Taphonomy

Study of processes between an organism's death and observation of its remains, including transport, decay, burial and preservation. These processes bias the fossil and archaeological record.

Processes through which biological remains or traces enter the fossil record. Complete replacement by new minerals is only one possible pathway.

Preservation retaining anatomical information normally removed by decay or burial alteration. It reflects particular preservational pathways, not an unbiased sample of all life.

Erosion and redeposition of previously buried remains into a younger deposit, potentially confusing environmental and chronological interpretation.

Movement of remains by currents, waves, gravity or organisms. Sorting depends on size, density, shape and articulation rather than solely on taxon abundance.

Differential movement or deposition of remains by flowing water, dependent on their shape, density, size, orientation and articulation.

Separation of connected skeletal elements as supporting tissues fail or external forces act. An articulated skeleton need not have been buried instantly.

Transformation and loss of biological tissues after death through autolysis, microbial activity and associated processes. Decay rates differ among anatomical characters.

Enzymatic breakdown of cells by their own components after loss of normal regulation.

Processes affecting remains before final burial, including decay, disarticulation, transport and surface modification. These mechanisms can continue or recur during reworking.

Physical and chemical alteration after burial, potentially modifying fossil tissues and isotopic compositions.

Change in the crystal organization of fossil material during alteration, potentially obscuring original histological or chemical information.

precipitation or replacement by minerals during burial alteration. Early mineral formation can retain fine biological detail, while later alteration can destroy or obscure it.

Reduction of sediment volume during burial that can flatten, distort or fracture enclosed remains.

Preservation or replication by calcium phosphate minerals, sometimes retaining soft-tissue detail when precipitation occurs before its destruction.

Preservation retaining anatomical information normally lost, especially soft tissues. Such deposits reveal otherwise hidden diversity but still select particular environments and tissue types.

An exceptionally preserved early Cambrian biota from China, including Haikouichthys and Myllokunmingia.

A Cambrian fossil-bearing succession in Canada preserving diverse animal anatomy, including Metaspriggina.

Postmortem loss and alteration of tissues. Replicated observations show that loss can be anatomically selective, so a decayed specimen may look systematically less derived.^[ref]

Mixing remains produced at different times in one sampled assemblage. It can occur locally without long-distance transport, blurring short ecological events.

Erosion of an older deposit and incorporation of its fossil material into a younger one. It can create a misleading apparent last occurrence.

Movement before final burial can sort remains by size, shape and density. Articulation alone cannot prove local origin, and disarticulation alone cannot prove transport.

A collection of fossil remains associated in a specified deposit or sample. Its members may have different original habitats or ages; transport of fossil remains and time averaging affect its interpretation.

An assemblage containing remains transported from their original living sites. Hydraulic sorting can enrich durable parts or mix habitats; transport does not invariably disarticulate a carcass.

An assemblage whose organisms are preserved where they lived. Local origin does not eliminate taphonomic bias: soft tissues can disappear and resistant parts can accumulate through time.

Systematic distortion of biological information through differential preservation and recovery. teeth and delicate soft tissues need not have the same probability of entering the fossil record; even a locally buried assemblage can therefore give a biased account of its living community.

Erroneous placement toward the base of a lineage when loss of diagnostic characters through carcass decay is interpreted as an ancestral biological absence. Coding unobservable characters as unknown and comparing preservation across specimens can reduce the problem.