Charnia
Encyclopedia
Charnia is the genus
name given to a frond
-like Ediacaran
lifeform with segmented ridges branching alternately to the right and left from a zig-zag medial suture. The genus Charnia was named after Charnwood Forest
in Leicestershire
, England
, where the first fossilised specimen was found.
Charnia masoni was brought to the attention of scientists by Roger Mason, a schoolboy who later became a professor of metamorphic petrology
, in 1957 in what is now a protected fossil site in Central England, and named by Trevor Ford a local geologist. Tina Negus, a 15 year old schoolgirl at the time, had seen this fossil a year previously but her geography schoolteacher flatly denied the possibility of Precambrian fossils. The holotype of this species now resides, along with its sister taxon Charniodiscus
, in New Walk Museum & Art Gallery, Leicester.
Charnia wardi, later discovered in 1978 in southeast Newfoundland, was first described in 2003. This is the longest known Ediacaran age fossil reaching in some instances over 2 m. The holotype is a fragmentary specimen with a C. masoni like structure. It was defined as a new species on the basis of long and narrow shape.
Charnia antecedens has more irregular and higher angles of branching than C. masoni.
A number of Ediacaran form taxa are thought to represent Charnia (or Charniodiscus) at varying levels of decay; these include the Ivesheadiomorphs
Ivesheadia, Blackbrookia, Pseudovendia and Shepshedia.
(Ford), it was spectacularly recast as a sea pen
(a sister group to the modern soft corals) from 1966 onwards (Glaessner). With this image of Precambrian sea pens in mind, the gates were open for the recognition of many other of the major animal groups in the Precambrian. However, this sea pen interpretation has recently been discredited,
and the current "state of the art" is something of a "statement of ignorance".
An increasingly popular theory has arisen since the mid 1980s, following the work of Prof Adolf Seilacher
who suggested that Charnia belongs to an extinct group of unknown grade that was confined to the Ediacaran Period. This theory suggests that almost all the forms that have been postulated to be members of many and various modern animal groups are actually more closely related to each other than anything else. This new group was termed the Vendobionta, a clade whose position in the tree of life is unclear, perhaps united by its construction via unipolar iterations of one cell family.
fossil. The greatest abundance of specimens, which are also the oldest reliably dated Ediacaran fossils, are found along the southeast coast of Newfoundland.
(perhaps a great deal below the wave base); this means it could not have photosynthesis
ed. Further it has no obvious feeding apparatus (mouth
, gut, etc) and so its ecology
remains somewhat of an enigma. Some have speculated that it survived either by filter feeding or directly absorbing nutrients and this is source of considerable and significant current research.
The growth and development of the Ediacara biota is also the source of continued research and it was this that was used to discredit the sea pen hypothesis. In contrast to the sea pens (that grow by basal insertion), Charnia grew by the apical insertion of new buds.
An article on the discovery of Charnia masoni:
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
name given to a frond
Frond
The term frond refers to a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group...
-like Ediacaran
Ediacaran
The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...
lifeform with segmented ridges branching alternately to the right and left from a zig-zag medial suture. The genus Charnia was named after Charnwood Forest
Charnwood Forest
Charnwood Forest is an upland tract in north-western Leicestershire, England, bounded by Leicester, Loughborough, and Coalville. The area is undulating, rocky and picturesque, with barren areas. It also has some extensive tracts of woodland; its elevation is generally 600 ft and upwards, the area...
in Leicestershire
Leicestershire
Leicestershire is a landlocked county in the English Midlands. It takes its name from the heavily populated City of Leicester, traditionally its administrative centre, although the City of Leicester unitary authority is today administered separately from the rest of Leicestershire...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, where the first fossilised specimen was found.
Diversity
Three species, C. masoni Ford 1958, C. wardi Narbonne & Gehling 2003, and C. antecedens Laflamme et al. 2007 can be distinguished on the basis of length/width ratios and the degree of attachment of adjacent branches.Charnia masoni was brought to the attention of scientists by Roger Mason, a schoolboy who later became a professor of metamorphic petrology
Petrology
Petrology is the branch of geology that studies rocks, and the conditions in which rocks form....
, in 1957 in what is now a protected fossil site in Central England, and named by Trevor Ford a local geologist. Tina Negus, a 15 year old schoolgirl at the time, had seen this fossil a year previously but her geography schoolteacher flatly denied the possibility of Precambrian fossils. The holotype of this species now resides, along with its sister taxon Charniodiscus
Charniodiscus
Charniodiscus is an Ediacaran fossil that was probably a stationary filter feeder that lived anchored to a sandy sea bed. The organism had a holdfast, stalk and frond. The holdfast was bulbous shaped, and the stalk was flexible. The frond was segmented and had a pointed tip...
, in New Walk Museum & Art Gallery, Leicester.
Charnia wardi, later discovered in 1978 in southeast Newfoundland, was first described in 2003. This is the longest known Ediacaran age fossil reaching in some instances over 2 m. The holotype is a fragmentary specimen with a C. masoni like structure. It was defined as a new species on the basis of long and narrow shape.
Charnia antecedens has more irregular and higher angles of branching than C. masoni.
A number of Ediacaran form taxa are thought to represent Charnia (or Charniodiscus) at varying levels of decay; these include the Ivesheadiomorphs
Ivesheadiomorphs
The Ivesheadiomorphs or pizza disks are a group of Ediacaran fossils that represent the remains of such taxa as Charnia and Charniodiscus, effaced by partial decay by micro-organisms....
Ivesheadia, Blackbrookia, Pseudovendia and Shepshedia.
Significance
Charnia is a highly significant fossil for several reasons. Firstly it is the first fossil that was ever described that came from undoubted Precambrian rocks. Until this point the Precambrian was thought to be completely devoid of fossils and consequently possibly of life. Despite similar fossils being unearthed in the 1930s (in Namibia) and the 1940s (in Australia) these forms were assumed to be of Cambrian age and so were considered unremarkable at the time. Secondly, Charnia has become an enduring image of Precambrian animals. Originally interpreted as an algaAlgae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
(Ford), it was spectacularly recast as a sea pen
Sea pen
Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 14 families within the order; they are thought to have a cosmopolitan distribution in tropical and temperate waters worldwide...
(a sister group to the modern soft corals) from 1966 onwards (Glaessner). With this image of Precambrian sea pens in mind, the gates were open for the recognition of many other of the major animal groups in the Precambrian. However, this sea pen interpretation has recently been discredited,
and the current "state of the art" is something of a "statement of ignorance".
An increasingly popular theory has arisen since the mid 1980s, following the work of Prof Adolf Seilacher
Adolf Seilacher
Adolf "Dolf" Seilacher is a German palaeontologist who has made major contributions to evolutionary and ecological palaeobiology in a career stretching over 60 years. He won the Crafoord Prize in 1992, the Paleontological Society Medal in 1994 and the Palaeontological Association's Lapworth Medal...
who suggested that Charnia belongs to an extinct group of unknown grade that was confined to the Ediacaran Period. This theory suggests that almost all the forms that have been postulated to be members of many and various modern animal groups are actually more closely related to each other than anything else. This new group was termed the Vendobionta, a clade whose position in the tree of life is unclear, perhaps united by its construction via unipolar iterations of one cell family.
Distribution
Charnia is both temporally and geographically the most widespread EdiacaranEdiacaran
The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...
fossil. The greatest abundance of specimens, which are also the oldest reliably dated Ediacaran fossils, are found along the southeast coast of Newfoundland.
Ecology
Little is known of the ecology of Charnia. It was benthic, anchored to the sea floor. According to one currently popular hypothesis, it probably lived in deep waters, below the wave baseWave base
The wave base is the maximum depth at which a water wave's passage causes significant water motion. For water depths larger than the wave base, bottom sediments are no longer stirred by the wave motion above....
(perhaps a great deal below the wave base); this means it could not have photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
ed. Further it has no obvious feeding apparatus (mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
, gut, etc) and so its ecology
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
remains somewhat of an enigma. Some have speculated that it survived either by filter feeding or directly absorbing nutrients and this is source of considerable and significant current research.
The growth and development of the Ediacara biota is also the source of continued research and it was this that was used to discredit the sea pen hypothesis. In contrast to the sea pens (that grow by basal insertion), Charnia grew by the apical insertion of new buds.
External links
For pictures of Charnia, see:- http://geol.queensu.ca/museum/index.php?option=com_content&view=article&id=55&Itemid=62
An article on the discovery of Charnia masoni:
- http://www.charnia.org.uk/newsletter/brit_assoc_2002.htm