The rangeomorphs are a

form taxon Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of sc ...

frondose Frondosity (from Latin ''frondōsus'' meaning 'leafy') is the property of an organism that normally flourishes with fronds or leaf-like structures. Many frondose organisms are thalloid and lack the organization of tissues into organs, with the ...

Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and th ...

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

that are united by a similarity to ''

Rangea ''Rangea'' is a frond-like Ediacaran fossil with six-fold radial symmetry. It is the type genus of the rangeomorphs. ''Rangea'' was the first complex Precambrian macrofossil named and described anywhere in the world. ''Rangea'' was a centimetre ...

''. Some researchers, such as Pflug and Narbonne, suggest that a natural

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

Rangeomorpha may include all similar-looking fossils. Rangeomorphs appear to have had an effective reproductive strategy, based on analysis of the distribution pattern of ''

Fractofusus misrai ''Fractofusus misrai'' is an Ediacaran fossil discovered in 1967 by S.B. Misra at Mistaken Point, Newfoundland and Labrador, Canada, which has since become the Mistaken Point Ecological Reserve. It was named after Professor Misra in 2007. It re ...

'', which consisted of sending out a waterborne asexual

propagule In biology, a propagule is any material that functions in propagating an organism to the next stage in its life cycle, such as by dispersal. The propagule is usually distinct in form from the parent organism. Propagules are produced by organisms ...

to a distant area, and then spreading rapidly from there, just as plants today spread by

stolon In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

s or runners. Rangeomorphs are a key part of the

Ediacaran biota The Ediacaran (; formerly Vendian) biota is a Taxonomy (biology), taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were composed of enigmatic tubular and frond-sh ...

, which survived about 30 million years, until the base of the

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

, which was . They were especially abundant in the early Ediacaran

Mistaken Point Mistaken Point Ecological Reserve is a wilderness area and a UNESCO World Heritage Site located at the southeastern tip of Newfoundland's Avalon Peninsula in the Canadian province of Newfoundland and Labrador. The reserve is home to the namesak ...

assemblage found in

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

Body plan

Rangeomorphs consist of branching "frond" elements, each a few centimetres long, each of which is composed of many smaller branching tubes held up by a semi-rigid organic skeleton. This self-similar structure proceeds over four levels of

fractal In mathematics, a fractal is a geometric shape containing detailed structure at arbitrarily small scales, usually having a fractal dimension strictly exceeding the topological dimension. Many fractals appear similar at various scales, as illu ...

ity, and could have been formed using fairly simple developmental patterns.

Ecology

Rangeomorphs dwelt in shallow to abyssal marine environments, were unable to move, and had no apparent reproductive organs. They possibly reproduced asexually by dropping off new fronds. There is little evidence of a gut or mouth, while the organisms have high surface area to volume ratios, which has led to the hypothesis that they gathered nutrients from seawater by

osmosis Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region of ...

. However, others argue this is implausible and suggest

filter feeding Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

or other mechanisms. Most were attached to the sea floor by a stalk or holdfast, although others (such as the spindle-shaped '' Fractofusus'') lay flat on the sediment surface.

Affinity

Rangeomorph communities are similar in structure to those of modern, suspension-feeding animals, but it is difficult to relate their morphology to any modern animals. They have at times been aligned to a range of modern animal and protist groups, but none of these classifications has withstood scrutiny; they probably represent an extinct

stem group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

to either the animals or fungi. Whilst the fractal construction may represent a convergent adaptation to osmotic feeding, most workers now consider it to be an

apomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

which establishes the rangeomorph clade as a valid taxonomic entity. The quilted construction suggests a close affinity to the

erniettomorph The Erniettomorphs are a form of Ediacaran fossil consisting of rows of airbed-like tubes arranged along a midline with a glide symmetry. Representative genera include '' Ernietta'', '' Phyllozoon'', ''Pteridinium'', ''Swartpuntia''. Undisputed ...

References

External links

* Jeff Hecht
Fractal patterns of early life revealed
On: New Scientist. 15 July 2004 * Tia Ghose

On: LiveScience. 11 August 2014 – Artist's reconstruction * Brandon Specktor

On: LiveScience. 5 March 2020 {{Taxonbar, from=Q547464 Ediacaran life Incertae sedis Petalonamae