The variations of terrestrial trace fossils and sedimentary substrates after the end‐Permian extinction in the Dengfeng area, North China

Abstract

Evolution of terrestrial infauna in the Early Triassic enables to understand terrestrial biotic recovery after the end-Permian mass extinction (EPME). Six ichnospecies in two ichnogenera, including Skolithos linearis, S. verticalis, S. annulatus, S. isp., Planolites montanus, and P. beverleyensis, were recognized from the Lower Triassic Liujiagou Formation (Induan Stage) and Heshanggou Formation (Olenekian Stage) in the Baiping section of the Dengfeng area, North China. The ichno-ecological analyses of ichno-taxonomic abundance, ichnodiversity, bioturbation index, burrow size, and tiering level revealed that terrestrial infauna expanded from epibenthic to endobenthic through the Early Triassic. The tiering deepening suggested that tracemakers gradually began to excavate into the sediments instead of moving on the microbial mats, indicating that the burrowing capability of trace-making animals has recovered in the Olenekian. Four types of sedimentary substrates were summarized: non-bioturbated matground, matground with bioturbated patches, weakly bioturbated mixed ground, and moderately bioturbated mixed ground. Occurrence of the substrate of mixed ground may be a sign of the initial recovery of the terrestrial ecosystem after the EPME.

Crayfishes from the Jehol biota

“…Due to the very limited fossil record of freshwater crayfishes, it is not possible to know if at the time crayfishes were already widespread all over Pangea or not. However, if they were not yet present in Northern China, crayfishes may have invaded this area from the rest of Pangea as early as Triassic as Cambo-rygma litonomos Hasiotis & Mitchell, 1993, ichnofossils usually attributed to crayfishes, are known from Henan Province (Zheng et al 2023), after the closure of the Ural seaway (Fokin et al 2001). Astacoidea (northern hemisphere crayfishes) and Parastacoidea (southern hemisphere crayfishes) probably diverged around the Permian-Triassic (Bracken-Grissom et al 2014) or the Middle Triassic (Wolfe et al 2019), long before the breakup of Pangea, which is dated around the Callovian (Enay et al 1993).…”