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Giant Cambrian shrimp (520 mya) making waves, turns out to NOT be predator

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(So we cancelled the Fri Nite Frite. 😉 )

From Discovery News:

A top predator approximately 540 million years ago was an over two-foot-long shrimp relative that was the first known actively swimming filter feeder, according to the latest issue of Nature.

It was perhaps the most peaceful time on the planet, since the shrimp-like animal, Tamisiocaris borealis, had no predators and did not have to chase and attack prey.

“It is unlikely that there was anything that hunted Tamisiocaris,” lead author Jakob Vinther told Discovery News. “It was among the largest animals of its time. Therefore, it could calmly swim around and eat like a gentle giant without feeling the slightest hint of a threat, just like modern whale sharks (do today).”

Yes, that part sounds like a bit of a fairy tale to us too, but anyway, here’s Nature:

Such behaviour has evolved several times in Earth’s history, all during periods when marine food supplies were abundant, Vinther adds. But T. borealis is the earliest-known large, swimming filter-feeder.

Earlier fossil evidence has shown claws that are adapted for spearing or catching animals and makes a clear case for anomalocarids being predatory, says Robert Gaines, a geobiologist at Pomona College in Claremont, California. But the fine, feather-like spines of T. borealis are “a classical adaptation for filtering small plankton or zooplankton”, he says.

From letter to Nature: Large, actively swimming suspension feeders evolved several times in Earth’s history, arising independently from groups as diverse as sharks, rays and stem teleost fishes1, and in mysticete whales2. However, animals occupying this niche have not been identified from the early Palaeozoic era. Anomalocarids, a group of stem arthropods that were the largest nektonic animals of the Cambrian and Ordovician periods, are generally thought to have been apex predators3, 4, 5. Here we describe new material from Tamisiocaris borealis6, an anomalocarid from the Early Cambrian (Series 2) Sirius Passet Fauna of North Greenland, and propose that its frontal appendage is specialized for suspension feeding. The appendage bears long, slender and equally spaced ventral spines furnished with dense rows of long and fine auxiliary spines. This suggests that T. borealis was a microphagous suspension feeder, using its appendages for sweep-net capture of food items down to 0.5?mm, within the size range of mesozooplankton such as copepods. Our observations demonstrate that large, nektonic suspension feeders first evolved during the Cambrian explosion, as part of an adaptive radiation of anomalocarids. The presence of nektonic suspension feeders in the Early Cambrian, together with evidence for a diverse pelagic community containing phytoplankton7, 8 and mesozooplankton7, 9, 10, indicate the existence of a complex pelagic ecosystem11 supported by high primary productivity and nutrient flux12, 13. Cambrian pelagic ecosystems seem to have been more modern than previously believed. – Vinther, J., Stein, M., Longrich, N. R. & Harper, D. A. T. Nature 507, 496–499 (2014).

(Schmumble, file this one in the “More modern than previously believed” database.)

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Animation vid:

Hat tip: Daniel Quinones


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