The Long Arm of the Planktivore
by Brian Switek
The Cambrian oceans hosted a riot of evolutionary novelty. Over a seabead burrowed by penis worms and tread by living pincushions, multi-eyed invertebrates swung their schnozzles after prey and our closest, archaic relatives squirmed through the water.
Largest of all were the anomalocaridids – cousins of arthropods that flapped through the water on segmented wings and were equipped with a pair of “great appendages” hanging below a pineapple-ring mouth. Their size and flexible, spiky arms have made them dead ringers for apex predators in the eyes of paleontologists, but new research has cast at least one of these mind-bending invertebrates as a filter-feeder that was only a threat to plankton.
The pioneering planktivore was Tamisiocaris borealis, a relatively new addition to the anomalocaridid family tree named by paleontologists Allison Daley and John Peel in 2010. That description was based on a sole great appendage found in the 520 million year old rock of North Greenland’s Sirius Passet.
Against the slow grind of paleontology publication, however, discoveries in the field can quickly turn up additional parts of organisms that are already on their way to press. Expeditions in 2009 and again in 2011 uncovered additional appendages of Tamisiocaris in an even better state of preservation…
(read more: Laelaps blog - National Geo)
images: illustration by Rob Nicholls; Photo by Jakob Vinther/University of Bristol