Terrestrial, fluvial and marginal lacustrine ecosystems in the old red sandstone of the Orcadian Basin
The present state of knowledge on the nature of the biota of the Old Red Sandstone of the Orcadian Basin is presented: current theories on the autecology of the fauna and flora known from this area and from comparable areas of similar age are discussed. The findings of extensive field work throughout the area of the Old Red Sandstone Orcadian Basin have led to a reappraisal of the nature and diversity of the ichnofauna of this area. The systematics of the diverse ichnofauna are reviewed and formal descriptions of all ichnospecies identified are presented, and autecological interpretations have been proposed for all ichnospecies. Working from the evidence of autochthonous associations of ichnofossil producing animals, an attempt was made to integrate this information with that supplied by the body fossil record to provide an approximation to natural ecological communities. The conclusions of this approach are that there were probably five, broadly environmentally controlled 'communities' in existence in Old Red Sandstone terrestrial environments; these occurring within two ecosystems: an aquatic and a terrestrial.