Dickinsonia

Long ago, a strange animal lived in the sea.

It was shaped like an egg. Its body had many lines on it. These lines look like ribs. It lived on the sandy sea floor. It ate tiny mats of life on the bottom.

This animal could grow very large. It could even grow to be one meter long. Some were very small too. It is fun to see its shape in rocks.

Dickinsonia was a strange creature from a long time ago.

It lived in shallow seas. We find its fossils in Australia, China, Russia, and Ukraine.

Its body was shaped like an egg. It had many segments, which are parts that repeat along the body. These segments look like ribs. Some scientists think the parts were perfectly even on both sides. Others think they were slightly offset. This is called glide reflection.

Dickinsonia did not have a mouth or a gut. Instead, it lived on the seafloor. It ate microbial mats, which are thick layers of tiny life. It may have used mucus to stick to the sand.

As it grew, it added new segments to its body. It could grow to be over one meter long. Some fossils show it could even fix itself if it was damaged. Most experts think it was a stem-bilaterian. This means it was an early type of animal with a left and right side.

Dickinsonia was a very strange living thing from a long time ago. It lived during the Ediacaran period in shallow ocean waters. We find its fossils in places like Australia, China, Russia, and Ukraine.

These fossils help us understand life on Earth before most modern animals existed. Scientists are still debating exactly what kind of creature it was. Some thought it was a jellyfish or even a lichen. Today, most experts think it was an early animal.

Its body was shaped like an oval or an egg. The body had many segments that looked like ribs. These segments grew wider toward one end of the creature. Dickinsonia grew by adding new pairs of segments to its body. It likely had no maximum size, which is called indeterminate growth.

It may have even been able to fix itself if it was hurt. This process is called regeneration. It lived on the seafloor and ate microbial mats. These mats were thick layers of tiny life on the seabed. It may have used mucus to stick to the sand.

Reg Sprigg first found these fossils in 1946. He found them in the Flinders Ranges of South Australia. He named the creature after a man named Ben Dickinson.

In the beginning, Sprigg thought it was a jellyfish. He thought the grooves were part of a canal system. Later, scientists thought it might be a type of worm. In 1985, researchers created a new group called Proarticulata for it. This group included other segmented creatures like Vendia and Spriggina. Many ideas about its family have changed over the years.

Dickinsonia fossils are usually found as imprints in sandstone. These imprints are negative shapes left in the rock. They formed when sand covered the body before it decayed. The sand sometimes hardened into a "death mask" around the body.

Some specimens are very small, only a few millimeters long. Other fossils are huge and reach over one meter in length. We find many of them at Nilpena Ediacara National Park. In this park, hundreds of fossils are preserved in the ground. Some fossils look stretched because they were moved by sand flows.

It is hard to know exactly how Dickinsonia fits into nature. Most biologists think it was a stem-bilaterian. A bilaterian is an animal with a clear left and right side. Dickinsonia had a midline, but it lacked a mouth or a gut. This makes it different from most animals we see today.

In 2018, scientists found cholesterol in some Russian fossils. Cholesterol is a substance only made by animals. This discovery gave more evidence that Dickinsonia was an animal. Even so, scientists still argue about these findings today.

Dickinsonia is a genus of extinct organisms that lived during the late Ediacaran period. These creatures lived in shallow marine environments across what are now Australia, China, Russia, and Ukraine. They are significant because they belong to the Ediacaran biota, a group of early life forms. Scientists study them to understand how complex life began on Earth. While their exact identity is still a major debate, they represent a fascinating chapter in biological history.

The body of a Dickinsonia was roughly oval or egg-shaped. It featured many segments that looked like ribs running along its surface. These segments grew wider as they moved toward the wider end of the body. A midline ridge or groove divided the body into two sides. One end had a single, unpaired segment called the anterior most unit. This unit likely represented the front of the organism. Researchers debate if the segments showed true bilateral symmetry. Bilateral symmetry means the left and right sides are mirror images. Alternatively, they might have used glide reflection, where segments are slightly offset.

Dickinsonia grew in a very specific way throughout its life. It grew by adding new pairs of segments at the end opposite its front unit. This process is known as indeterminate growth, meaning it had no set maximum size. However, the addition of new segments likely slowed down as the organism got larger. Some fossils from Russia show branched internal structures within the body. The body was likely sack-like and made of a resistant, unmineralized material. Evidence suggests that damaged individuals could undergo regeneration to fix themselves. This means they could regrow parts that were lost or broken.

These organisms were mobile and lived on the seafloor. They likely fed by consuming microbial mats, which are thick layers of tiny life on the seabed. They may have used structures on their underside to eat these mats. Some scientists believe they used mucus to temporarily stick to the seafloor. This might have helped them stay in place in very shallow water. We can see evidence of this behavior through trace fossils. These are marks left in the sediment, sometimes found in chains. These specific feeding impressions have been assigned to the genus Epibaion.

Discovery of Dickinsonia began in 1946 in South Australia. Reg Sprigg described the organism in 1947 and named it after Ben Dickinson. Initially, Sprigg thought it was a jellyfish-like creature. He believed the grooves were part of a canal system. Over time, scientific views shifted many times. In 1985, researchers proposed a new phylum called Proarticulata. This group included Dickinsonia and other segmented forms like Vendia and Spriggina. In 2013, one researcher suggested they were lichens, but most scientists rejected this. They believe the marine environment fits the evidence much better.

Fossils of Dickinsonia are preserved as imprints in sandstone beds. These are called negative impressions because they show the shape of the upper side of the organism. They formed when sand covered the body before it fully decayed. The sand then underwent cementation to turn into rock. This might have happened through carbonate cementation or pyrite death masks. Some fossils are tiny, only a fraction of a millimeter thick. Others are much larger, reaching over one meter in length. In Nilpena Ediacara National Park, hundreds of specimens are preserved together. Some look stretched because they were moved by sand flows.

Today, most biologists classify Dickinsonia as a stem-bilaterian. A bilaterian is an animal with a distinct left and right side. This classification is supported by its predictable growth and clear axis. However, Dickinsonia lacked a mouth, an anus, and a gut tract. This makes it different from most modern animals. In 2018, researchers found cholesterol in Russian specimens. Since cholesterol is only produced by animals, this supported the animal theory. Even with this evidence, the scientific community continues to discuss its exact place in the tree of life.