Hairy Museum of Natural History

…according to an impressive fossil trackway reported from the Carboniferous of Scotland.

The ichnofossil, described in the latest issue of Nature, shows the trail left by a 5-foot long eurypterid (your-IP-ter-id) as it hauled its body over a 330,000,000 year-old beach. Eurypterids were aquatic relatives of scorpions that thrived during the Paleozoic Era. Eurypterids were some of the top predators of their time, growing to a length of 6 feet and sporting nightmarish claws, which were the likely end of many of our fishy ancestors. Fossils of eurypterid exoskeletons are known from marine and freshwater deposits, but it has long been uncertain whether they were able to leave the water and crawl ashore.

A menacing eurypterid provides the impetus for lobe-finned fish to crawl onto the nearest beach in this detail of a mural by Margie O’Brien at the New Mexico Museum of Natural History and Science. A trackway reported from Scotland shows that these large aquatic invertebrates were coming ashore around the same time.

Unlike the menacing predator shown here, the trackway was likely made by Hibbertopterus, one of a group of eurypterids that had comb-like paddles instead of pincers. These paddles would have been used as filters to trap small invertebrates and other tiny prey items, so it is doubtful that this particular trackmaker was chasing any early tetrapods ashore.

The 20-foot long trackway preserves traces of six of the animal’s limbs digging into the muck and pulling its heavy tail behind it. The Nature article presents a photo and diagram of the trackway along with a reconstruction of the trackmaker, and a larger photo of the tracksite can be seen at BBC News.

—Matt Celeskey.

File under: Carboniferous, Recent Discoveries.