Small, worm/eel-like body and no apparent jaw. Pikaia Gracilens, a 505-508 million-year-old primitive chordate was not the biggest, scariest or most dominant creature in the ancient Cambrian seas.
It does give us some insight, though, into early chordate evolution. Specifically how creatures like Pikaia eventually gave rise to the vertebrates. A lineage that includes all the big predators, from Dunkleosteus to Dimetrodon to T Rex, Smilodon and all the way down to us humans.
But if Pikaia wasn’t at the top of the Cambrian food chain, what did it likely eat?
What Did Pikaia Eat?
Pikaia likely subsisted on tiny particles and microorganisms floating in the water or settled on the sea floor. Its body structure suggests a filter-feeding lifestyle, where it would have ingested nutrient-rich water and sifted out edible particles.
This method of feeding is common among some of the most ancient organisms, providing a base for the trophic web of the Cambrian seas.
In fact, if you consider Pikaia’s closest-living modern relatives are the cephalochordates (lancelets), small filter-feeding shallow marine creatures, you’ll see the family resemblance.
This points to a likely similar feeding habit in the 505/508 million-year-old chordate, Pikaia.
How Did Pikaia Likely Eat?
Given the apparent absence of a complex jaw or specialised feeding appendages, Pikaia probably relied on cilia, tiny hair-like structures, to create water currents directed towards its mouth.
This passive feeding mechanism likely allowed it to extract suspended organic material from the water, an efficient strategy in the nutrient-dense Cambrian oceans.
What Is So Special About Pikaia?
It is an example of one of the earliest known chordates, organisms that possess a notochord, a precursor to the vertebral column. This simple structure is a hallmark of the vast and diverse group of animals that includes everything from fish to humans.
Though it may be small, Pikaia‘s place in the fossil record provides critical clues about the origins and evolution of this fundamental characteristic – the backbone.
Explore in-depth: What is so special about Pikaia?
Did Pikaia Have Gills?
While Pikaia did not have gills in the way modern fish do, it likely possessed simple structures for gas exchange. As a deuterostome, it did have the ancestral pharyngeal gill slits.
We can see the evidence of this in Pikaia’s fossil evidence. In some early chordates, these gill slits seem to have served a dual function in both feeding and respiration, allowing water to pass over surface areas where oxygen could be absorbed.
So Was Pikaia a Fish, then?
No, Pikaia is not classified as a fish. It predates the emergence of true fish, lacking definitive fish features such as fins, scales, and a complex skeletal structure.
Pikaia represents a more primitive form of chordate, illustrating the early stages of evolution that would eventually lead to the diverse array of vertebrates seen today.
Discover more as we explore if Pikaia was a fish.
Did Pikaia Have Bones?
Pikaia did not have bones the way we know them. Instead, its internal structure was supported by a notochord, a flexible rod-like structure that ran along the length of its body.
At the time (over 500 million years ago) this notochord was a tremendous feat of evolution, providing skeletal support and allowing for limited movement. It’s a key feature distinguishing chordates from other animal groups.
Find out more about the search for whether Pikaia had bones.
Where Did the Pikaia Live?
Pikaia inhabited the ancient Cambrian seas, approximately 505 million years ago. Its fossils have been primarily found in the Burgess Shale of British Columbia, Canada. This is a deep-marine deposit, suggesting it lived in relatively deep marine environments.
There’s a good chance that Pikaia thrived in the low-light conditions of the sea floor or midwater. As far as we can tell, it lived at the base of a 1km marine shelf drop-off, along with some awesome Cambrian metazoan animals.
Discover: If Pikaia is a chordate, did humans evolve from Pikaia?
Fossil Locations: Where Are Cambrian Fossils Like Pikaia Found?
- Pikaia itself is only known from the Burgess Shale in British Columbia, Canada
- Yet other Cambrian sites include the Chengjiang fossil site in Yunnan Province, China
- The Wheeler Shale in the House Range of western Utah, USA
- The Sirius Passet site in North Greenland is another critical location for understanding Cambrian life.
Museum Fossils: Where can you Go to See Early Chordate and other Cambrian Fossils?
If you live nearby or can make the trip, there are a few great places to go and see some of the first animals and eumetazoans, including bilaterians, protostomes, deuterostomes and chordates, for yourself…
1. The Burgess Shale
Did you know you can actually go to the Burgess Shale fossil sites in the Canadian Rockies yourself? You can book a guided hike with The Burgess Shale Geoscience Foundation and visit the Walcott quarry, Mt. Stephen – the works.
Phone 1 (250) 343-6006, email info@burgess-shale.bc.ca or visit their website
2. Royal Ontario Museum
The Royal Ontario Museum in Toronto, Canada is famous for its connection to the world-famous Cambrian site, the Burgess Shale. They have both an amazing fossil collection if you visit in-person or even here online and a cool virtual sea odyssey you can experience online right now.
Phone: 416 586 8000 (Canada) | or visit their website
3. Smithsonian National Museum of Natural History
The Smithsonian has quite a large Cambrian fossil collection. And it’s completely free! So, if you’re ever in Washington DC, it’s one of the coolest places to go check out Cambrian fossils.
4. Chengjiang Fossil Site Natural History Museum
Being in China, it’s a bit hard to track down English info. But the Chinese government says there is a Chengjiang Fossil Site Natural History Museum. With over 60’000 fossil specimens at its location in Xincun Road, Chengjiang County, Yuxi City in Yunnan province.
5. The Natural History Museum, London, UK
With a rich collection of fossils and exhibitions that trace the history of life on Earth, the London Natural History Museum’s displays on Cambrian and Precambrian life provide context for the evolution of complex organisms.
Phone +44 (0)20 7942 5000 or visit their website.
6. Field Museum of Natural History, Chicago, USA
Boasting a broad collection of fossils and active in paleontological research, its Evolving Planet exhibition takes visitors through the history of life on Earth, including the Cambrian time.
Phone +1 312 922 9410 or visit their website.
Documentaries Featuring some of the First Chordates
They’re not always 100% accurate because we make new scientific discoveries all the time. But documentaries at least deliver the gist of the information in a fun and engaging way. Just click play, hit full screen and enjoy hours’ worth of awesome documentaries on first animals, right here…
1. Walking with Monsters
BBC, 2005
A bit older now and flashing past early animals a bit too quickly, this one in the “Walking With” series is still pretty cool for its Cambrian bits. It’s also available via Amazon.
2. Mankind Rising
2012
The 2012 TV movie production of Mankind Rising is a single animated journey from the earliest vertebrate ancestors right through to present-day humans. It’s pretty cool, maybe a bit dated, but still a lot of fun!
3. David Attenborough’s Rise of Animals: Triumph of the Vertebrates
BBC, 2013
Although more focused on the evolution of vertebrates, it’s still an awesome documentary to watch. It’s available to purchase from Amazon.
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