Jens Lehmann (Germany)
Since 2008, the largest palaeontological association in Germany – the Paläontologische Gesellschaft – has awarded the crown for ‘Fossil of the Year’ for fossils that are of special scientific interest or that are commonplace in that they are on display in many institutions. A ‘Fossil of the year’ can also be easy to collect species, encountered by many amateur enthusiasts.
Among others, the largest ammonite in the world in the museum of Münster and the spectacular dinosaur skeleton of Brachiosaurus from East Africa in Berlin have won the title. This is the fifth time the award has been given, but is actually the first time the crown has been given to a fossil species and not to an individual fossil find.
This year’s title went to Arthropleura armata, a remarkable arthropod species resembling recent millipedes and centipedes (Fig. 1). However, details of the phylogenetic relationships of the order Arthropleurida to millipedes are still debated (for example, Krauss, 2003a, b). And the arthropleurids reached significantly larger dimensions, with a total length of more than two metres (Fig. 1) and, therefore, are the largest arthropods ever to have lived on land. The first occurrence of the genus Arthropleura dates back into the period of the massive coal swamps of the late Carboniferous and they became extinct at the end of the early Permian – during the first phase of the supercontinent Pangaea. Arthropleura lived 280 to 340mya, but related arthropleurids (order Eoarthropleurida) continued to exist into the Silurian.
Arthropleura is recorded from south-western Asia, North America and Europe. It is found as body fossil – remains of the actual animal – and trace fossils of its alleged locomotion tracks. Body fossils are mainly known from continental Europe, particularly Germany and Poland (the coal-mining area of Silesia), and Illinois (Mazon Creek). Very small but fairly complete fossils from France (Montceau-les-Mines in Central France) might belong to another genus. Due to its delicate nature, most of these body fossils are only known from fragments (Fig. 2). Furthermore, most fossils probably represent exuviae (that is, the empty skin of arthropods produced by moulting).
In the UK, most fossils attributed to Arthropleura are trace fossils. There have been a few body fossils found in Scotland and Somerset (for example, Proctor, 1998), but more famous are their alleged trackways. In Scotland, several coastal exposures of late Carboniferous sandstones contain arthropod tracks and they are most likely linked to Arthropleura,since no other large arthropods are known from this period. As an example, a track from the sandstones of the Isle of Arran is figured here (Fig. 3) and this occurrence is among many others in the wider area of southern Scotland (see also Arthropleura – a prehistoric bug hunt by Joe Shimmin and Stephen Day, in Issue 13 of Deposits and www.discoveringfossils.co.uk/crail_fossils.htm.
Arthropleura armata had already been discovered in the nineteenth century and was first described in 1854 from the late Carboniferous of the Saar coal-mining area in south-western Germany. However, it is also known from several contemporaneous localities in northern Germany today. These include the famous Piesberg locality in Lower Saxony, which is one of the largest quarries in Europe. In eastern Germany, Arthropleura is recorded from the early Permian, for example, from the Kammerberg geotope, south of Manebach in Thuringia.
The specimen figured here is from the rock dump of the Warndt mining shaft in the Saarland district (for locality details, see Kraus 2003b). It is one of the more rarely occurring juvenile finds (Fig. 2). All of these fossils from Warndt are associated with plant debris, including scale trees (Lepidodendron), horsetails(Annularia and Calamites) and various ferns and seed-producing plants (referred to as Sphenopteris). However, Arthropleura probably did not typically inhabit thecoal-forests. This would explain their rare occurrence in association with coal seams, where fossils are intensively collected. Their preferred habitats were rather mud flats, with their sparse vegetation, as well as river banks and deltas.
The mouth parts of Arthropleura have not been recorded yet. However, pollen in the digestive tract of small specimens indicates a vegetarian diet. The larger individuals probably were carnivorous with massive jaws.
The Paläontologische Gesellschaft is going to assemble for its annual meeting in one of the main regions where Arthropleura has been found – the Saar area in south-western Germany. The meeting takes place in the centre for biodocumentation and ‘‘Gondwana – Das Praehistorium’’ in Schiffweiler Reden. In this interactive museum, models of Arthropleura can be seen within a reconstruction of their palaeoenvironment. It also houses one of the most complete fossils of Arthropleura. There are many more places in Germany where excellent reconstructions are on display, as well as in other parts of the world were this fossil has been recorded (for example, in the USA in the St Louis Science Center). In the UK, there is a reconstruction in the Hunterian Museum in Glasgow, as Scotland is the best area to find Arthropleura in the country.
Kraus, O. (2003a): Fossil giants and surviving dwarfs. Arthropleurida and Pselaphognatha (Atelocerata, Diplopoda): characters, phylogenetic relationships and construction. Verhandlungen des naturwissenschaftlichen Vereins Hamburg 40: 5-50.
Kraus, O. (2003b): On the structure and biology of Arthropleura species (Atelocerata, Diplopoda; Upper Carboniferous/Lower Permian). Verhandlungen des naturwissenschaftlichen Vereins Hamburg 41: 5-23.
Proctor, C. J. (1998): Arthropleurids from the Westphalian D of Writhlington Geological Nature Reserve, Somerset. Proceedings of the Geologists’ Association 109:(2) 93-98.