Chalking With Dinosaurs, part 4

I don’t even work on dinosaurs, and here I am, yet again, writing about the crunching great lizard monsters and their footprints. It’s all a very elaborate ruse to get you hooked on ichnology, such that I can then start making videos such as Crawling With Ragworms and Irrigating With Thalassinids.

This is the good stuff! Dr Richard Callow admires the Jurassic fossil crustacean burrows of Filey Brigg.

Hey ho, it’s all good fun, and here we are with part 4 of Chalking With Dinosaurs, where we try to work out what kind of dinosaur made the big Burniston Bay footprint described by Martin Whyte and colleagues in 2006, and which hopefully you’ve chalked onto your yard/alley/driveway by now.

As I mentioned last time, there are plenty of Jurassic dinosaur footprints to be found on the Yorkshire Coast, but there are remarkably few dinosaur body fossils. Martin Whyte, Mike Romano and Will Watts summarized this in their 2010 paper, for which the key phrases are ‘scarce’ and ‘largely indeterminate’. In the splendid ‘Yorkshire’s Jurassic World‘ exhibition at the Yorkshire Museum there is a single sauropod vertebra, which can’t be assigned to a species, and is therefore known as Alan.

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! (image from Wikimedia Commons)

Might Megalosaurus, the original dinosaur, have made the big Burniston fossil footprint?

It seems a very good candidate, being of the right age and right dinosaur group. Interestingly, though, the calculated leg length we obtained from the Burniston footprint (2.2 metres, after Whyte et al‘s (2006) estimate of the foot having been 0.55m long, and Alexander’s (1976) equation of dinosaur hip height being four times its foot length) is longer than that known from fossils of Megalosaurus.

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…