Editing Rangeomorph

{{Use dmy dates|date=July 2022}}
{{Automatic taxobox
| fossil_range = {{fossilrange|635|505}} Possibly one of the last representatives of the Ediacaran biota.
| image = Charnia.png
| image_caption = ''[[Charnia]] masoni'', a rangeomorph
| taxon = Rangeomorpha
| authority = Hofmann ''et al.'', 2008
| subdivision_ranks = Subtaxa
| subdivision =

* †''[[Avalofractus]]''
* †''[[Broccoliforma]]''
* †''[[Fractofusus]]''
* †''[[Frondophyllas]]''
* †''[[Hapsidophyllas]]''
* †''[[Hylaecullulus]]''
* †''[[Khatyspytia]]''
* †''[[Pambikalbae]]''
* †''[[Pectinifrons]]''
* †''[[Plumeropriscum]]''
* †''[[Primocandelabrum]]''
* †''[[Trepassia]]''
* †''[[Vinlandia]]''
* †[[Rangeidae]]
** †''[[Rangea]]''
* †[[Charniidae]]
** †''[[Beothukis]]''
** †''[[Bomakellia]]''
** †''[[Bradgatia]]''
** †''[[Charnia]]''
** †''[[Paracharnia]]''
** †''[[Culmofrons]]''

| synonyms = *Charniomorpha
}}

The '''rangeomorphs''' are a group of [[Ediacaran]] [[Ediacaran biota|fossils]]. Ediacarans are the oldest large fossil organisms on earth, and many are not self-evidently related to anything else that has ever lived. However, some Ediacarans clearly resemble each other. Palentologists have not been able to agree on what else, if anything, is related to these organisms, so Ediacarans are usually classified into groups based on their appearance. These "[[Form taxon|form taxa]]" allow scientists to study and discuss Ediacarans when they cannot know what kind of living things they were, or how they were genetically related to each other. Rangeomorphs look roughly like fern fronds or feathers arranged around a central axis; the group is defined as Ediacarans with a similar appearance and structure to the genus ''[[Rangea]]''. Some researchers, such as Pflug and Narbonne, believe all rangeomorphs were more closely related to each other than to anything else. If true, this would make the group a natural [[taxon]] called '''Rangeomorpha''' (just as all insects are more closely related to each other than to any non-insects, and therefore are a natural taxon called [[Insect|Insecta]]). 

Rangeomorphs are a key part of the [[Ediacaran biota]], which survived about 30 million years, until the base of the [[Cambrian]], {{Ma|Cambrian}}. They were especially abundant in the cold, deep-ocean environments of the early Ediacaran, as shown in the [[Mistaken Point]] assemblage in [[Newfoundland (island)|Newfoundland]].<ref name=Narbonne2004/>

== Body plan ==

Rangeomorphs are [[fractal]] and [[Self-similarity|self-similar]] in form: they are made of branching sections, and each section repeats the same shape as the whole. The body "frond" is formed of branching "frond" elements, each a few centimetres long. Each of these is formed of many smaller "frondlets." Structurally, these are tubes held up by a semi-rigid organic skeleton. This body plan could have been formed using fairly simple developmental patterns.<ref name=Narbonne2004/>

== Ecology ==

Rangeomorphs dwelt in shallow to [[Abyssal zone|abyssal]] marine environments,<ref>{{cite journal | doi = 10.1073/pnas.1408542111 | volume=111 | issue=36 | title=Fractal branching organizations of Ediacaran rangeomorph fronds reveal a lost Proterozoic body plan | journal=Proceedings of the National Academy of Sciences | pages=13122–13126 | pmid=25114255 | pmc=4246981 | last1 = Hoyal Cuthill | first1 = JF | last2 = Conway Morris | first2 = S | author-link=Simon Conway Morris | year=2014 | bibcode=2014PNAS..11113122H | doi-access=free }}</ref> were unable to move, and had no apparent reproductive organs. They may have reproduced asexually by dropping fronds. Since many lived below the lowest level of the ocean where sunlight can penetrate, they could not have survived by [[photosynthesis]]. There is no evidence of a gut or mouth. One hypothesis is that nutrients from seawater were concentrated in their bodies by [[osmosis]]. Among living organisms, only osmotrophic bacteria live in this way, but the fractal branching tube structure of rangeomorphs gave them an unusual amount of surface area for every unit of body volume. This structure may have made it possible for osmotrophic organisms to grow to large sizes <ref name="Laflamme2009">{{Cite journal | last1 = Laflamme | first1 = M. | last2 = Xiao | first2 = S. | last3 = Kowalewski | first3 = M. | title = Osmotrophy in modular Ediacara organisms | journal = Proceedings of the National Academy of Sciences | volume = 106 | issue = 34 | pages = 14438–14443 | year = 2009 | doi = 10.1073/pnas.0904836106 | bibcode = 2009PNAS..10614438L | pmid=19706530 | pmc=2732876| doi-access = free }}</ref><ref>{{cite journal | doi = 10.1073/pnas.1403669112 | volume=112 | issue=16 | title=The advent of animals: The view from the Ediacaran | journal=Proceedings of the National Academy of Sciences | pages=4865–4870 | pmid=25901306 | pmc=4413262 | last1 = Droser | first1 = ML | last2 = Gehling | first2 = JG| year=2015 | bibcode=2015PNAS..112.4865D | doi-access=free }}</ref> However, other researchers argue this way of life is implausible, and suggest [[filter feeding]] or other mechanisms.<ref>{{cite journal | doi=10.1016/j.gr.2014.11.002 | volume=27 | issue=4 | title=Remarkable insights into the paleoecology of the Avalonian Ediacaran macrobiota | journal=Gondwana Research | pages=1355–1380| year=2015 | last1=Liu | first1=Alexander G | last2=Kenchington | first2=Charlotte G | last3=Mitchell | first3=Emily G | bibcode=2015GondR..27.1355L | doi-access=free | hdl=1983/ef181134-4023-4747-8137-ed9da7a97771 | hdl-access=free }}</ref> 

Most rangeomorphs were attached to the sea floor by a stalk ending in a circular [[holdfast (biology)|holdfast]]. Holdfasts were often torn from the frond by wave action or decay before fossilization, and are preserved as separate disc-shaped fossils that were given their own genus names (e.g. [[Aspidella]]).<ref name=jba>{{Cite journal |last=Antcliffe |first=Jonathan B. |last2=Brasier |first2=Martin D. |date=January 2008 |title=Charnia at 50: Developmental Models for Ediacaran Fronds |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2007.00738.x |journal=Palaeontology |language=en |volume=51 |issue=1 |pages=11–26 |doi=10.1111/j.1475-4983.2007.00738.x |issn=0031-0239}}</ref> Other rangeomorphs (such as the spindle-shaped ''[[Fractofusus]]'') lay flat on the sediment surface.<ref name="Xiao2009" />

Though we do not know what rangeomorphs were, aspects of their lives are revealed by the fossil record. In some areas, numbers of fronds of the same [[genus]] are found together. Analysis suggests that the genus ''[[Fractofusus]]'' could reproduce in two ways, first by setting a [[Propagule|particle]] of tissue loose in the ocean to land on the sea floor and develop into a new individual (a "grandparent"), and second, by "grandparents" spreading rapidly with [[Stolon|stolons]] to form surrounding groups of smaller "parent" and "child" fronds, just as modern plants such as [[Fragaria|strawberries]] spread by runners.<ref name="Mitchell Kenchington Liu Matthews 2015 pp. 343–346">{{cite journal |last1=Mitchell |first1=Emily G. |last2=Kenchington |first2=Charlotte G. |last3=Liu |first3=Alexander G. |last4=Matthews |first4=Jack J. |last5=Butterfield |first5=Nicholas J. |year=2015 |title=Reconstructing the reproductive mode of an Ediacaran macro-organism |url=http://eprints.esc.cam.ac.uk/3429/2/nature14646-s1.pdf |journal=Nature |volume=524 |issue=7565 |pages=343–346 |bibcode=2015Natur.524..343M |doi=10.1038/nature14646 |pmid=26237408 |s2cid=4471588 |hdl-access=free |hdl=1983/93446a6e-8c30-4927-992b-1f7fea755961}}</ref><ref name="University of Cambridge">{{cite web |last1=Collins |first1=Sarah |date=2015-08-03 |title=Earliest evidence of reproduction in a complex organism |url=https://www.cam.ac.uk/research/news/earliest-evidence-of-reproduction-in-a-complex-organism |access-date=3 August 2015 |publisher=University of Cambridge}}</ref> 

Fossil assemblages from Newfoundland and the UK reveal that rangeomorphs could live in large groups. At least seven genera are associated with filaments or stolons up to four meters long. These filaments ran across or through the bacterial mats on which Ediacarans lived, connected with the holdfasts (or the center of the body in genera without holdfasts), and at least in some cases, connected individuals together. This evidence suggests rangeomorphs may have fed by absorbing nutrients from the bacterial mats, and might even have been colonial organisms (such as corals are today) rather than groups of unrelated individuals.<ref>{{Cite journal |last=Liu |first=Alexander G. |last2=Dunn |first2=Frances S. |date=April 2020 |title=Filamentous Connections between Ediacaran Fronds |url=http://dx.doi.org/10.1016/j.cub.2020.01.052 |journal=Current Biology |volume=30 |issue=7 |pages=1322–1328.e3 |doi=10.1016/j.cub.2020.01.052 |issn=0960-9822}}</ref>

== 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. Early researchers thought they were [[Sea pen|sea pens]] ([[Cnidaria]]), but examination of well-preserved specimens of [[Charnia]] reveals that the branching fronds of rangeomorphs were fundamentally different from sea pens in both anatomy and growth pattern, and the modern consensus is that they are unrelated.<ref name=jba/> Rangeomorphs have at times been assigned to a range of modern animal and protist groups, but none of these classifications has withstood scrutiny;<ref name="Xiao2009">{{Cite journal| last1 = Xiao| last2= Laflamme | first1 = S.| first2 = M.| journal = [[Trends in Ecology and Evolution]]| volume = 24| title = On the eve of animal radiation: phylogeny, ecology and evolution of the Ediacara biota| issue = 1 | pages = 31–40 | date=January 2009 | pmid = 18952316 | doi = 10.1016/j.tree.2008.07.015}}</ref> they probably represent an extinct [[stem group]] to either the animals or fungi.<ref name=Narbonne2004>{{Cite journal| first1 = G. M. | title = Modular Construction of Early Ediacaran Complex Life Forms | journal = Science | volume = 305| issue = 5687| last1 = Narbonne | pages = 1141–1144 | date=August 2004 | issn = 0036-8075| pmid = 15256615 | doi = 10.1126/science.1099727|bibcode = 2004Sci...305.1141N | s2cid = 44647427 | doi-access = free }}</ref>  The fractal construction could be an adaptation to osmotic feeding that evolved independently in different groups, but most paleontologists now consider it to be a basic body characteristic inherited from a shared ancestor, which would mean the rangeomorphs are a natural [[taxon]] of organisms more closely related to each other than to anything else.<ref name=Xiao2009/> The quilted construction suggests a close affinity to the [[erniettomorph]]s, another form taxon of Ediacarans whose bodies were made from sheets of many small tubes.

== References ==
{{Reflist|30em}}

== External links ==

* Jeff Hecht: [https://www.newscientist.com/article/dn6162-fractal-patterns-of-early-life-revealed/ Fractal patterns of early life revealed]. On: New Scientist. 15 July 2004
* Tia Ghose: [http://www.livescience.com/47294-primitive-frondlike-fossils-reconstructed.html Gone! Why Ancient Fractal Creatures Vanished]. On: LiveScience. 11 August 2014 – Artist's reconstruction
* Brandon Specktor: [https://www.livescience.com/rangeomorph-fossils-social-network-filaments.html This 500 million-year-old 'social network' may have helped sea monsters clone themselves]. On: LiveScience. 5 March 2020
{{Petalonamae}}
{{Taxonbar|from=Q547464}}

[[Category:Rangeomorpha| ]]
[[Category:Petalonamae]]
[[Category:Ediacaran life]]

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