Charnia – Ediacaran (579-555 Ma)I know what you’re thinking. One, this blog is supposed

Charnia – Ediacaran (579-555 Ma)I know what you’re thinking. One, this blog is supposed to be about animals, and two, the drawing today is really simple. To that I say 1) I’ll get to that in a minute, and 2) I have a big writeup today, because this is one of my favorite prehistoric creatures of all time, and I’m about to explain why.So, today we’re talking about an organism called Charnia. It’s old. Really really old. It lived during the Ediacaran period, over 550 million years ago. That’s before the Phanerozoic Eon even began. This is a Proterozoic organism, and boy howdy, is it weird.Charnia was a fern-like creature that attached itself to the seafloor. We aren’t really sure how it ate. It lived in deep waters, so it wasn’t photosynthesizing. It probably either filter fed or absorbed nutrients directly through the surface of its body. It’s been theorized to have an unusual and very simple method of growth. Its cells may have multiplied in a fractal pattern, giving it a super simple body plan with very few bells and whistles. It looked a lot like a sea pen. Except, it’s not even closely related to sea pens. In fact, it might not be closely related to anything at all.Charnia is a member of the loose collection of organisms called the Ediacaran biota. These were a bunch of simple aquatic organisms, who essentially came in two flavors: Fern and circle. And yet, they’re really, really important in understanding the evolutionary history of life on earth. So, for a long time, it was assumed that the Cambrian Explosion was when multicellular life got its start. It was where we found our oldest recognizable animals. Every modern phylum could be traced to the Cambrian, and there was nothing but microfossils in the rocks older than that. Surely everything was microscopic until it suddenly and rapidly became big. Charles Darwin admitted the Cambrian Explosion was a big issue with his theory, and like I said when I covered Opabinia, some people thought the CE was God’s moment of creation.But then knock knock, it’s Charnia, along with a bunch of other weird shit. Suddenly, we have multicellular life in the Precambrian, which was previously thought to be impossible. I’ve been avoiding the word “animal” because they’re… probably not animals? There’s a lot of mystery around the Ediacaran biota. Even though they’re typically really well-preserved, they’re so simple we can’t really infer anything about them beyond “They’re really old and they aren’t here anymore.” We have no idea what they could have eaten, if any of them were capable of powered movement, all that. They’re completely baffling to us because there’s nothing else like them, alive or dead. They may even represent a branch of the tree of life that isn’t around anymore. A completely separate experiment in multicellular life that never made it to this side of the Cambrian Explosion. Considering how utterly alien these things are, and considering they seem to have no descendants in the following periods, it’s entirely possible. It’s been suggested that, if fractal cell division was really how they grew, they were stuck with pretty simple body plans and were eventually out-competed as other organisms grew more complex.Multicellular animals in the Precambrian cause a bit of a problem. If all this weird shit lived before the Cambrian Explosion, did the CE even happen? Maybe there was no big radiation. Maybe all of these animals had already been evolving slowly during the Ediacaran, and we just don’t have the fossils.  Although, we don’t really have any evidence to support this idea, so take it with a grain of salt. So, that’s a basic rundown of what we know about the Ediacaran. Or, I guess, what we might know about the Ediacaran. The field is basically scientists looking at rocks with circles on them and going “uhhhhh.” I don’t blame them, though. It’s not the scientists’ fault these things are so weird. -- source link
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