Outline of a Permian tetrapod footprint ichnostratigraphy
Tetrapod footprints are among the most common fossil remains in continental Permian strata and thus are of biostratigraphic interest. Based on the vertical distribution of the 13 best-known Permian tetrapod ichnotaxa, three footprint biochrons are suggested for the period: (1) Dromopus – latest Carboniferous (approximately Gzhelian) to late Early Permian (approximately Artinskian), representing ichnoassemblages dominated by tracks of temnospondyls, reptiliomorphs, pelycosaurs and early diapsids; (2) Erpetopus – late Early Permian (approximately Kungurian) to late Middle Permian (approximately Capitanian), representing ichnoassemblages dominated by tracks of non-diapsid eureptiles; and (3) Paradoxichnium – Late Permian (Wuchiapingian and Changhsingian), representing ichnoassemblages dominated by tracks of medium- and large-sized parareptiles, non-diapsid eureptiles and early saurians. This is the most conservative ichnostratigraphic concept, and it may be possible to refine it to almost stage-level resolution by future comprehensive analysis, especially of Permian captorhinomorph and therapsid footprints. Other major tasks to improve Permian tetrapod footprint ichnostratigraphy include enhanced knowledge of Middle Permian tetrapod footprints, and clarification of the palaeoenvironmental factors that may control the distribution of tetrapod footprints in space and time.
Figures & Tables
The Palaeozoic Era ends with the c. 47-million-year-long Permian Period. This was a major juncture in Earth history when the vast Pangean supercontinent continued its assembly and the global biota suffered the most extensive biotic decimation of the Phanerozoic, the end-Permian mass extinction. It was also the time of accumulation of vast mineral and energy deposits, notably of salt and petroleum. The temporal ordering of geological and biotic events during Permian time is, therefore, critical to the interpretation of some unique and pivotal events in Earth history. This temporal ordering is based mostly on the Permian timescale, which has been developed and refined for nearly two centuries. This book reviews the history of the development of the Permian chronostratigraphic scale. It also includes comprehensive analyses of Permian radioisotopic ages, magnetostratigraphy, isotope-based correlations, and timescale-relevant marine and non-marine biostratigraphy and biochronology.