Winterswijk quarry

Amateurs have found more here than the world's main fossil database knows about.

Utrecht University researchers compared what has actually been collected from this quarry against the Paleobiology Database and found that between 51 and 67 per cent of Winterswijk's real richness, depending on taxonomic rank, is simply not in it. Coverage is uneven: 86 per cent of the arthropods had been entered, while the molluscs were entirely absent. Even with that missing data Winterswijk ranks among the richest Anisian marine fossil sites in the world, and it ranks first of all of them for ichnogenus richness, meaning trace fossils. That assessment, the researchers say, is largely the work of the citizen scientists who have been collecting and documenting here since the 1950s.

The rock is Muschelkalk, a limestone built from very fine silt settling on a sea floor over millions of years into beds tens of metres thick, later pushed up to the surface. It was found in 1852, when a borehole went down 112 metres here looking for coal and hit this instead.

The quarry itself began with a hunch and a meadow. A haulage contractor from Winterswijk and some friends dug holes in a field to see whether anything economically useful lay underneath, carrying every stone they found to the mayor, who had them examined by the provincial chief engineer. Some of the stone went straight into road surfacing, the meadow was bought up so more could be dug, and the quarry opened officially on 4 August 1933 with the mayor present.

The fossils are exceptional because of how the mud dried. Shrinkage cracks opened between the layers as the flats dried out, and because of them the rock splits cleanly. Split it and you can find the footprints of animals that walked across that mud.

The headline animal is a marine reptile. A complete and perfectly preserved skull of Nothosaurus winterswijkensis was found here, along with skeletal parts and trackways. It lived about 240 million years ago, had an amphibious life, and reached about two metres.

The setting is unusual in its own right. With the old Jacobskerk in the village as the centre, rocks from the Triassic, Jurassic, Cretaceous, Oligocene, Miocene, Pliocene and Pleistocene all sit within a seven-kilometre circle, which is why this part of the Achterhoek is called the mosaic floor of the Netherlands. The quarry runs open days and excursions, and you can picnic in it.