The Palaeozoic terrestrial arthropods of Scotland

Scotland is remarkable for yielding a high diversity of different terrestrial arthropods from the Silurian, Devonian and Carboniferous periods, often from particular times when they are unknown elsewhere in the world. The most notable discoveries include Pneumodesmus newmani Wilson & Anderson, 2004 – a millipede (Diplopoda) from the mid-Silurian of Stonehaven, Aberdeenshire, which is the earliest known fully terrestrial animal, as demonstrated by the presence of spiracles. This specimen suggests that other contemporary diplopods were also terrestrial. The Rhynie and Windyfield Cherts from the Early Devonian (Lochkovian) of Rhynie, Aberdeenshire, are remarkable for preserving the earliest known terrestrial ecosystem in the world, consisting of plant stems in situ, preserved at the cellular level, along with a diverse arthropod fauna including the earliest known hexapods (Rhyniella praecursor Hirst & Maulik, 1926, Rhyniognatha hirsti Tillyard, 1928 and Leverhulmia mariae Anderson & Trewin, 2003 – see Fayers & Trewin [2005]), along with trigonotarbid, acarine and opilionid arachnids, and a scutigeromorph centipede (Chilopoda). Scotland has also yielded a diverse Early Carboniferous (Visean) diplopod, scorpion and opilionid fauna from East Kirkton, West Lothian. A recently discovered slightly older (Tournaisian) diplopod and scorpion fauna from Chirnside and Burnmouth, Berwickshire, along with numerous amphibian, plant and other invertebrate remains have filled ‘Romer’s Gap’ and demonstrate that this perceived gap was due to a lack of suitable non-marine deposits of that age rather than a dearth of terrestrial life due to low oxygen levels. Finds from the Late Carboniferous are much rarer than from other parts of the UK due to most of the Westphalian C and D deposits having been subjected to deep weathering, which removed the organic components and thus the deposits were not exploited for coal.