Preservation and bias in the Cambrian fossil record

Abstract

Paleontology views deep time ecosystems through a taphonomic lens, biased and restricted by the controls enacted on each fossil deposit by various environmental factors, and including chemical and biological variables. Human-induced bias has recently been acknowledged as an additional layer of complexity, contributing further inconsistencies of our understanding of metazoan diversity in deep time. The Cambrian Haiyan Lagerstatte of Yunnan, China, examined in Chapter 2, preserves an exceptionally diverse biota, with many of its soft-bodied and biomineralized organisms being preserved via pervasive pyritization with associated carbon films. The exceptional pyritization of many soft-bodied organisms--which otherwise may not have been preserved--shows that this ecosystem is an exceptional repository of Cambrian biodiversity, but there remains uncertainty in the regional application of this mode of preservation. On the other hand, the biotas of the Marjum, Wheeler, Weeks formations and Spence Shale Lagerstatte of the western U.S. show significant discrepancies in the diversity of each deposit when the published taxonomic record of these Lagerstatten is compared to the taxonomic record of those formations deposited in publicly available collections. As detailed in Chapter 1, this shows that, while the diversity of deep time ecosystems may be conserved and well-represented in some cases, the published representation of those ecosystems is inherently flawed.

The Evolution of Mineral Hardness Reveals Both Changing Parageneses and Preservational Bias in the Mineralogical Record

“…Preservational and anthropogenic biases in the mineralogical record have received relatively minimal attention. However, important concepts and approaches have been devised by the paleobiological community, notably in their research on ancient ecosystems [18][19][20][21][22][23]. A brief survey of this paleobiological literature is, thus, informative.…”

“…In addition to these inevitable physically and chemically induced losses in the fossil record, a number of potentially avoidable anthropogenic biases exist (e.g., [22,45], and the references therein). Among the many pitfalls that may contribute to non-random collections in the field are the tendency to avoid large and bulky specimens, the difficulty in extracting specimens from the hardest lithologies, and the challenge in identifying and collecting microscopic species [34,37,[46][47][48].…”