Editing Rangeomorph (section)

== 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>