Cutting edge: Joshua B. Smith

Stepping down from the relative warmth of the Land Cruiser, I crunch across the sand for about 15ft to what looks like part of a blackened, burnt-out log. I kneel down closer - close enough so the wind can blow sand directly in my face - to see if my guess is correct. Yes - it is part of a fossil leg bone. This bone belonged to a very large animal. In fact, it is a piece of what has turned out to be the first new dinosaur found in this part of North Africa since 1935.

I stand and look north towards the area, some ten miles away, where the noted German palaeontologist Ernst Stromer sat on the back of a camel almost a century ago and recorded his finds in his expedition journals - noting the first occurrence of dinosaurs in Egypt.

Part of what drew me to Bahariya, in the desert 180 miles southwest of Cairo, was the diversity of species that Stromer described - not just dinosaurs, but other animals too. A bigger part was that Bahariya looked like an opportunity. Much of what Stromer's crews found was destroyed in an Allied bombing attack in the second world war and these losses have never been replaced. Before us, no team since Stromer had successfully recovered dinosaur material from Bahariya.

Capitalising on this opportunity, we secured some unconventional funding from Cosmos Studios and MPH Entertainment, a US film company, in exchange for allowing them to film; put together a University of Pennsylvania's Egyptian Geological Survey field team; spent endless days with dental picks, toothbrushes and shovels; and produced a new dinosaur.

We named this beast - reported in Science magazine in June - Paralititan stromeri , Stromer's giant by the sea, after Stromer, but, now that the fuss over its size (it may have been up to 31m long) and me being pretty young (now 31) is subsiding, what does the discovery really mean? What does Paralititan tell us? For that matter, why focus energy on studying old, dead animals?

Well, speaking for myself, we know rather little about what North Africa was like 94 million years ago and Paralititan helps to fill in the gaps. Also, unless history shows that dinosaurs can get a lot bigger, Paralititan is certainly one of the most massive creatures to have ever walked the earth and is helping to show us just how big terrestrial animals can get.

Beyond the dinosaur, though, perhaps the more pertinent question should be why do we care what North Africa was like almost 100 million years ago? In short, why are we interested in ancient environments? The answer can be summed up in a single word - change.

The sequence of rocks, the Bahariya Formation, that preserved paralititan records the existence of a very warm, tropical intertidal forest at a spot 94 million years ago where now there is almost nothing but sand and rock. A later sequence shows that roughly 45 million years ago the sea completely covered this part of Egypt.

The Sahara was not always a desert, and will not always be one. The earth is dynamic and ever changing. Understanding that the earth changes requires a perspective on ancient environments - and it is a point that should be acutely important to a species that desires to build vast, immobile cities on earth.

Why are we interested in ancient environments? How could we not be?

Joshua B. Smith is a doctoral student in earth and environmental science at the University of Pennsylvania and leader of the Bahariya Dinosaur Project.