Dickinsonia

Dickinsonia

Dickinsonia is a genus of extinct organism from the late Ediacaran period. It lived in places that are now Australia, China, Russia, and Ukraine.

Dickinsonia had a round body with many segments. It could be very small or very large — from just a few millimeters to over a meter long. It probably lived in shallow water and ate microbial mats.

Dickinsonia was part of the Ediacaran biota. Scientists are not sure exactly what it was related to. It was once thought to be a jellyfish. Other ideas were that it was a land-dwelling lichen, a placozoan, or a big protist. Today, many think it was a sea animal, maybe an early stem group bilaterian.

Dickinsonia looks similar to other segmented organisms like Vendia, Yorgia, and Spriggina. Some think it belonged to the group Proarticulata or the Dickinsoniomorpha group. Scientists still debate whether the segments of Dickinsonia were bilaterally symmetric or offset in a certain way, or perhaps both.

Description

Dickinsonia fossils are found only as imprints and casts in sandstone. These fossils can be very small, from just a few millimeters, or as large as about 1.4 meters (4 feet 7 inches). They have a body that is nearly symmetrical, segmented, and either round or oval shaped, a bit wider at one end. The segments are arranged in a special way, and scientists are still discussing exactly how they were placed on the organism.

Dickinsonia’s body is thought to have been sack-like, with a tough outer layer. Some fossils show internal structures, and it is believed that Dickinsonia grew by adding new segments at one end. It likely kept growing and could fix itself if it got damaged.

Ecology

Dickinsonia likely moved along the ocean floor. It probably fed on tiny life on the sea bottom using parts on its underside. Scientists have found marks in the sand that look like Dickinsonia, showing how it may have fed. A study from 2022 thinks Dickinsonia might have stuck to the sand using a slimy substance, helping it live in very shallow water.

Taphonomy

Fossils of Dickinsonia are found as imprints on the bottom of sandstone layers. These imprints show the top sides of the creatures that were buried by sand. The sand hardened before the creatures broke down, keeping their shapes. Sometimes, these imprints are squished or stretched.

Very rarely, Dickinsonia fossils are found as solid shapes in big sandstone chunks. These are often found together with other ancient creatures like Pteridinium, Rangea, and others. Large groups of Dickinsonia fossils are preserved in Nilpena Ediacara National Park, where park rangers lead tours during cooler months. These fossils show what happened when creatures were moved from the sea floor by sand flows. One of these unusual fossils was once thought to be a different type of creature but was later identified as Dickinsonia.

Taxonomy

History

Dickinsonia was first found in 1946 in the Flinders Ranges in South Australia. It was named after Ben Dickinson, who was the Director of Mines for South Australia at the time. More examples of Dickinsonia have been discovered in Ukraine, Russia, and China.

At first, scientists thought Dickinsonia might have been a jellyfish-like creature from very early times. Over the years, many ideas about what Dickinsonia was have been suggested. Some thought it might be related to animals with segmented bodies, while others proposed different groups. Recently, some scientists have suggested it might have been an early animal, but its exact place in the tree of life is still uncertain.

Modern classification

Today, many scientists believe Dickinsonia might have been an early relative of animals, but its exact classification is still debated. Some studies have found a substance called cholesterol in Russian specimens, which is usually made by animals, but this is still being discussed. Dickinsonia had clear left and right sides, suggesting it had a simple body plan, but it did not have a mouth or gut like most animals today.

Species

Since 1947, scientists have described 11 species of Dickinsonia. Currently, three are considered valid, two are still being studied, and the other six are no longer considered correct.