Arthropods are one of the most significant groups of animals through Earth history, and so it is important to determine what taphonomic processes affect their fossil record. Arthropod dominated Lagerstätten and Small Carbonaceous Fossil (SCF) assemblages are abundant throughout the Cambrian. Segmented, multipodous arthropods, as well as bivalved arthropods are present as articulated and complete carcasses and as isolated fragments in these assemblages; however, non-bivalved arthropods are only preserved as SCFs. This thesis aims to identify the effects of wave processes on the degradation of arthropods, whether or not different arthropods have different levels of robustness, and if this results in a bias towards certain arthropods being preserved as fully articulated fossils or SCFs. In taphonomic experiments, we used carcasses of the arthropods Ligia oceanica (sea slater), Triops longicaudatus (tadpole shrimp), and Branchinella thailandensis (fairy shrimp), as analogues to segmented, multipodous arthropods, bivalved arthropods, and non-bivalved arthropods respectively, and exposed them to either oscillatory wave action or static decay for up to 96 hours. In addition, we used Energy Dispersive Spectroscopy to identify the levels of mineralisation of each arthropod. An analysis of fossil arthropod specimens from the Cambrian aged Sirius Passet Lagerstätte of North Greenland was also conducted to investigate the taphonomic variation amongst specimens. We found Ligia oceanica and Triops longicaudatus may have partially mineralised exoskeletons and can withstand 48-72 hours of exposure to wave action before disarticulating and fragmenting; whilst Branchinella thailandensis had no evidence of mineralisation and began to degrade within 24 hours and fragmented into isolated remains by 48-72 hours. In the Sirius Passet Lagerstätte, we identified multiple segmented multipodous specimens and one bivalved arthropod specimen preserved in varying states of disarticulation. These results suggest that exposure to wave processes may explain why we see fossil arthropods analogous to Ligia oceanica and Triops longicaudatus regularly in both Lagerstätten and SCF deposits, whereas those analogous to Branchinella thailandensis are exclusively found in SCF deposits. The variation in mineralisation among the three modern arthropods may also explain the robustness of the carcasses and individual disarticulated and fragmented remains. Alongside the presence of disarticulated carcasses in the Sirius Passet Lagerstätte, this may suggest that the presence of disarticulated carcasses of mineralised arthropods in the fossil record actually represent a higher level of robustness, and less or non-mineralised arthropods may actually be underrepresented. This highlights the need to consider all specimens, in particular those preserved in varying taphonomic states, in key fossil assemblages such as Lagerstätten and SCFs, as well as the effects of taphonomic processes on certain groups to gain a true understanding of extinct arthropod communities.
The Experimental Effects of Wave Processes on Aquatic Arthropod Taphonomy: Implications for Interpreting the Taphonomy and Palaeoecology of Konservat Lagerstätten and Small Carbonaceous Fossils (SCFS)
Devine, L. K. (Author). 2 Dec 2025
Student thesis: Doctoral Thesis