Exceptional fossil preservation and the cambrian explosion

Area of Science:

• Paleontology
• Evolutionary Biology
• Geology

Background:

• Exceptionally preserved, non-biomineralizing fossils are crucial for understanding the Cambrian explosion.
• Six types of exceptional preservation existed during the terminal Proterozoic-Cambrian interval, influenced by specific taphonomic conditions.
• Taphonomic pathways varied during this transition, partly due to evolutionary innovations.

Purpose of the Study:

• To analyze the relationship between taphonomic pathways and fossil expression.
• To aid in the interpretation of exceptionally preserved, often problematic, early Cambrian fossils.
• To clarify the evolutionary context of early Cambrian life forms.

Main Methods:

• Identification of six distinct types of exceptional preservation.
• Analysis of taphonomic circumstances and their spatial-temporal restrictions.
• Comparison of fossil preservation in different facies (e.g., shale).
• Interpretation of fossil structures based on preservation type (flattened vs. 3D).

Main Results:

• Flattened fossils in shale often represent degradation-resistant acellular/extracellular tissues (e.g., chaetae, cuticles).
• Three-dimensional preservation indicates labile cellular tissues that attracted early diagenetic minerals.
• Specific fossil interpretations were revised: hyolithid integument, Wiwaxia sclerites, Amiskwia integument, arthropod midgut glands, and misidentified Chengjiang arthropods.
• Putative lobopods and deuterostomes are reinterpreted as arthropods.

Conclusions:

• Understanding taphonomy is essential for accurate interpretation of early Cambrian fossils.
• Taphonomic variability influenced the fossil record of evolutionary and biogeochemical shifts.
• This research refines our understanding of early Cambrian fauna and evolutionary patterns.