Research Interests
I have research interests across the entire Neoproterozoic to Cambrian biological transition, but most of my previous work has focused on the palaeontology, taphonomy (preservation), and palaeoecology of the late Ediacaran Period, roughly 580 to 539 million years ago. My group combines study of fossils, minerals, sedimentary rocks and geochemical records from this interval to determine the links between Ediacaran environments and their organisms. Prominent research areas include:
The evolution of locomotion across the Ediacaran - Cambrian boundary
Trace fossils (fossilized impressions resulting from the behaviour of an organism) are a remarkable resource for palaeontologists. Most trace fossils are interpreted to have been produced by animals with muscular tissue, and so recent discoveries of Ediacaran-Cambrian trace fossils appear to constrain the evolution of mobile, muscular animals to a short interval towards the end of the Ediacaran Period.
Simple surface traces from sites in Russia, China and Australia can be common, but are restricted to shallow marine settings, and are all younger than about 560 Ma. During my PhD I documented an assemblage of horizontal surface traces in rocks from Mistaken Point Ecological Reserve, Newfoundland. These traces are dated to ~565 Ma, and occur in deep-marine depositional environments, providing some of the oldest evidence for mobile animals in the fossil record (Liu et al. 2010; Liu et al. 2014). More recent work has explored the wider Ediacaran trace fossil record (e.g. Liu & McIlroy 2015); the meiofaunal (organisms smaller than 1mm) record of bilaterian burrowing activity (Parry et al. 2017); and interrogation of evidence for complex burrowing later in the Ediacaran (Psarras et al. 2023). |
Taphonomy in the Ediacaran Period - explaining exceptional preservation
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Ediacaran macro-organisms are commonly interpreted to have been preserved as simple impressions in siliciclastic sediments. Such preservation of soft-bodied organisms is rare in the Phanerozoic, and so the abundant and often exquisite preservation of non-mineralized organisms in the Ediacaran Period requires explanation.
My work investigates the interplay between the physical and chemical properties of the sedimentary substrate, microbial communities, and carcasses in the production of Ediacaran fossil impressions (e.g. Brasier et al. 2013; Menon et al. 2016), and more widely throughout the geological column (Brasier et al. 2010; Davies et al. 2016). My colleagues and I have demonstrated that the formation of a pyritic veneer, most likely via bacterial sulfate reduction, plays a key role in Ediacaran soft-tissue preservation in Newfoundland and Australia (Liu et al., 2019), and that burial of this pyrite may have had a significant impact on global marine oxygen concentrations (Liu 2016). I have also contributed to collaborative work to explore modern controls on the quality of Ediacaran fossil preservation (e.g. Matthews et al. 2017). I am also interested in indentifying 'taphomorphs' amongst the Ediacaran biota. Collaborative work in 2011 recognised a taphonomic spectrum from well- to poorly-preserved specimens of Ediacaran fossils on individual bedding planes. We interpreted this to result from temporal differences in the degree of decay that carcasses had undergone prior to burial (Liu et al. 2011). Our taphomorph hypothesis proposed widespread time-averaging within Ediacaran palaeocommunities, and has led to subsequent work into community succession (Liu et al. 2012) and assemblage palaeoecology (Liu et al. 2015). |
Ediacaran taxonomy, growth, reproduction, and new discoveries
I am involved in several different projects exploring the metabolic and reproductive pathways utilized by the Ediacaran biota (e.g. Mitchell et al. 2015), their broader macroecology (Mitchell et al., 2019), and their developmental biology (Dunn et al. 2018). Such work has been made possible by recent discoveries of specimens of juvenile organisms (e.g. Liu et al. 2012), which enable reconstruction of growth trajectories in individual taxa, and by the application of laser scanning techniques, pioneered by my colleague Dr Emily Mitchell.
Discoveries of new taxa (e.g. Liu et al. 2014, Haootia) and new fossil localities (e.g. Liu et al. 2016; Liu & Tindal 2020), along with detailed studies of individual taxa (e.g. Orbisiana and Arborea; Kolesnikov et al. 2018; Dunn et al. 2019), are contributing to recognition that late Ediacaran marine ecosystems housed complex and diverse communities containing representatives of multiple biological groups, including early animals (Dunn et al., 2021). Most recently, the finding that many Ediacaran frondose fossils are connected to one another by filamentous threads (Liu and Dunn 2020) has opened a new field of inquiry to determine the role of these structures in the life cycles of these organisms. I am also involved in larger projects attempting to integrate fossil data with geochemical and geochronological information from other sites (e.g. the UK/China-funded BETR programme; Matthews et al., 2020), and am keen to promote consideration of the Ediacaran fossil record in the context of a broader Ediacaran to Cambrian transition (Wood et al. 2019). Current work investigates newly discovered fossil sites in southern Namibia, and Shropshire (UK). |