An enigmatic, cup-shaped animal probably grew in groups to make feeding easier.
Ars Technica said:What drove the evolution of the earliest animal life? In modern animals, it's easy to infer a lot about an organism's lifestyle based on its anatomy. Even back in the Cambrian, with its large collection of bizarre looking creatures, these inferences are possible. Anomalocaris may have had a freakish, disk-shaped mouth, but it clearly was a mouth.
Go back to Earth's earliest animals in the Ediacaran, however, and things get much, much harder. There's only one species known so far that appears to have the right body plan to act as a predator of sorts. Beyond that, it's all a collection of soft-looking fronds and segments that are difficult to ascribe any obvious function to. Faced with a lot of questions without obvious answers, biologists turned to an unlikely source of help: physicists and engineers who understand fluid mechanics.
All of these creatures lived in an aquatic environment, so tracing how fluid flows across them can provide some hints as to how food might have arrived. Now, the same sort of research indicates that a strange cup-shaped species grew in communities because it improved the feeding of some of the community members.
Meet Ernietta
The Ediacaran period lasted almost a 100 million years, a period that included at least two snowball Earth periods. Despite the sometimes harsh conditions, it also contains the first indications of complex animal life, which appeared right after one of the global glaciations ended. Many of the creatures took forms that look almost plant-like; others are simple disks, sacs, or tubes. Few show any clear relationship to the animal life that appeared after it in the Cambrian, so figuring out their place on the tree of life has been a challenge.
Yet many of the fossil finds show clear evidence of entire ecosystems and indicate that different organisms flourished at different ocean depths.
Ernietta plateauensis, the species that's the subject of the new study, fits in well with its odd neighbors. The Wikipedia entry on the organism describes it as "bag-shaped," which is fairly accurate. Its body consists of a series of parallel tubes that form the wall of the bag. They're joined at a specialized structure at the bottom of the creature. Aside from an obvious inside and outside of the bag, there's not much in the way of an obvious internal structure.
One of the few things we can tell about Ernietta is that it was sedentary. Many of the fossils we've found of it contain multiple deposits of sediment layered on the bottom of the bag. This suggests it sat in the same place long enough to accumulate sediment from a number of separate events. The other thing we know is that they're gregarious, as large groups of them are found growing together.
Like many other Ediacaran organisms, there's no obvious mouth or anything apparent going on inside the organism that would indicate a mouth had somewhere to deliver food to. This raises an obvious question: how does it get enough food to survive?
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