An early chordate, misunderstood for a century and lost for over half a billion years. Meet Pikaia Gracilens, the first true chordate (precursor to vertebrates) discovered from the Cambrian period.
Misunderstood by its discoverer, the famous Burgess Shale patron Charles Doolittle Walcott thought it was a worm and shelved the fossil in 1911.
Until it was re-examined in the 1970s and found to be a primitive chordate – the earliest of its kind known. And, overnight, Pikaia became an evolutionary giant.
But Pikaia is not the ancestor once claimed, there’s a much deeper story to this 505-million-year-old chordate.
Here’s what you need to know about Pikaia…
About Pikaia
It’s Scientific Classification
Domain: Eukaryota
Kingdom: Animalia (Metazoa)
Subkingdom: Eumetazoa
Infrakingdom: Bilateria
Superphylum: Deuterostomia
Phylum: Chordata
Family: Pikaiaidae
Genus: Pikaia
Species: Pikaia gracilens
Time Frame: When did Pikaia First Appear on Earth?
The first and only fossils we have of Pikaia are all from the same sedimentary layers of the Burgess Shale, meaning we only know it from one moment in time – 505 million years ago, in the Middle Cambrian.
Chordate Characteristics (Synapomorphies)
Pikaia displays quintessential chordate traits: a notochord, a dorsal nerve cord, and myomeres (muscle segments). These features are seminal to chordates, indicating its pivotal role in their early evolutionary history.
Before this creature was discovered, no one would have guessed chordates could have been around so early in Earth’s history.
Description: What was it Exactly?
We now know that Pikaia Garcilens was an early marine chordate, whose contemporaries would be among those lineages that would eventually lead to us vertebrates.
Now extinct, it’s not a direct vertebrate ancestor, though, just an extremely important fossil for our understanding of where we vertebrates – from T Rex to Smilodon and you and I – come from.
8 Incredible Facts about Pikaia Gracilens
1, When did Pikaia Go Extinct?
Pikaia gracilens, a hallmark of the Cambrian explosion, thrived, as far as we know, only in a specific slice of the middle Cambrian period, roughly 505 million years ago.
Its exact extinction timeline is unclear – we haven’t found any more fossils of it in rocks from different times. But it’s likely it went extinct at least by the end of the Cambrian time, approximately 488 million years ago.
Find out why in our look at: When did Pikaia go extinct?
2. What did it Eat?
Excellent question! If you look closely at the fossil, you’ll see it has these strange protruding structures below the head part – which some people proposed as appendages.
But if you look at its closest living (modern) relatives, the cephalochordates (lancelets), they have similar structures used as filters for water passing into the gills, which it uses to feed (not breathe, funnily enough).
And while we don’t have any direct fossil evidence of Pikaia’s diet, its body suggests it could have been a filter feeder or scavenger.
Find out more about: What did Pikaia eat?
3. What did Pikaia Evolve From?
It’s almost impossible to say since it’s a miracle we even have this early chordate preserved – its body is so soft and squishy.
We can deduce from its notochord and other chordate features that it must have evolved from earlier, more primitive deuterostome invertebrates.
Pikaia’s existence represents a significant point in the evolution of chordates, displaying key features that would lead to the development of more complex life forms – a pivotal evolutionary step towards all of us vertebrates.
Explore in-depth: What did Pikaia evolve from?
4. Size: How Big was It?
Now this we know with absolute certainty because we can just measure the fossil specimens. Pikaia gracilens was quite small, with most specimens measuring between 4 and 5 centimetres (approximately 2 inches) in length.
This modest size suggests it occupied a specific niche within the Cambrian ecosystems – probably lying low and hiding from predators.
Discover more insights on Pikaia’s size.
5. What is so Special about Pikaia?
It’s exceptionally special for its position as one of the earliest known chordates (the precursors to vertebrates), providing key insights into the early evolution of this group.
Its body plan includes primitive versions of features that are central to all chordates, such as a notochord and a dorsal nerve cord, marking it as a significant leap in the evolution of complex organisms from simpler ancestors.
Discover loads more amazing insights into what is so special about Pikaia.
6. Did Humans Evolve from Pikaia?
A notochord, dorsal nerve chord, post-anal tail and pharyngeal gill slits. The Cambrian fossil has all the features of a primitive chordate, which is the evolutionary precursor to all vertebrates.
And we humans are vertebrates, so you’d be forgiven for wondering if this ancient worm/eel-like creature is our ancestor.
But, in fact, it is not – it’s an offshoot from the main evolutionary line that leads to vertebrates and eventually to us humans.
Find out why with an in-depth look at: Did humans evolve from Pikaia?
7. Was it a Fish?
A notochord, streamlined body, gill slits and fin-like structures on the tail. When Charles Doolittle Walcott first discovered the fossils of the enigmatic metazoan in Canada’s Burgess Shale in 1911, he thought it was a worm.
But then we discovered in the 1970s that it’s actually a chordate – the precursor to vertebrates. This led some people to look at its body and habitat (the ocean) and ask, hey, is this a fish?
Sadly, the answer is no. Pikaia predates the evolution of true fish, lacking definitive fishy characteristics such as jaws, scales and fins, as we recognise them today.
But it lived with the creatures that would become true fish – find out more in: Is Pikaia a fish?
8. Did Pikaia have bones?
Gill openings, a nerve chord and a primitive backbone. Pikaia gracilens stands out among all Cambrian creatures as an early chordate, the ancient precursors to all of us vertebrates.
Funny enough, though, Pikaia did not have bones the way we know them – it was still technically an invertebrate.
But it was part of a major step toward creatures developing bones – learn more in our post on: Did Pikaia have bones?
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 vertebrates 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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