Life and Environment in the Basin 250/225 Ma Talk By Dr. David Thompson on 12 Feb. 2003

David’s talk traced the historical background to the discovery tail was carried above the ground. It was not until 1960s that and interpretation of body and trace fossils in terms of Krebs in Switzerland found a whole skeleton, Ticinosuchus, palaeoenvironmental reconstructions. and Soergel's findings were confirmed. About the same time a schoolboy, Geoffrey was finding water fleas at The Permo-Triassic Cheshire Basin overlies the Alderley Edge which later study confirmed lived in fresh or Carboniferous basin with Sherwood Sandstone lying over brackish water only and in a continental environment. At Permian sandstone, topped with Mercian mudstone and Styal fossil insect remains were found reinforcing the arid some Jurassic. The area includes the Wirral, Liverpool, and fresh brackish water conditions, possibly with small Daresbury, , Tarporley, Styal, , the Alderley shallow lakes. When Speke Airport runway was being area, Alton, parts of Staffordshire and down to Grinshill. The extended in the mid 1970s a quarry was opened revealing rocks we are interested in, largely around the Grinshill area, the upper Tarporley siltstone formation with Chirotherium are the aeolian beds with a sea incursion before the mass footprints and many invertebrate trace fossils; extinction. Also the aeolian series, a very large erosive Thalassinoides, crustaceans sub-tidal and intertidal; surface, fluvial beds followed by more aeolian beds, possibly brachiopods, worms and arthropods mud and sand flats, more unconformities in the Wilmslow sandstone then more facies sharing some characteristics with Tarporley fluvial and aeolian beds alternate in the Helsby sandstone sandstones at Grinshill. About the same time Dr. John Stanley and Grinshill flagstone. A change then occurs in and Dr. Thompson working on the Grinshill Flagstones sedimentation, above thin bedded and at the top of the found footprints and sedimentary structures of animals Grinshill quarries, there are some red mudstones. In other apparently shuffling around possibly feeding like sheep. places salt beds follow and further mudstones. The base of the basin is at about 280ma, the marine fill 250ma and just Ending in 1990 Mike Benton, as referred to earlier, gathered after the unconformity. together 18 specimens including 8 heads, from a number of museums, of Rhynchosaurus articeps. He interpreted and The fossils, both body and trace, started to be found 1824 in described them as herbivores with large guts for digesting a period of initial excitement in a quarry at Dumfries. These vegetable matter, similar to Uromastics of the semi arid areas were casts of footprint tracks which were shown to Rev. in N. Africa today. Their jaws worked like folding penknives Duncan, who involved Rev. Dr. William Buckland. There to chop up the vegetation known as the Dicroidium flora. He were finds also at Tarporley and near Liverpool. All these illustrated that the animals feet could make the footprints that footprints were of four forward pointing toes and one have been found in abundance. backward and regarded as made by Chirotherium. Alongside some of the tracks were fossils of the horsetail In 1997 Mike King & Dr. Thompson investigated in an area of plant, Dicroidium. Dr. Buckland was sent material from Hilbre Island, the footprint tracks of Chirotheroids in three Grinshill via Dr. Thomas Ogier Ward by canal. Dr. Buckland horizons and found many rhynchosauroid footprints at four used animals from his menagerie in attempts to interpret the horizons within a vertical metre of each other. All were likely footprints. Murchison was also involved in these studies at to have been made in temporary muddy pools made in a the Geol. Soc. in London, no doubt influencing Darwin, as braided river environment. Mike King also re-investigated secretary of the Society, after his return from the Beagle three Chirotheroid specimens found in the 1890s and voyage. identified them as Isochritherium, a herbivore and Brachychirotherium, an omnivore, both 4 metres long. With During this period, 1837-1840, bones had been found, but David Thompson he measured a large slab in a quarry these were not properly described until Mike Benton owner’s garden and they described the tracks as from examined them in 1990 and described them as from Rotodactylus, best known from remains in Argentina. The Rhynchosaurus, a small reptile. The last skull of a association and orientation of Chirotherium and Rhynchosaurus was found at Grinshill in 1859. Various finds Rhynchosaurus tracks suggested that the former were eating of footprints, bones and teeth had been found in the Liverpool the latter. area, Warwickshire, and Shropshire, up until the First World War, then there was a period of neglect, except on the Dr.Thompson brought to the meeting a large number of rocks continent. All this time interpretation of the tracks and illustrating the ripple marks and structures found in the footprints, with the odd position of the backward toe or spur, Cheshire Basin. was causing problems of gait, and the single tooth, with lamellae led people to think in terms of amphibians. In Les Dolomore Germany, Soergel, in 1925, found abundant tracks and realised that the spur was more like a little finger and that the