The weird and wonderful of the Ediacaran Period (Part 3): Dickinsonia – the iconic quilt-like organism of the Ediacaran

Jon Trevelyan (UK)

This is the third of my series of short articles on fossils of the Ediacaran Period. Dickinsonia is one of the most recognisable and debated organisms of the Ediacaran Period, living between 558 and 550 million years ago on shallow seafloors long before the rise of animals with hard parts.

Its flat, quilted body plan, radial-bilateral symmetry, and unusual mode of growth have placed it at the centre of discussions about early multicellular life. Was it an animal, a fungus, a giant protist (a diverse group of eukaryotic organisms that are not animals, plants or fung) or something entirely unique? Although its affinities remain contested, Dickinsonia provides a remarkable window into the ecology and complexity of the Earth’s earliest macroscopic life.

Discovery and appearance

Dickinsonia was first described in the 1940s from the fossil-rich Ediacara Hills of South Australia, preserved as shallow impressions in fine-grained sandstone. Since then, superb specimens have been found in Russia, Ukraine and India, reflecting a broad distribution across late Precambrian seafloors.

The organism had a distinctive, flat, oval body usually a few centimetres long, although some species reached over a metre. Its most striking feature is its segmented, rib-like units, sometimes called “quilted modules”, arranged around a central axial zone. These segments broaden gently toward the outer margin, giving Dickinsonia its characteristic mattress-like appearance.

The body displays bilateral symmetry, although not perfectly: the two sides are not mirror images, but offset – a feature called “glide reflection symmetry”. This unusual pattern has fuelled both evolutionary interpretations and debates about whether it truly represents an early form of animal organisation.

Interpretation and classification

The classification of Dickinsonia has been one of the great debates in Precambrian palaeontology. Proposed affinities include:

• a giant protist, similar to modern xenophyophores (giant, single-celled organisms found in the deep sea and among the largest known cells);
• a lichen or fungus-like form, living on microbial mats;
• a tiny, flat, soft-bodied creature with a very simple body plan (similar to a placozoan); and
• a stem-group bilaterian, perhaps one of the earliest animals with true tissues.

Recent chemical analyses showing the presence of cholesterol molecules in fossils from the White Sea of northwest Russia strongly support an animal affinity, although the exact position remains uncertain. If indeed an early animal, Dickinsonia may occupy a place near the base of the bilaterian lineage, representing an important stage in the development of organised tissues and directional movement.

The growth pattern of Dickinsonia is also revealing. Fossils show that new segments were added at one end of the body while older segments expanded, a form of growth consistent with animals rather than fungi or protists.

Lifestyle and ecology

Dickinsonia lived on shallow marine seafloors, crawling slowly across microbial mats that carpeted the sediment surface. Many fossils are associated with feeding traces, where the microbial mat has been stripped away beneath the organism. These “death masks” suggest that Dickinsonia absorbed nutrients directly through its underside, perhaps in a manner similar to modern placozoans.

It probably moved very slowly, either by making gentle rippling contractions or by using tiny hair-like fibres to glide across the surface. The organism likely occupied low-energy environments where microbial mats were abundant, forming part of a wider Ediacaran community of frondose organisms, soft-bodied mat grazers, and enigmatic sessile forms.

Significance

Dickinsonia is a pivotal taxon for understanding the transition from the microbial world of the Precambrian to the more dynamic ecosystems of the Cambrian Explosion. Whether or not it is a true bilaterian, it demonstrates that large, structured, mobile organisms had already evolved before animals with hard skeletons appear in the fossil record.

Its widespread distribution, distinctive morphology and strong ecological association with microbial mats make it central to reconstructions of Ediacaran seafloor communities. Moreover, its chemical signature has provided some of the best evidence yet that animals emerged before the Cambrian.

Conclusion

Dickinsonia remains one of the defining creatures of the Ediacaran world: flat, quilted and deeply enigmatic. Whether an early animal or a member of a long-lost branch of life, it represents a major step towards larger, more complex organisms. In its patterned body and subtle traces on ancient microbial mats, Dickinsonia offers one of the clearest glimpses into life before animals came to dominate Earth’s ecosystems.