Taphonomic biases in the insect fossil record: Inconsistent preservation over geologic time
Insect taphonomy is a topic that has drawn interest because of its potential biases on diversity and ecological information recorded by ancient insect faunas. To be preserved as a compression fossil, insects must be transported from their original habitat, break water surface tension and sink, and avoid degradation and predation while in the water column and prior to burial. We assembled a database of more than 6400 Carboniferous-Pliocene insect compression fossils from the primary literature to test biotic and environmental controls on preservation quality. We grouped the fossils into 10 Myr bins and scored preservation quality as either articulated bodies or isolated wings; specimens with a body implied higher quality of preservation. Paleozoic and Triassic insect fossils are known overwhelmingly from isolated wings (only 20% articulated bodies), but our database shows a significant increase in the percentage of specimens preserved as articulated bodies beginning in the Late Jurassic, about 160 Myr ago. This transition could reflect variations in the robustness of different insect orders and shifts in the taxonomic composition of insect faunas, but all the major groups in the database exhibit significant increases in articulation. Instead, a shift in the frequency of insects preserved in different paleoenvironments could explain the trend. Lacustrine, especially large lake, sediments contain a greater proportion of articulated bodies. The change in the paleoenvironment of where insects are preserved is the most important factor in explaining the increase in articulation of insect fossils.