Editing Cloudinidae (section)

==Ecology==
[[File:Cloudina NT.jpg|thumb| Restoration of ''Cloudina hartmannae'' with speculative mouth parts]]
''Cloudina'' is frequently found in association with [[stromatolites]], which are limited to shallow water; their [[isotope analysis|isotopic composition]]<ref>Ca/Mg ratios</ref> suggests that water temperatures were relatively cool. They have also been found in normal sea-floor sediments, suggesting that they were not only restricted to dwelling on microbial mounds.<ref name=domke2009>{{Walcott 2009|domke}}</ref> On the other hand, ''Cloudina'' has never been found in the same layers as the soft-bodied [[Ediacara biota]], but ''Cloudina'' and Ediacara biota have been found in alternating layers. This suggests that the two groups of organisms had different environmental preferences.<ref name="Miller" />

In many ''Cloudina'' specimens the ridges formed by the cones are of varying width, which suggests the organisms grew at a variable rate. [[Adolf Seilacher]] suggests that they adhered to [[microbial mat]]s, and that the growth phases represented the organism keeping pace with sedimentation—growing through new material deposited on it that would otherwise bury it. Kinks in the developing tube are easily explained by the mat falling slightly from the horizontal.<ref name=Seilacher1999>{{cite journal
 | author = Seilacher, A. | year = 1999 | title = Biomat-related lifestyles in the Precambrian
 | journal = PALAIOS | volume = 14 | issue = 1 | pages = 86–93
  | doi = 10.2307/3515363
 | jstor = 3515363
| bibcode = 1999Palai..14...86S }}</ref> Because of its small size, ''Cloudina'' would be expected to be found ''in situ'' in the microbial mat, especially if, as Seilacher suggests, sedimentation built up around it during its lifetime.  But all the many specimens discovered to date have only been found having been washed out of their places of growth. A further argument against Seilacher's hypothesis is that the predatory borings found in many specimens are not concentrated at what would be the top end, as one would expect if the animal was mainly buried. An alternative is that the organism dwelt on seaweeds,<ref name=Miller>{{Cite web
 | author = Miller, A.J.
 | year = 2004
 | title = A Revised Morphology of Cloudina with Ecological and Phylogenetic Implications
 | url = http://ajm.pioneeringprojects.org/files/CloudinaPaper_Final.pdf
 | access-date = 2007-04-24
 }}</ref> but until a specimen unquestionably ''in situ'' is discovered, its mode of life remains open to debate.

The tubes often appear to form colonies, although they are sometimes found in more isolated situations. The frequent appearance of large and sometimes single-species colonies has been attributed to the lack of significant predation.<ref name=Description /> On the other hand, in some locations up to 20% of ''Cloudina'' fossils contain [[predator]]y borings ranging from 15 to 400&nbsp;μm in diameter.<ref name="HUA2003">{{Cite journal|author=Hua, H.|author2=Pratt, B.R.|author3=Zhang, L.U.Y.I.|year=2003|title=Borings in Cloudina Shells: Complex Predator-Prey Dynamics in the Terminal Neoproterozoic|journal=PALAIOS|volume=18|issue=4–5|pages=454|bibcode=2003Palai..18..454H|doi=10.1669/0883-1351(2003)018<0454:BICSCP>2.0.CO;2|s2cid=131590949 |issn=0883-1351}}<!--| access-date = 2007-04-24--></ref><ref name=Bengtson1992 /> The boreholes are rather evenly distributed along the tube length, and some tubes had been bored multiple times—hence the organism could survive attacks, since predators do not attack empty shells. This may indicate that the animal could vary its position in the tube in response to predation, or that it occupied the full length—but not the full width—of the tube. The even distribution is perhaps difficult to reconcile with an [[infauna]]l lifestyle, mainly buried in a microbial mat, and adds weight to Miller's suggestion that the animal lived on seaweeds or in a reef environment. If modern-day molluscs are a suitable analogy, the size distribution of the borings suggests that the predator was similar in size to ''Cloudina''.<ref name="Brain2001">{{cite journal|author=Brain, CK|year=2001|title=Some observations on Cloudina, a terminal Proterozoic index fossil from Namibia|journal=Journal of African Earth Sciences|volume=33|issue=3|pages=475–480|bibcode=2001JAfES..33..475B|doi=10.1016/S0899-5362(01)00083-5}}<!--| access-date = 2007-04-24--></ref>

Fossil findings in the [[Nama Group]], [[Namibia]], suggest that ''Cloudina'' was one of the first reef-building animals,<ref name="natnews2014">{{Cite journal | doi = 10.1038/nature.2014.15470| title = Earliest skeletal animals were reef builders| journal = Nature| year = 2014| last1 = Morrison | first1 = J. | s2cid = 130499063}}</ref><ref name="penny2014">{{cite journal | doi = 10.1126/science.1253393 | pmid=24970084 | title=Ediacaran metazoan reefs from the Nama Group, Namibia | journal=Science | date=2014 | volume=344 | issue=6191 | pages=1504–1506 | first=A. M. | last=Penny|bibcode = 2014Sci...344.1504P | url=https://www.pure.ed.ac.uk/ws/files/16689099/Ediacaran_metazoan_reefs_Revised_1_.pdf |archive-url=https://ghostarchive.org/archive/20221010/https://www.pure.ed.ac.uk/ws/files/16689099/Ediacaran_metazoan_reefs_Revised_1_.pdf |archive-date=2022-10-10 |url-status=live | hdl=20.500.11820/44c8eba4-ec59-46d8-b868-b98c8ef1a113 | s2cid=206556938 | hdl-access=free }}</ref> but machine-learning facilitated 3D tomography indicates that the 'reef-forming' fossils are in fact simply aggregations of solitary individuals.<ref>{{Cite journal | title=Multiscale approach reveals that Cloudina aggregates are detritus and not in situ reef constructions| journal=Proceedings of the National Academy of Sciences| volume=115| issue=11| pages=E2519–E2527| date=2018-02-22| doi=10.1073/pnas.1719911115| pmid=29483244| pmc=5856547| last1=Mehra| first1=Akshay| last2=Maloof| first2=Adam| bibcode=2018PNAS..115E2519M| doi-access=free}}</ref>