Parabrontopodus?

Rob Hope (France)

Ahh, fossil footprints… concurrently tantalising, evocative and enigmatic! Hint fossils of footprints are identified all through the world, together with within the Jura Mountains of each France and Switzerland. Not too long ago, close to the tiny French village of Coisia, about 30km north of Geneva, a big slice of rock has revealed a whole bunch of dinosaur footprints. Unbelievable! I went alongside to analyze.

It was the Alpine orogeny (about 30 million years in the past) that thrust and twisted this large fossil-laden stratum into the vertical place seen at this time. Initially, it was an unlimited, flat, tidal seashore. The trackways have been dated to the ultimate stratigraphic unit of the Jurassic Interval, generally known as the Portlandian (generally additionally known as the Tithonian) about 141 million years in the past. Throughout these instances, large sauropods got here and went upon the mudflats. They left deep, rounded prints within the mud that baked within the tropical solar earlier than being coated by silt, deposited by subsequent tides. On this means, they have been miraculously preserved and, once more miraculously, they have been later (certainly a lot later) found.

In 2005, French palaeontologist, Jean Le Loeuff and colleagues investigated the location, earlier than publishing their conclusions within the French scientific journal Palevol. Hint fossil prints have organic names that describe their morphology (palichnology) and never the title of the animal that may have left them. Le Loeuff informs us that the well-preserved prints on the Coisia web site are of the ‘Parabrontopodus’sort, which means a narrow-gauged sauropod trackway (left by an Apatosaurus or possibly a European sort of Diplodocus).

A short time after this discovery, information got here of one more outstanding discover, once more in France’s Jura vary. In an deserted, weed-ridden quarry, close to the hamlet of Loulle, but extra dinosaur footprints have been found. In all, 1000’s of prints will be seen there, with a number of particular person trails operating for tens of metres. Even Juvenile fossil tracks are preserved, which run parallel between bigger trails. Have been grownup sauropods defending a teen as they wandered collectively upon these as soon as soggy flooring, an estimated a number of million years earlier than the Coisia footprints have been laid down? Analysis was carried out on the trackways, led by JM Mazin of Lyon College (see Le Loeuff et al., 2006; Mazin et al., 2016).

I attended a convention, organised by Mazin and main geologist, P Hantzpergue on the interpretation of the Loulle quarry trackways. They defined that the weird cracked floor facet of this fossil web site was on account of a skinny, slimy algae overlaying the as soon as sodden, gluey silts. This brackish ecosystem was established lengthy earlier than the sauropods had walked throughout them. Due to this fact, in contrast to the Coisia setting, this was not inside a tidal setting.

One single fossil print right here is actually astonishing (see Fig. 1, with beer bottle indicating tough scale). The unique melancholy, created by the good weight of the lumbering animal, stays wholly intact. And surprisingly, this explicit print survives in isolation. Why is that this particular fossil so exquisitely preserved, whereas the rest of the path has been completely obliterated? We don’t know.

Fig. 1. Dinosaur footprint with beer bottle for scale. The unique melancholy, created by the good weight of the lumbering animal, stays wholly intact

On account of the singular facet of this outstanding footprint, identification of the palichthyospecies can’t be established. It could be that the animal that trod right here was of a Parabrontopodus species or a brontopodus (a wide-gauged sauropod path) species. We are going to most probably by no means know.