Charnia is an extinct group of lifeforms from the Ediacaran biota. These organisms had frond-like shapes with ridges that looked like leaves. The ridges branched to the right and left from a zig-zag line in the center. This pattern is called glide reflection or opposite isometry. The genus Charnia was named after Charnwood Forest in Leicestershire, England, where the first fossil was found. The first species, Charnia masoni, was named after Roger Mason, a student who was thought to have found it first. Charnia is important because it was the first Precambrian fossil to be identified correctly.

The organism lived on the ocean floor about 570 to 550 million years ago. It likely absorbed nutrients from the water. Even though Charnia looked like a fern, it was not a plant or alga. This is because the fossils were found in deep water, far below the sunlight zone where photosynthesis can happen.

Diversity

Several types of Charnia were first described, but only the main species C. masoni, C. brasieri, C. ewinoni, C. gracilis, and C. grandis are considered valid. Some examples of C. masoni were originally placed in the genus Rangea or a different genus called Glaessnerina. Later, some of these were reclassified as a separate species, C. grandis.

Two other Charnia species were moved to different genera:
• Charnia wardi, described in 2003, was later placed in the genus Trepassia in 2009.
• Charnia antecedens, described in 2007, was later placed in the genus Vinlandia in 2012.

Some Ediacaran fossils are believed to represent Charnia, Charniodiscus, and other petalonamid organisms at different stages of decay. These include the ivesheadiomorphs Ivesheadia, Blackbrookia, Pseudovendia, and Shepshedia.

Distribution

Charnia masoni was first discovered in the Maplewell Group in Charnwood Forest, England. Later, it was found in the Ediacara Hills in Australia, Siberia, and the White Sea area in Russia, as well as in Precambrian rock layers in Newfoundland, Canada.

It lived approximately 570 to 550 million years ago.

Discovery

Charnia masoni was discovered by Roger Mason, a student who later became a professor of metamorphic petrology. In 1957, Mason and his friends were rock-climbing in Charnwood Forest, a protected fossil site in Central England. They found an unusual fossil, and Mason made a copy of the rock's surface. He showed the copy to his father, who was a minister and a teacher at Leicester University. His father knew Trevor Ford, a local geologist. Mason took Ford to the site, and Ford wrote about the discovery in the Journal of the Yorkshire Geological Society. The holotype (the original fossil used to describe the species) is now displayed in Leicester Museum & Art Gallery, along with a cast of a related fossil called Charniodiscus.

It was later found that Tina Negus, a 15-year-old student, had seen the same fossil a year earlier. However, her geography teacher did not believe it could be a Precambrian fossil. Mason and the museum’s display about Charnia note that Negus discovered the fossil first, "but no one took her seriously." She was honored during the 50th anniversary celebration of the official discovery.

Significance

Charnia is found in fossils as small as 1 cm (0.39 in) and as large as 66 cm (26 in) in length. It is an important fossil because it was the first ever described to come from rocks of the Precambrian time. Before 1958, scientists believed the Precambrian period had no fossils and possibly no large life forms. Similar fossils were discovered in the 1930s (in Namibia) and 1940s (in Australia), but these were thought to be from the Cambrian period and not considered unusual. At first, Charnia was thought to be an alga, but by 1966, it was reclassified as a sea pen, a group related to modern soft corals. Accepting Charnia as a Precambrian life form led to the discovery of other Precambrian animal groups. However, the sea pen idea has since been questioned, and scientists now admit they do not fully understand Charnia’s classification.

In the mid-1980s, Adolf Seilacher proposed that Charnia belonged to an extinct group that lived only during the Ediacaran Period. This theory suggests that many ancient fossils previously thought to be related to modern animals might instead be more closely connected to each other than to any living group. This group was named Vendobionta, a category with unclear ties to other groups, possibly sharing a unique structure made from a single type of cell.

The holotype of Charnia is displayed at the Leicester Museum & Art Gallery. A 2007 seminar honored Charnia as "Leicester's fossil celebrity." A 2021 study of Charnia’s shape and growth concluded that it and similar rangeomorphs were early eumetazoans, not closely related to any living animal group.

Ecology

Charnia's ecology is not well understood. It lived on the ocean floor and did not move. One widely accepted idea suggests it lived in deep water, below the reach of waves, where sunlight could not reach. Because Charnia lacks a mouth or digestive system, scientists do not know how it obtained food. Some researchers believe it may have filtered nutrients from water or absorbed them directly, and this remains an active area of study.

The growth patterns of the Ediacara biota are still being studied, which has led scientists to reject the sea pen hypothesis. Unlike sea pens, which grow by adding new parts at their base, Charnia grew by adding new parts at the top of its structure.