Experimental attachment of sediment particles to invertebrate eggs and the preservation of soft-bodied fossils

Abstract

Clay minerals can be an important agent in the fossilization of soft tissues, notably in the Ordovician Soom Shale of South Africa and the Cambrian Burgess Shale of Canada. The replication of morphology has been attributed to adsorption of pre-existing clay minerals, or direct precipitation of authigenic clays onto tissues. Attachment of quartz and kaolinite to the surface of lobster eggs demonstrates experimentally for the first time that soft tissues could fossilize in pre-existing minerals. However, the eggs became coated only in the presence of metabolizing bacteria. This experimental approach could be used to explore why Burgess Shale-type preservation declined after the mid-Cambrian.

Sediment Effects on the Preservation of Burgess Shale-Type Compression Fossils

“…At the same time, however, this actualistic approach adds significant new levels of diagenetic and logistic complexity, not least of which involves the challenge of recovering quantitative data from sediment-bound residues while also monitoring the qualitative effects of sediment on carcass morphology (cf. Plotnick 1986;Allison 1988;Martin et al 2004;Darroch et al 2012). The compounding diagenetic feedbacks between carcasses and sedimentary matrix also make it difficult to resolve underlying mechanisms, though our experimental results introduce some intriguing possibilities.…”

“…Despite reports of accelerated carcass decay associated with some sediments (e.g., Plotnick 1986;Allison 1988;Briggs and Kear 1993), most models for BST preservation invoke mineralspecific diagenesis as an essential factor, either by suppressing normal enzyme-microbial-based decay processes (e.g., Butterfield 1990Butterfield , 1995Gaines et al 2005Gaines et al , 2012 or secondarily by enhancing the recalcitrance of relatively labile substrates (e.g., Orr et al 1998;Petrovich 2001). Surprisingly, there has been little attempt to test these various models, though Martin et al (2004) have shown that sedimentary particles will adhere to lobster eggs in the presence of bacteria, and Naimark et al (2013) have documented substantially enhanced preservation of Artemia when they are buried in kaolinite. In this study we adapt the seminal, sediment-free decay experiments of Kear (1993, 1994a) to investigate the effect of sediment mineralogy on the decay and early diagenesis of two ''model'' nonbiomineralizing marine invertebrates: Nereis virens (polychaete annelids with collagenous cuticle, sclerotized collagenous jaws, and sclerotized chitinous chaetae) and Crangon crangon (crustacean arthropods with variably sclerotized chitinous cuticle).…”

Soft‐Bodied Fossils Are Not Simply Rotten Carcasses – Toward a Holistic Understanding of Exceptional Fossil Preservation

“…[53] Microbial activity promotes decay, destroying morphological information in soft tissues, but it is also essential to establishing the conditions that lead to the replication of soft tissues in authigenic minerals. [11,[84][85][86] The nature of microbial controls is subtle and poorly understood. For example, different species of the same genus of bacteria have been shown to degrade soft tissue on the one hand and replicate cellular organization and morphology on the other, providing a potential pathway for mineral replication of soft tissue features.…”

The late Ordovician Soom Shale Lagerstätte: an extraordinary post-glacial fossil and sedimentary record

“…Urrutia & Beveridge 1994;Fiore et al 2011). Furthermore, clay minerals are seen to attach to lobster eggs in decay experiments (Martin et al 2004). More work is required to determine precisely the nature of the clays in the Soom Shale.…”