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October 4, 2011
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Cambrian Microbial Mat by NocturnalSea Cambrian Microbial Mat by NocturnalSea
For the vast majority of Earthís history, most of the ocean floor was covered by tough microbial mats. It was only in the Cambrian period that these mats were finally broken up by burrowing animals, creating the relatively soft, sediment-based ocean bottoms we know today. During the Cambrian many animals evolved to feed upon these microbial mats using rasping, radula-like organs. Here Iíve illustrated a small assortment of them:
The red, scaled creatures with the blue dorsal spines are Wiwaxia.
The green, yellow-spined critters are Orthrozanclus.
The brown, sausage-shaped things with the shell at either end are Halkieria.
The blue and yellow flatworm-like creatures are Odontogriphus.

Note that most of these creatures have armored scales and/or sharp spines as defenses against the many large Cambrian predators such as Sanctacaris in the upper left. While Odontogriphus was unarmored, Iíve imagined it here as a toxic animal like a seaslug. Its bright coloring advertises its unappetizing nature.

Well-developed microbial mats are stratified into several layers of microorganisms, usually with photosynthesizing cyanobacteria at the top. Here the mat-grazers have chewed away parts of this green cyanobacterial layer, revealing the purple-pink sulfur-utilizing bacterial layer below. The strings of white dots are bubbles of oxygen escaping from the edges of the cyanobacteria.

On the edge of this microbial mat is a forest of sponges, specifically: Crumillospongia, Halichondrites, Takakkawia, Pirania (with tiny Nisusia brachiopods attached to its spines) and Vauxia. Also growing among the sponges are the odd Chancelloria (the spiked, pink-purple sponge-like organisms). While they superficially resemble sponges, several anatomical features of the chancellorids indicate that they are unrelated to Porifera. They may, in fact, be highly modified relatives of Wiwaxia, Halkerieria and Orthrozanclus (although that view is still fairly controversial). Like the mat-grazers, many of these sponges have large spines, presumably to dissuade predators such as the blue lobopods feeding among them.

Note the strings of hydroid-like organisms spreading out of the sponge forest. These are actually the red algaeWaputikia.

Note also the tan, hydroid-like critters tucked among the sponges. These are Dinomischus. Like many Cambrian animals, their exact affinity is uncertain, but their closest living relatives are believed to be tiny, bryozoans-like animals called entoprocts.
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:iconrayney:
Rayney Featured By Owner Feb 7, 2014
Oh . . . I don't have words.
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:iconnocturnalsea:
NocturnalSea Featured By Owner Feb 22, 2014  Professional Traditional Artist
thanks :)

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:iconherofan135:
herofan135 Featured By Owner May 21, 2012  Hobbyist Traditional Artist
So amazing! The use of colour is great! You did an excellent job on this!
Weird to think that those animals that depended on the bacterial mats for their food, made them disappear, thus making themselves extinct. :P
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:iconnocturnalsea:
NocturnalSea Featured By Owner May 24, 2012  Professional Traditional Artist
Thanks. This one's a personal favorite of mine.
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:iconmeganbednarz:
meganbednarz Featured By Owner Oct 9, 2011   General Artist
Wow, really neat! Informative and beautiful at the same time :D
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:iconbabbletrish:
babbletrish Featured By Owner Oct 5, 2011  Professional Traditional Artist
Beautiful!
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:iconnocturnalsea:
NocturnalSea Featured By Owner Oct 5, 2011  Professional Traditional Artist
thanks!
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:iconavancna:
avancna Featured By Owner Oct 4, 2011  Hobbyist Traditional Artist
Obviously, you've heard of the bryozoan Archimedes, right?
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:iconnocturnalsea:
NocturnalSea Featured By Owner Oct 4, 2011  Professional Traditional Artist
Oh, so that's what that's called. I'd seen that fossil a couple times, but could never remember the name.
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:iconavancna:
avancna Featured By Owner Oct 4, 2011  Hobbyist Traditional Artist
Apparently, some researchers suggest that the frills were formed by a symbiotic red algae.
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:iconnocturnalsea:
NocturnalSea Featured By Owner Oct 4, 2011  Professional Traditional Artist
neato beanito
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:iconavancna:
avancna Featured By Owner Oct 4, 2011  Hobbyist Traditional Artist
Of course, that explanation doesn't explain why there are no zoonids on the coil/axis, or that the frill resembles your stereotypical bryozoan frill.
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:iconamnioticoef:
AmnioticOef Featured By Owner Oct 4, 2011
As always, your use of color is exquisite; I especially like the pattern on Sanctacaris.

How weird that the seafloor used to be covered in microbial mats. You know, it's been asked before, but I've never found a good answer; why haven't the plants on land been grazed into oblivion like the old mats? Why do we have dense aggregations of plants rather than bare dirt? Something to ponder.
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:iconnocturnalsea:
NocturnalSea Featured By Owner Oct 4, 2011  Professional Traditional Artist
Hmmm, interesting question.
Personally, I'd imagine it's due to the morphological diversity of plants. Being multicellular, plants can develop all sorts of defenses to fend off herbivores, such as toxins, spines, indigestible bark, rhizomes, tall trunks (which would put the leaves out of reach of all but the most specialized herbivores), etc. A bacterial mat, on the other hand, doesn't have a whole lot of morphological diversity; its ability to resist herbivores relies mainly on the sheer number of cells within it, and the speed with which those cells can reproduce to replace members lost to grazing.
On top of herbivores, a mat also has to contend with all the bioturbators breaking it up. Plants have lots of defenses to prevent other organisms from breaking them apart, such as tough wood, chemical defenses and symbiotic partners. Again, all bacterial mats have are sheer numbers and quick reproduction-- which usually isn't fast enough to compensate for the destruction caused by diggers.
And, don't forget, there are still a lot of microbrial mats on Earth, they're just located in places that are extreme (hydrothermal pools, salt lakes, acid lakes) or protected (mangrove forests, Shark Bay in Australia).
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:iconamnioticoef:
AmnioticOef Featured By Owner Oct 4, 2011
Yeah, that's kind of what I figured. Still, you might expect bacteria to evolve all kinds of crazy chemical defenses.
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:iconnocturnalsea:
NocturnalSea Featured By Owner Oct 4, 2011  Professional Traditional Artist
Actually, now that I think about it, there are STILL bacterial mats covering most of the earth-- they just tend to be less obvious against the backdrop of larger, more impressive organisms like trees. Most soils, for example, are held together by thick strands of bacterial glue, as are older sand dunes. And protected areas of the American deserts are almost completely covered by a crust of microorganisms. Check it out: [link]
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