Treptichnids, T. pedum, and the evolution of behavioral complexity over the Ediacaran-Cambrian boundary

• Applicant: Dr. Simon Darroch, Ph.D.
• Subject Area: Palaeontology ; Geology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 558639296

The base of the Cambrian Period (538 million years ago) is a crucial stratigraphic boundary in the geological record, marking the base of the Phanerozoic Eon. Identifying this boundary in the field and correlating it across different basins and cratons has, however, historically proven difficult. The overarching goal of this project is to develop and refine biostratigraphic criteria for recognizing the Ediacaran-Cambrian boundary (‘ECB’) in fossiliferous sections, and aid in worldwide dating and correlation. Biostratigraphically, the ECB is defined using the first occurrence datum of Treptichnus pedum. T. pedum is a trace fossil that records the movement of a bilaterian metazoan, and represents the oldest example of bed-penetrative burrowing in the fossil record. Using a combination of specimen-based morphological analysis, exploratory fieldwork, and neoichnological experiments, this project aims to answer longstanding questions surrounding this trace fossil. First, is T. pedum morphologically unique (and thus easy to identify), or does it represent part of a spectrum of similar (‘treptichnid’) trace fossils that emerge earlier in the late Ediacaran? How does the ‘complexity’ of treptichnid trace fossils change through the Ediacaran and Cambrian? What is the identity of the treptichnid tracemaker(s)? What ecological behaviors do different burrow morphologies represent? And, how did these evolving behaviors alter the marine sedimentary environment over the Ediacaran-Cambrian transition? The answers to these questions will allow us to realize three specific goals: 1) establish robust criteria for recognizing T. pedum in the field; 2) quantify rates and patterns of evolving behavioral complexity through the Cambrian explosion; and, 3) determine the stratigraphic position of the Cambrian boundary in the Nama Group of southern Namibia. By achieving these goals, we will form direct links between trace fossils, the evolutionary events of the Cambrian explosion, and constrain the stratigraphic position and age of the ECB in the best-exposed sequence of Ediacaran-Cambrian sediments anywhere in the world.

• DFG Programme: Research Grants