Evolution: Apex predator became gentle giant

2014-11-17 13:49

(Shutterstock)

Multimedia   ·   User Galleries   ·   News in Pictures Send us your pictures  ·  Send us your stories

Washington - The so-called Cambrian Explosion, a critical juncture in the history of life on Earth when a dizzying array of animals first burst onto the scene half a billion years ago may have been even more explosive than previously known.

Scientists on Wednesday identified a weird sea creature dating from 520 million year ago that, like today's baleen whales and whale sharks, evolved from an apex predator to become a filter feeder, sifting the tiniest animals from the water.

The creature, called Tamisiocaris borealis, was a primitive relative of the arthropods, the group that includes crustaceans, insects and spiders. Nothing like it exists today.

Its fossilised remains were unearthed in 2009 at the northern-most tip of Greenland, the researchers said.

They recognised that it belonged to a group typified by the famous Cambrian Period creature Anomalocaris, known from a rich Canadian fossil site called the Burgess Shale, that were the first large predators ever to appear on Earth. They also were among the most bizarre-looking creatures on record.

While the size of Tamisiocaris - roughly 70cm long, may not sound impressive, it was among the biggest animals alive at the time, said paleontologist Jakob Vinther of the University of Bristol in Britain, who led the study.

"It was a gentle giant", said Vinther, whose findings were published in the journal Nature. "Even though this thing was not a whale or a whale shark, it evolved to become the equivalent."

Like its predatory cousin Anomalocaris, Tamisiocaris possessed a pair of spiny, grasping appendages up front to catch food, a pair of insect-like compound eyes on stalks and a circular mouth. Its body boasted a series of flaps down the sides that could be used for swimming, but it had no legs.

Spines on the grasping appendages of Anomalocaris were developed to spear or grab sizable prey. But in Tamisiocaris, these two appendages had a comb of long, slender, finely spaced spines that could be swept through the water to trap tiny creatures in the water like zooplankton, the researchers said.

"It would sweep its net-like appendages through the water, and then suck up whatever it caught", said University of Bath paleontologist Nicholas Longrich, another of the researchers.

It lived alongside primitive jawless fish that were the earliest vertebrates, horseshoe crab-like trilobites, primitive shellfish, relatives of starfish, jellyfish, sponges and others.

'New modes of life'

The Cambrian Period, from about 542 to 488 million years ago, was a pivotal point in the history of life when many major animal groups first appeared. The relatively short span of time in which this unfolded inspired the term Cambrian Explosion.

"It was a very active period of evolution. We were seeing the appearance of complex animals for the first time things with eyes, brains, jaws, legs and fins", Longrich said.

"Animals were trying out new modes of life burrowing, swimming and crawling. Previously, before the Cambrian Explosion, there were probably animals but they would have been minute, simple little worm-like things", Longrich added.

The presence of a large, free-swimming filter feeder like Tamisiocaris indicates the Cambrian oceans were rich with life and, in particular, loaded with plankton, the researchers said.

Several times in Earth's history, large marine predators have given up active predation - attacking sizable prey in favour of the more passive approach of filter feeding.

Baleen whales like today's enormous blue whale, which have plates of material called baleen on the upper jaw that act like a sieve to filter plankton, small fish and crustaceans evolved from toothed whales that were active predators. Filter-feeding sharks like today's whale shark, basking shark and megamouth shark arose from sharks that were fearsome hunters.

The newly identified creature's genus name, Tamisiocaris, means "sifter shrimp", and its species name, borealis, means "northern", for the northerly locale where it was found.

Join the conversation!

24.com encourages commentary submitted via MyNews24. Contributions of 200 words or more will be considered for publication.

We reserve editorial discretion to decide what will be published.
Read our comments policy for guidelines on contributions.
NEXT ON NEWS24X

24.com publishes all comments posted on articles provided that they adhere to our Comments Policy. Should you wish to report a comment for editorial review, please do so by clicking the 'Report Comment' button to the right of each comment.

Comment on this story
0 comments
Comments have been closed for this article.

Inside News24

 
/News

Book flights

Compare, Book, Fly

Traffic Alerts
There are new stories on the homepage. Click here to see them.
 
English
Afrikaans
isiZulu

Hello 

Create Profile

Creating your profile will enable you to submit photos and stories to get published on News24.


Please provide a username for your profile page:

This username must be unique, cannot be edited and will be used in the URL to your profile page across the entire 24.com network.

Settings

Location Settings

News24 allows you to edit the display of certain components based on a location. If you wish to personalise the page based on your preferences, please select a location for each component and click "Submit" in order for the changes to take affect.




Facebook Sign-In

Hi News addict,

Join the News24 Community to be involved in breaking the news.

Log in with Facebook to comment and personalise news, weather and listings.