Chirotherium and its domain: a description of rediscovered specimens from northwest England

Abstract

A rediscovered collection of tetrapod footprints originating from Storeton, Merseyside (and lodged in the stores of the Museum of Lancashire) is described. Chirotheroid footprints are identified using the guidelines outlined by King (1997) and compared to descriptions of accepted ichnospecies (King et al. 2005). The Rossendale Collection contains some well preserved but isolated sets of Chirotherium storetonense. A unique trackway specimen containing Chirotherium storetonense, Chirotherium barthii, small rhynchosaur footprints, and an example of Equisetites keuperina is described for the first time. The lithology of the Helsby Sandstone at Storeton and the Tarporley Siltstone at Lymm is described in thin section and compared with previous lithological research based on hand specimens. Specimens from Lymm display rhombic crystals (possibly gypsum) while those from Storeton exhibit staining by iron oxides. The theory of deciphering the locality of specimens with unknown origins is tested by comparing thin section analysis. These results are used to bolster the understanding of the stratigraphy at Storeton and Lymm. The Museum of Lancashire's Storeton specimens display a paler lithology to other collections and could have originated from a slightly different locality. The variety of fossil evidence present in the rediscovered Rossendale Collection is interpreted in conjunction with the thin section analysis and compared with previous palaeoecological research. The presence of muscovite in both the Helsby Sandstone and the Tarporley Siltstone indicates fluvial deposition. Due to the superposition of fossils, the Chirotherium producer, rhynchosaurs, and vegetation (such as Equisetites keuperina) are confirmed as existing at the same time.