Exceptional Preservation of Fossil Soft Tissues

Exceptionally preserved soft tissues yield much more information about ancient organisms than skeletal remains alone. These fossils are rare, because, generally, the postmortem processes of decay rapidly strip away information from a carcass before preservation can occur. However, if certain environmental conditions are present that slow the normal recycling of organic material, there is a possibility that soft tissues can become geologically stabilised by the processes of mineralisation or maturation. In order to understand the biological, environmental, and geological factors that control soft tissue preservation, palaeobiologists combine the study of fossil material with laboratory experiments that decay organisms in strictly controlled environmental conditions. These experimental investigations have enhanced our understanding of the inherent biases of the fossil record, and allow more accurate reconstructions of ancient organisms and a better understanding of evolution and ecology. New techniques and cutting-edge analytical equipment are revolutionising the field, opening up exciting new avenues of palaeontological research such as the identification of fossilised pigments and palaeoproteins. Key Concepts Fossils that have soft tissues generally provide more information about ancient organisms than skeletal remains alone. Organisms undergo varying amounts of decay prior to preservation. Conservation-Lagerstätten are sites where depositional environmental conditions disrupted the normal rapid recycling of organic material (e.g. decay) allowing soft tissues to preserve. Conservation-Lagerstätten are important not only because they preserve soft-bodied organisms that are extremely rare in the fossil record but also because they tend to preserve a great diversity of organisms, making them vital windows into the ancient past. Many sedimentary Conservation-Lagerstätten share characteristics of rapid burial, low oxygen, and the early onset of diagenetic processes such as mineralisation and/or maturation. Another type of Conservation-Lagerstätten are natural traps, such as amber or permafrost, but comparatively, these are geologically young. The study of burial and preservation is termed taphonomy. Since the 1980s, laboratory experiments have been undertaken to understand the drivers of soft-tissue preservation. Rather than recreating fossils or ancient environments in the lab, robust taphonomic experiments investigate the effect of discrete variables on taphonomic processes. New avenues in taphonomic investigation are opening up with the advent of new technology and laboratory equipment.