On the news last night we watched fascinating footage of dinosaur footprints, found at a location in somewhere near Nelson, in the South Island. (A secret location – if their whereabouts should become widely known, you can bet there’d be unscrupulous fossil hunters in there, chipping out slabs of rock with footprints in them, for sale to equally unscrupulous collectors.) While dinosaur trackways have been found in a number of other countries, this is a first for New Zealand. Joan Wiffen would, I think, have been delighted :-)
The footprints were found at several places over 10km or so. It seems that they were made by sauropd dinosaurs walking across tidal mudflats – the footprints would have been quickly covered by sediments when the tide came in. At one site there are 20 footprint impressions (a ‘trackway’), which is great as they can be used to give an indication of how fast the animals were moving. Using data on stride length (from trackways) and estimates of mass from skeletal features, it’s possible to estimate an animal’s speed. (There’s an on-line calculator that will let you work this out, if you should be so lucky as to find a trackway of your own. And certainly it’s possible to predict where more such finds could be made, in similar sediments of the same age.) Some of those estimates seem excessively high (eg 88kph), but still it does appear that dinosaurs could get up to some fairly impressive speeds, given the sizes that some of them attained.
It’s worth remembering that not all dinosaurs were the giants of popular perception. Computer simulations have suggested that the fastest of all was the tiny Compsognathus (at an estimated 3kg, the same size as our ditzy Burmese cat), which could have left Usain Bolt in the dust. The fact that even large dinosaurs could reach speeds of several kph when walking has been used to suggest that they were homeothermic, capable of maintaing elevated body temperatures. This may have been more likely in the larger animals, where mass homeothermy would come into play (large bodies will warm up more slowly, from the sun’s heat or by exertion, but will also cool more slowly). Perhaps the most readable discussion of dino homeothermy remains Bob Bakker’s entertaining (& still, in places, controversial) book The Dinosaur Heresies.
I’ll look forward to the scientific description of this discovery, due to be published next month. But in the meantime, isn’t this just such exciting stuff?