Trends in diversity, frequency and complexity of graphoglyptid trace fossils: evolutionary and palaeoenvironmental aspects
Graphoglyptids, a characteristic component of the Nereites ichnofacies, are patterned, mainly meander-, star-, and net-shaped trace fossils, which reveal complex burrow systems used most likely for trapping of meiobenthos or cultivation of microbes in oligotrophic deep-sea environments. They show considerable changes of diversity, frequency and adaptive radiation through Phanerozoic. Rapid radiation and increase of their diversity and density in the Late Cretaceous, probably in the Turonian, is correlated with large-scale biotic changes in marine environments, which are rooted in palaeogeographic and palaeoclimatic changes. The changes of graphoglyptids have been distinctly caused by most of the major biotic crises, especially in the Cretaceous and Cenozoic. Graphoglyptids also display an increase of complexity, which accelerated in the Late Cretaceous, when the farming activity of their trace makers became more common. The distinct changes in development of graphoglyptids challenge the time-stability hypothesis for explanation of their evolution.