THE MOST SIGNIFICANT RECORD OF “MIDDLE”- LATE PALEOZOIC VERTEBRATE COPROLITES: SILURIAN-CARBONIFEROUS ICHNOASSEMBLAGES FROM SCOTLAND

The Silurian-Carboniferous represents the most important period of evolution for aquatic vertebrates, with major phylogenetic originations (e.g., Actinopterygii, Sarcopterygii) and extinctions (e.g., Heterostraci, Placodermii), functional innovations (e.g., tetrapody) and ecological diversification. Coprolites preserve evidence of feeding and digestion and thus should serve as proxies for phylogenetic and functional diversification. The best preserved record of vertebrate coprolites of Late Silurian-Early Carboniferous age is in Scotland, with the majority of samples reposited at the Hunterian Museum in Glasgow and the National Museum of Scotland in Edinburgh. Principal localities are in the Midland Valley and Northern Highlands, and many are associated with classic fish fossil assemblages of the Old Red Sandstone. The largest Silurian collection is from the Wenlockian locality of Birk Knowes, Lesmahagow, Lanarkshire. The most significant Early Devonian coprolites derive from the Lochkovian Tillywhandland Quarry, Forfarshire. The Achanarras Quarry (Eifelian–Givetian), Caithness, yields a large sample of Middle Devonian coprolites. Other Middle Devonian coprolites derive from Orkney, Moray and Caithness. We have not examined any Late Devonian coprolites from Scotland, but have studied a sample of this age from the Escuminac Formation in Quebec. In Scotland, there are large collections of coprolites from three Middle Mississippian (Viséan) localities: (1) East Kirkton, West Lothian; (2) Wardie, Midlothian; and (3) Anstruther, Fife. Very large coprolites from East Kirkton do not derive from eurypterids. The Late Mississippian (Serpukhovian) of Bearsden, East Dunbartonshire yields a large sample of coprolites. Smaller samples occur in several other Carboniferous localities. An initial analysis indicates that Late Silurian coprolites are generally comprised of macerated fish debris, with minimal interstitial groundmass. Groundmass-rich cylindrical coprolites, some spiral in morphology, become common in the Devonian. Coprolites longer than 100 mm first occur in the Carboniferous.