropod to colour in the tiny feet of your rolling theropod trackmaker.
4) Cut out the feet, tape each of them onto a short bit of cocktail stick, then tape them to the inside of the rolling tube. Then realize they’re not thick enough to touch the ground when the tube rolls, so take them off again and add more card until they are. We did this for the ‘ornithopod’ on the small tube, though the challenge of cutting out small cardboard feet accurately means they are best described simply as tridactyl.
5) Find a reasonably large tray and cover with some kind of soft sediment. In this case, I used gardeners’ silver sand, but I’m sure flour or salt or sugar could work.
6) Roll the foot-bearing tube across the sand to see if it works, and – hey presto! – a dinosaur trackway. Yes, ok, it’s a one-legged dinosaur with an implausibly wide gait, but this is a work in progress!
A dinosaur trackway made in fine-grained sand by a rolling tube on my kitchen table. Fossilization potential: low.
7) To work out how fast the dinosaur was moving, measure the stride length. Here it was 150mm, give or take:
Trackway stride length, measured from heel to heel.
(I’m not aware of any evidence from the trace fossil record of tiny, wide dinosaurs hopping at high speed, but at least now we know what kind of trackway we’re looking for.)
Another – probably more genuinely ichnologically useful – thing is that, even with just two footprints made by the same cardboard foot in uniform dry sand, we can see that there is variation in track morphology. The second footprint is a much more accurate representation of the cardboard foot than the first one.
Footprint 1 of the tiny rolling dinosaur trackway.
Footprint 2 of the tiny rolling dinosaur trackway.
I will write this up as an activity sheet in due course, and get back on with chalking those dinosaur trackways, like I promised.
That doesn’t mean, however, that we can’t speculate reasonably about what might have made the big Burniston footprint. The evidence presented by Whyte et al. (2006) suggests strongly that the footprint is that of a large theropod, and Middle Jurassic rocks in Oxfordshire have yielded fossils of exactly that:
Megalosaurus was big, but its legs don’t appear to have been 2.2 metres long, even in the largest specimen (image from Wikimedia Commons).
So, is Megalosaurus not big enough? Did Yorkshire have a mega-Megalosaurus, or is there a possibility our calculations might be awry? Could the foot length obtained from the big Burniston footprint be an over-estimate?
To investigate this further, we need to stay in Oxfordshire, and combine the body fossils of Megalosaurus with the trace fossils of Ardley Quarry, and the research of Julia Day and colleagues, published in 2002 and 2004. And to really annoy you all, I’m going to save that for Chalking With Dinosaurs, part 5, when we can also work out how fast a large Middle Jurassic theropod dinosaur might have been able to run…
On Saturday May 9th 2020, as promised, I chalked a load of dinosaur footprints onto my driveway.
Two cardboard cut-outs of Yorkshire dinosaur footprints, and some chalk.
My video below explains what I did, and what a single footprint can tell us about the tracemaker. WARNING: this video features some low-quality singing.
If you want to go chalking with dinosaurs, here’s my checklist:
1. Choose a footprint you want to chalk. I decided to start with the big Burniston footprint described by Martin Whyte and colleagues in 2006. However, you might want to chalk a completely different dinosaur footprint, or your own footprint, or invent the footprint of a creature even more fantastical than a dinosaur.
2. Draw the footprint onto a piece of card and cut it out, to keep your footprint chalk drawings consistent.
My cardboard version of the big Burniston footprint (Whyte et al. 2006), with the interpreted size of the dinosaur foot highlighted, and my left foot shown for scale.
3. Get your chalks, work out where you want your footprint to go, and start drawing. If you don’t have a driveway, an alleyway or a yard will do just as well. If you don’t have outdoor space for chalking, draw the footprints onto paper indoors.
4. Measure the footprint. Is it the same size as the tracemaker’s foot? This can be quite hard to determine from a trace fossil, but the answer is often no. Martin Whyte and colleagues decided that, although the large Burniston footprint was 0.61m long by 0.49m wide, the squidgification* around the edges of the footprint suggested that the dinosaur foot itself was probably 0.55m long by 0.40m wide (hence my annnotation in the figure above).
5. From the size of the tracemaker’s foot, you can then estimate the size of its leg. How? Well, take some measurements of your own leg. My foot is 0.265m long, and my hip height is 0.91m, so that gives a ratio of hip height (h) to FL (Foot Length) as follows:
h = 3.43FL
If that ratio was true for the Burniston dinosaur, its foot length of 0.55m would yield a hip height of 1.89m (which is taller than me!).
A Tyrannosaurus rex and a 1.8m tall human (image from Wikimedia Commons). I am 1.8m tall.
That would make the hip height of the big Burniston tracemaker 2.2 metres, which is taller than most humans.
7. Unsurprisingly, then, the big Burniston footprint was made by a big beast, but what kind of beast exactly? The three-toed (tridactyl) print with a V-shaped heel and distinct claw marks strongly suggests it was a theropod (hence the title of Whyte and colleagues’ 2006 paper). However, there are no Burniston bones to confirm this, and no skeletons of Middle Jurassic theropods are known from Yorkshire. So what kind of theropod was it?
Examples of some of the largest theropod dinosaurs (image from Wikimedia Commons).
For that, you’ll have to wait for Chalking With Dinosaurs, part 4!
A chalk-outlined theropod footprint from Utah, with my left foot for scale.
As GeoWeek 2020 starts on Saturday May 9th, so does Chalking With Dinosaurs. And since we can’t all go to the Dinosaur Coast this weekend and hunt fossilized footprints, let’s bring the dinosaurs to our streets, our driveways, and our houses.
My video below gives an introduction to Chalking With Dinosaurs, and the science of ichnology. The Jurassic rocks of Yorkshire really are among the world’s best for finding dinosaur footprints!
Where exactly can you find footprints (once the Covid-19 travel restrictions are lifted, of course)? This is explained in my second video, below, but from Port Mulgrave in the north to Yons Nab in the south, the North Yorkshire coast has loads of places where dinosaur tracks have been discovered.
But if you want to get some dinosaur footprints chalked on your street, and then learn how we interpret such fossils and work out how dinosaurs might have behaved, you’ll have to follow the hashtag #ChalkingWithDinosaurs over the next few days, mostly on Twitter.
All together now: “Open the door, get on the floor, everybody chalk a dinosaur…”
The Yorkshire Coast is one of the best places in the world to walk with dinosaurs. The Jurassic rocks exposed between Staithes and Scarborough have yielded huge numbers of fossil dinosaur footprints, and scientists from all over the world come to North Yorkshire to better understand how dinosaurs lived and behaved.
My left foot, standing on a Middle Jurassic dinosaur footprint on the North Yorkshire Coast.
In the absence of being able to go and look at the rocks ourselves, I will be leading an online activity called “Chalking with Dinosaurs” during GeoWeek 2020, which runs from Saturday May 9th to Sunday May 17th 2020.
The activity will begin at 1530 BST on Saturday May 9th, and aims to tell people more about the rocks and fossils of Jurassic North Yorkshire, describe a few of the fossil footprints that have been found there, and – using some pavement chalk on my own driveway – explain how to make your own dinosaur trackways, and then interpret them. That way, when we’re finally able to get back out onto the coast, you’ll be able to give those Jurassic beasts a run for their money.
Oh yes, and if you have a go at #ChalkingWithDinosaurs yourselves, I have some prizes for the best entries received during GeoWeek 2020!