Rangea

{{Short description|Fossil taxon}} {{Use dmy dates|date=November 2025}} {{Automatic_taxobox | fossil_range =Ediacaran ~{{fossil range|558|549|ref=<ref name="Chen2014">{{cite journal | last1 = Chen | first1 = Zhe | last2 = Zhou | first2 = Chuanming | last3 = Xiao | first3 = Shuhai | last4 = Wang | first4 = Wei | last5 = Guan | first5 = Chengguo | last6 = Hua | first6 = Hong | last7 = Yuan | first7 = Xunlai | date = 2014 | title = New Ediacara fossils preserved in marine limestone and their ecological implications | journal = Scientific Reports | volume = 4 | article-number = 4180 | doi = 10.1038/srep04180 | pmid=24566959 | pmc=3933909| bibcode = 2014NatSR...4.4180C }}</ref>}} | image = Rangea scheiderhoehni 1.jpg | image_caption = ''Rangea scheiderhoehni'' from the Ediacaran Kliphoek Member of Dabis Formation on farm Aar, near Aus, Namibia. | taxon = Rangea | type_species = '''''Rangea schneiderhoehni''''' | type_species_authority = Gürich, 1929 }}

'''''Rangea''''' is a frond-like Ediacaran fossil with six-fold radial symmetry.<ref name="Vickers-Rich2013"/><ref name="Ivantsov_Leonov2009"/> 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- to decimetre-scale frond characterised by a repetitive pattern of self-similar branches and a sessile benthic lifestyle. Fossils are typically preserved as moulds and casts exposing only a leafy petalodium, and the rarity and incompleteness of specimens has made it difficult to reconstruct the three-dimensional (3D) morphology of the entire organism.<ref name="Sharp, Alana C. 2017">{{cite journal|last1=Sharp|first1=Alana C.|first2=Alistair R.|last2=Evans|first3=Siobhan A.|last3=Wilson|first4=Patricia|last4=Vickers-Rich|year=2017|title=First Non-destructive Internal Imaging of Rangea, an Icon of Complex Ediacaran Life|journal=Precambrian Research|volume=299|pages=303–308|doi=10.1016/j.precamres.2017.07.023 |bibcode=2017PreR..299..303S }}</ref>

Fossilized ''Rangea'' consists of several vanes. Each vane has a foliate shape with a series of recessed furrows that run outwards at varying angles from a prominent smooth median zone to define a series of chevron-like units called quilts. The quilts are arranged in two rows, that is, as long petaliform primary quilts and short lanceolate subsidiary quilts. The subsidiary quilts pinch out a short distance from the median zone as the primary quilts expand whereas the primary quilts extend to the edge of the frond where they taper bluntly. In no specimen can an exact total of primary quilts be counted, on account of either missing areas or incomplete preservation. The apices of the quilts are sharply delimited by wedge-shaped fields of either smooth or wrinkled relief that give this part of the body a scalloped appearance.<ref name="Grazhdankin, Dima 2005">{{cite journal|last1=Grazhdankin|first1=Dima|first2=Adolf|last2=Seilacher|year=2005|title=A Re-examination of the Nama-type Vendian Organism Rangea schneiderhoehni|journal=Geological Magazine|volume=142|issue=5|pages=571–582|doi=10.1017/S0016756805000920 |bibcode=2005GeoM..142..571G }}</ref>

thumb|''Rangea scheiderhoehni'' from the Ediacaran Kliphoek Member of Dabis Formation on farm Aar, near Aus, Namibia

A total of six species have been described, but only the type species ''Rangea schneiderhoehoni'' is considered valid: * ''R. brevior'' Gürich 1933 = ''R. schneiderhoehoni''. * ''R. arborea'' Glaessner, 1959 = ''Arborea arborea''. * ''R. grandis'' Glaessner et Wade, 1966 = ''Glassnerina grandis'' = ''Charnia massoni''. * ''R. longa'' Glaessner et Wade, 1966 = ''Akrophyllas longa''. * ''R. sibirica'' Sokolov, 1972 = ''Charnia sibirica'' = ''Charnia massoni''.

''Rangea schneiderhoehni'' fossils have been found in the Kanies and Kliphoek Members of the Dabis Formation and in the Niederhagen Member of the Nudaus Formation, Namibia. These deposits date from around 548 Mya. ''Rangea'' fossils have also been reported from the Ediacaran deposits of the Arkhangelsk region, Russia and in Australia. These fossils date from around 558-555 Mya.<ref name="Vickers-Rich2013"/><ref name="Ivantsov_Leonov2009">{{cite book |author1=Ivantsov, A. Yu. |author2=Leonov M. V. | title=The imprints of Vendian animals - unique paleontological objects of the Arkhangelsk region | year=2009 | location=Arkhangelsk | isbn=978-5-903625-04-8 | pages=91 | url=https://www.academia.edu/2355930 | language=ru}}</ref><ref name="Dzik2002">{{Cite journal | last1 = Dzik | first1 = J. | title = Possible ctenophoran affinities of the precambrian "sea-pen" Rangea | doi = 10.1002/jmor.1108 | journal = Journal of Morphology | volume = 252 | issue = 3 | pages = 315–334 | year = 2002 | pmid = 11948678| bibcode = 2002JMorp.252..315D | s2cid = 22844283 }}</ref> ''Rangea'' seems to have led a sessile existence.<ref name="Vickers-Rich2013">{{Cite journal | last1 = Vickers-Rich | first1 = P. | last2 = Ivantsov | first2 = A. Y. | last3 = Trusler | first3 = P. W. | last4 = Narbonne | first4 = G. M. | last5 = Hall | first5 = M. | last6 = Wilson | first6 = S. A. | last7 = Greentree | first7 = C. | last8 = Fedonkin | first8 = M. A. | last9 = Elliott | first9 = D. A. | last10 = Hoffmann | first10 = K. H. | last11 = Schneider | first11 = G. I. C. | title = Reconstructing Rangea: New Discoveries from the Ediacaran of Southern Namibia | doi = 10.1666/12-074R.1 | journal = Journal of Paleontology | volume = 87 | pages = 1–15 | year = 2013 | issue = 1 | bibcode = 2013JPal...87....1V | s2cid = 130820365 }}</ref>

New specimens provide evidence that ''Rangea'' was not a simple flexuous frond but a squat obconical fossil with radiating vanes which conjoin in a rather precise manner, so that the ridges corresponding to the axial traces on the branches on the reverse side of one frond exactly fit the depressions between the branches on the reverse side of the next, and the distal ends of the individual fronds meet virtually at a point. If the whole ''Rangea'' specimen is curved or deformed, then the same kind of curvature influences all its individual vanes. In one specimen, narrow wedges of sediment about 1–2 mm thick and some 5–6 mm deep penetrate the sutures between adjacent, conjoined fronds. This suggests that though it is usual for the lateral parts of the fronds to be tightly appressed and composite molded together, the individual fronds of the live organism were discrete structures, either largely or completely separate from those adjacent. The highly ordered, complex branching of the structural elements of the frond is a common characteristic and possibly reflects an unusual environmental parameter in early Ediacaran seas.<ref>{{cite journal|last=Jenkins|first=Richard J. F.|year=1985|title=The Enigmatic Ediacaran (late Precambrian) Genus Rangea and Related Forms|journal=Paleobiology|volume=11|issue=3|pages=336–355|doi=10.1017/S0094837300011635 |bibcode=1985Pbio...11..336J }}</ref>

thumb|''Rangea scheiderhoehni'' from the Ediacaran Kliphoek Member Dabis Formation on farm Aar, near Aus, Namibia

''Rangea'' likely had a rigid or semi-rigid skeleton-like structure that prevented buckling or compression and maintained integrity during life. Ediacaran-style preservation is thought to have been aided by microbial mats that covered the sea floor. The high abundance of quartz found within these specimens is consistent with infilling of the organism by detrital quartz and preservation in sandstone.<ref name="Sharp, Alana C. 2017"/>

Another peculiarity of ''Rangea'' is the clustering of several vanes into a closely packed compound structure. In each cluster all the constituent fronds demonstrate a similarity in quilt morphology and uniformity of quilt arrangement. Furthermore, these clusters maintain their integrity in winnowed specimens of Rangea. This implies certain stability and resistance of the cluster to mechanical stress. ''Rangea'' is reconstructed as an immobile benthic creature, whose body consisted of three closely packed trough-shaped fronds enveloped by a mucous sheath. Three-dimensional preservation and biostratinomy of the fossils suggest that in life ''Rangea'' was completely immersed into sand, and that the sand filled the cavities of the trough-shaped fronds. Living ''Rangea'' had a convex-down posture within the sediment, with the edges of all three vanes rising above sediment. Each frond consisted of two membranes, and the space between these membranes was inflated and fractally quilted. The quilts were probably hydrostatically supported. Composite moulding of the frond suggests that the quilt boundaries correspond to structures stiff enough to press through the integument.<ref name="Grazhdankin, Dima 2005"/>

Gregory Retallack considered that ''Rangea'' is not a benthic shallow marine fossil comparable with a sea pen but an alga or fungus from tidal flat or fluvial environments,<ref>{{Cite journal | last1 = Retallack | first1 = G.J. | title = Boron paleosalinity proxy for deeply buried Paleozoic and Ediacaran fossils | doi = 10.1016/j.palaeo.2019.109536 | journal = Palaeogeography, Palaeoclimatology, Palaeoecology | volume = 540 |year = 2020 | issue = 1 | pages = 279–284 | article-number = 109536 | bibcode = 2020PPP...54009536R | s2cid = 212771632 }}</ref><ref>{{Cite journal | last1 = Retallack | first1 = G.J. |title = Interflag sandstone laminae, a novel sedimentary structure, with implications for Ediacaran paleoenvironments | doi = 10.1016/j.sedgeo.2018.11.003 | journal = Sedimentary Geology | volume = 379 | year = 2019| pages = 60–76 | bibcode = 2019SedG..379...60R | s2cid = 135301261 }}</ref><ref>{{Cite journal | last1 = Retallack | first1 = G.J. | title = Were the Ediacaran fossils lichens? | doi = 10.1017/S0094837300012975 | journal = Paleobiology | volume = 20| issue = 4 | year = 1994| pages = 523–544 | bibcode = 1994Pbio...20..523R | s2cid = 129180481 }}</ref> however his theory about Ediacaran biota is controversial.<ref name="Waggoner1995">{{Cite journal |last=Waggoner |first=B. M. |year=1995 |title=Ediacaran Lichens: A Critique |journal=Paleobiology |volume=21 |issue=3 |pages=393–397 |doi=10.1017/S0094837300013373 |jstor=2401174 |bibcode=1995Pbio...21..393W |s2cid=82550765}}</ref><ref name="Waggoner2004">{{Cite journal |author=Waggoner, B. |author2=Collins, A. G. |year=2004 |title=''Reductio Ad Absurdum'': Testing The Evolutionary Relationships Of Ediacaran And Paleozoic Problematic Fossils Using Molecular Divergence Dates |url=https://repository.si.edu/bitstream/handle/10088/21610/iz_Waggoner_Collins_JP2004.pdf |journal=Journal of Paleontology |volume=78 |issue=1 |pages=51–61 |doi=10.1666/0022-3360(2004)078<0051:RAATTE>2.0.CO;2 |bibcode=2004JPal...78...51W |s2cid=8556856}}</ref><ref>{{Cite journal |author=Nelsen, M. |year=2019 |title=No support for the emergence of lichens prior to the evolution of vascular plants |journal=Geobiology |volume=18 |issue=1 |pages=3–13 |doi=10.1111/gbi.12369 |pmid=31729136 |doi-access=free}}</ref>

== See also == {{Portal|Paleontology}} * Rangeomorph * Ediacaran biota * List of Ediacaran genera

== References == {{Reflist}}

== Further reading == * {{cite journal|last1=Glaessner|first1=Martin F.|last2=Wade|first2=Mary|year=1966|title=The late Precambrian fossils from Ediacara, South Australia|journal=Palaeontology|volume=9|issue=4|pages=599–628}} * {{cite journal|last=Gürich|first=Georg|year=1930|title=Über den Kuibis-Quarzit in Südwestafrika|journal=Zeitschrift der Deutschen Geologischen Gesellschaft|volume=82|page=637|doi=10.1127/zdgg/82/637a|doi-access=free}}

Category:Ediacaran life Category:Rangeomorpha Category:Precambrian Africa Category:Fossils of Namibia Category:Fossil taxa described in 1929