8. Hallucigenia

Join palaeontologists Adele Pentland and Dr Martin Smith on a fossil fever dream through the Cambrian! This episode we discuss the spicy noodle Hallucigenia (an inch long worm with spikes, claws and Cthulhu tentacles), family ties to the velvet worms and frolic through the famous Burgess Shale in the Canadian Rockies.

Adele Pentland

8/23/202328 min read

Today's show is gonna be a real trip. We are talking about the Cambrian creature Hallucigenia.

This episode we talk about the legendary Burgess Shale, get down with worms and discuss the benefits of using a punk aesthetic for self defence.

Pals in Palaeo presents Hallucigenia

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This is Pals in Palaeo the show where we discuss the form, function and family groupings of extinct animals and other organisms. I'm your host, paleontologist, PhD candidate and fossil enthusiast Adele Pentland.

You can keep up to date with the show by following Pals in Palaeo on Instagram. Feel free to message me, especially if you have something nice to say but any constrictive criticism can be sent to our podcast producer and editor, @cesar_on_safari. Just kidding, but kind of not really. Please be nice to me, I'm doing my best and I'm only human.

Without further ado, let's get weird and talk about Hallucigenia!

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Pals in Palaeo acknowledges the Traditional Custodians of the land throughout Australia and their connections to land, sea and community. We pays our respects to the Elders past, present and emerging, and extend that respect to all Aboriginal and Torres Strait Islander peoples today.

This episode was recorded on Koa country, in Winton, central western Queensland, and fossils of Hallucigenia are known from sites across Canada and China.

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So I wanted to do some quick follow ups from our last episode which was on Arenaerpeton supinatus with special guest Lachlan Hart.

Ok first off the bat, let's talk about the plural for the word platypus. A platypus by the way is a monotreme which is an egg laying mammal we have here in Australia and as Lachlan mentioned, they swim around in the water but also spend time on the land. They're weird, but they're great. We love them here in Australia, and if I'm not mistaken there's even a platypus on the 20c coin.

Anyway, you might remember Lachlan wasn't sure what the plural of platypus was and I couldn't remember either.

This actually popped up the other day when I was listening to Just the Zoo of Us with Ellen and Christian Weatherford.

So, how plurals do is based on the language that word is based off of.
So in English, you add an s onto the end of a word to make it its plural form. It's actually the same with Portuguese which I'm currently learning, or trying to learn I should say, because I'm going on a little upcoming trip to Brazil. I don't think I've mentioned this on the podcast before, but yeah, I'll be going for a very short time with my supervisor Dr Steve Poropat as well as Professor Kliti Grice. So I did end up joining the Curtin lab, cannot remember if I mentioned that on a past episode, and we're all going to go over together and hopefully try and collect some fossils, all above board, have our paperwork like ticked and signed off and I'm so excited, it's going to be so much fun. There's obviously a lot of very cool pterosaur fossils I'm Brazil for me to look at as well as yeah, just a whole other country and can't wait.

But getting back to the platypus! So since platypus has Greek origins, the plural is platypuses or "platypodes". I personally prefer platypuses, but that's just me.

I also just want to acknowledge that when I said, "anything with a mouth can bite you" I was actually quoting Christian. Apparently when he was a kid, someone who worked at a pet store said that to him and it's like a core memory. But yeah, it comes up every now and then on Just the Zoo of Us and I wanted to cite the original source.

So not only did we talk about the plural of platypus, but Lachlan also mentioned Paracyclotosaurus, the Australian temnospondyl that got shipped off to the British Museum of Natural History.
So my supervisor for my PhD, Dr Steve Poropat who you'll hear from in an upcoming episode, he had a listen to the show and wanted to let me know about a new paper.
Different type of paper to what we normally talk about here on the show, that one was published by Alan Rix in The Royal Society of Queensland, and it's entitled
"The Dunstan Deals: How Some Geological Treasures Left Australia"

So Benjamin Dunstan was the Chief Government Geologist of Queensland from 1908 until 1931. And when he died, his personal collection of fossils and rocks, including somr meteorites was sold to the Natural History Museum in London.

Even though the Paracyclotosaurus holotype specimen was something Dunstan collected himself it's a bummer to think that he didn't donate it before he passed away. As for the meteorites though, that whole debacle definitely does not pass the pub test. He done wrong, he shouldn't have done that. Anyway, I could go on and on, if you're interested in reading more on that, the Dunstan Deals published by Alan Rix is available free in open access and I'll chuck a link to that paper in the show notes.

And the last follow up I had was on the cool palaeo art by friend of the show, designer cartoonist Zev Landes!

Zev is doing the art for the Bass Coast Dinosaur Trail down in Victoria and he's been cranking out some really fun fan art. So far he's drawn Cryolophosaurus from episode 5, Dunkleosteus which we talked about in number 6 and Arenaerpeton from our last episode!

Of all of the one's he's done so far Arenaerpeton's definitely my favourite. You can check out his stuff on Instagram @zevlandes, landes is spelt l-a-n-d-E-s but I also repost a lot of his stuff on the @palsinpalaeo Instagram, so you can find him that way.

By the way if you or someone you know uses Pals in Palaeo as like a creative prompt to create palaeo art based off our episodes, please tag me cos otherwise I might not see it! I'd love to see it, it makes me so happy to know that you're engaging with the show

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Today we're heading back to the no bone zone and talking about an invertebrate like no other.

Hallucigenia really does live up to its name: it looks more like something you'd stumble across in a fever dream, rather than a fossil found in the Canadian Rockies or the Cambrian of China.



We’ll get to it in a moment, but before we hear about Hallucigenia, I cannot wait to tell you about today's Random Fossil Fact. If this is your first time listening to Pals in Palaeo, we do things different ‘round here and instead of discussing and dissecting the news, you get to hear me bang on about weird and wonderful research on a host of different topics. Most of the time it's stuff I learned about years ago and have squirreled away in the back of my mind.

So it's not necessarily new research, but it is extraordinary, and still, super exciting!

Today's Random Fossil Fact is on de-extinction of a fossil plant.

If you're not familiar with the term de-extinction, it's essentially what the scientists in Jurassic Park were doing. Bringing a species back, after it's already gone extinct.

It's something that's coming up more and more these days, since teams of scientists around the world are working to resurrect things like the dodo a flightless bird, the thylacine (also known as the Tasmanian tiger which is a marsupial) and the woolly mammoth.

Of the 3 animal species I just mentioned, 2 of those were definitely hunted to extinction by us humans, so... attempting to bring them back feels like it's kind of motivated by guilt, and trying to right the wrongs of the past.

There's the argument that by reintroducing these animals into areas they once lived, order is being restored and their ecosystems will be back in balance. But of course, it's much more complicated than that and there's a lot to consider both ethically and ecologically.

I'm not going to get into the ethics of whether or not we should revive extinct species of animal, but if you're interested, Just the Zoo of Us another podcast hosted by the delightful Ellen and Christian Weatherford they talk about the pros and cons of de-extinction and more on the thylacine.

If you want to check that out, it's episode #185 and I'll put a link to that in the shownotes. They normally talk about extant species of animals on their show but they talked about the megalodon, the biggest species of shark to ever live and thylacine for that special episode.

Getting back to our Random Fossil Fact though, it's a lot easier to revive something that isn't that old. Kind of like, eating something after the best before date. You're better off eating something that's a couple days out of date, rather than months after it's expired or whatever. Theoretically, of course. I would never tell you you to eat food that's expired. This is just between me and you, smashed hat.

All this to say, the fresher the genetic material, the easier it is to work with. Because less of it has broken down, so there's more it to work with. And if it's been kept on ice for thousands of years, that's even better.

Like the de-extinction of the woolly mammoth, these specimens were collected from Siberian permafrost, which is honestly a bit of a goldmine when it comes to preserving genetic material in extinct organisms.

This paper was published by Svetlana Yashina and a team of Russian scientists in the Proceedings of the National Academy of Sciences (PNAS) in 2012. So in the ten plus years since these fossil plants were revived, we have not had a day of the triffids. Like, these plants did not then mutate and take over the world, which is good to know.

The paper by the way is titled "Regeneration of whole fertile plants from 30,000 year old fruit tissue buried in Siberian permafrost"

That paper is in open access so anyone can read it, and if you're interested, I'll put a link to that in the shownotes.

What I found interesting about these specimens, is that they weren't just in a random layer of sediment, they had actually been stashed in the burrows of fossil squirrels.

And as soon as I read that, all I could think about was Scrat from Ice Age, and I forgot to check but I'm fairly certain these weren't sabre-toothed squirrels. The burrows themselves were used for hibernation, and filled with hundreds of thousands of seed samples from a bunch of different plant species.

The squirrel burrows containing the special plant sample, were 38 metres which is, almost 125 feet, below ground and preserved in Late Pleistocene permafrost that had never been melted. Again, it's better to eat food that has been kept consistently cool, rather than reaching for something after you've just had a power outage for a couple days.

These fruits are 31, 800 years old, give or take 300 years. I know it's nice to have exact numbers but in the rare instances when you're actually able to work out the age of something using radioisotopes, there's always an error bar, which is why I said give or take 300 years. This is often written down as plus or minus however many years. This is also why some news articles discussing this paper said the fruit tissue was 32,000 years old.

All this to say, the plants they grew were a lot older than the previous record-holder. Before this, scientists had successfully grown date palms dating back to 2,000 years ago. I'll also put a link to that study in the shownotes but safe to say, the Siberian material has it beat, hands down.

For tens of thousands of years, the Siberian permafrost has kept this plant material at an average of -7°C (which is 19.4°F, so freezing cold).

The plants were grown from, "maternal, immature fruit tissue" from the Late Pleistocene and from that, they were able to grow the herbaceous plant, Silene stenophylla. Or that's what they thought they had at first, but more on that in a minute. This team of researchers actually first attempted to revive this plant using germinated fruits, but when that didn't work out, they were still able to get the results they wanted using immature fruit tissue.

Not only were they able to grow healthy plants, these flowered and set fruit, producing viable seeds. So again, this has broader implications for de-extinction proper and resurrecting breeding populations of an entire species, not just one individual.

By the way, if you want to see what this plant looks like, I'll also link to an ABC article summarising this research, but to paint you a word picture it's a very dainty plant, with white flowers with five petals. It actually reminds me a lot of the plant princess Zelda loves in Breath of the Wild, but from memory that had a bit of blue and the leaves are kind of different.

Now, since that original research article was published in 2012, there have been some follows up papers. These have all been focused on nailing down the taxonomy of this species of plant.

In 2012, the same year that first paper was published, a different team of researchers stated that the shape of the leaves and other features of the clones were most similar to Silene linnaeana. So, same genus, but different species.

Then shortly after that, the original team of researchers wrote a reply and acknowledged that whilst they had some good points, molecular data was needed to settle things, once and for all.

Then, for almost a decade, the identity of these plant clones was up in the air, until findings were published in 2022 by another team of Russian scientists, this time, led by Tatiana Kramina. Kramina and colleagues used molecular markers to determine that these were in fact, S. linnaeana. And if you want to read these papers, again, they'll all be in the shownotes and they're all in open access.

Since Silene linnaeana is still around today and grows in Siberia... I guess technically this doesn't count as de-extinction? Still, it's very cool and uses the same principles of de-extinction. Sorry if this counts as click bait but I was just desperate to talk about this amazing ancient plant and all the research that’s been done on it.

We've heard about cloning plants from the Late Pleistocene, which again was 32,000 years ago. Hold onto your butts, we’re about to go back in time and into the ocean, more than 500 million years ago and and deep dive into the delightfully weird Cambrian critter, Hallucigenia.

Before we talk about the Form, Function and Family Tree of Hallucigenia, let's set the scene so we can better understand this crazy looking creature.

Hallucigenia is from the middle Cambrian, so about 508 million years old, give or take a few million years.

As you might have guessed, the further back in time you go, the less recognisable things become. Kind of like, hopping in the car and things slowly changing and becoming less familiar. Well, unless you live in Europe or something like that, in which case things completely change if you head in the right direction but you get what I mean.

When scientists first stumbled across this little oddball, they couldn't work out which way was up, or how to tell the difference between the head and the butt end of the animal.

Well actually, that's not entirely true. But the first interpretation had this animal upside down and back to front, so...

And as it turns out, until about ten years ago now, they were actually missing the the head. Initially, scientists thought this little worm had a balloon shaped head, but on closer inspection, what they were looking at was fossil goo that had been squished out of the animal after it was buried and during the fossilisation process. In fact, the head was on the other end of the animal, and this interpretation has been bolstered by the identification of eyes and a mouth at this end, but more on that in a minute.

It just goes to show that one fossil can completely change our understanding of a species, or even an entire group of animals.

Now, as of this recording, there are three species, so Hallucigenia sparsa, Hallucigenia fortis and Hallucigenia hongmeia.

As I mentioned at the top of the episode, fossils of Hallucigenia have been found in the Canadian Rockies and in southern China. These two localities were close to each other in the Cambrian, which we talked a bit about in the Anomalocaris episode.

Even though there are 3 species of Hallucigenia, I'm gonna give you a general description of the animal, but, we'll be hearing from Dr Martin Smith a palaeontologist at the University of Durham and his research has largely focused on Hallucigenia sparsa from the Burgess Shale, so just keep that in mind.

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OK I've been hyping Hallucigenia up as being super strange, and honestly there is nothing that looks anything like it, alive today.

In terms of what Hallucigenia looks like... imagine a worm-like creature doing it's best impression of a singer from a punk rock band and you're halfway there.

Hallucigenia isn't a big animal, but they do range in size. The smallest are about half a centimetre to 5 and a half centimetres long, which for is equal to 1 fifth of an inch, to just over 2 inches. So little. If you travelled back in time to the Cambrian, you might accidentally squish one of these little critters and not even realise. Well, depending on whether you step on the spiky side or not. But more on that in a minute.

I couldn't find a weight estimate for Hallucigenia but we know about how big it is, and it's a thin, tube shaped animal with some other jazz going so it wouldn't have been super heavy.

I probably should have mentioned this earlier, but this worm-like animal also legs. As well as spines. The maximum number of legs is ten, so different to a centipede or millipede, which are types of myriapods which evolved a lot later in Earth history.

Most of the time, the legs on segmented animals are uniform. Like, you seen one, you seen 'em all. Unless they're right next to the face, in which case they might be a little shorter and more manoeuvrable, especially if that animal is a predator.

Hallucigenia, didn't get the memo. So starting at the front of the animal, the first 2 or 3 sets of legs near the head, are like thin spaghetti. And from what it looks like, they're very flexible. The remaining 7 or 8 pairs of legs, are a little thicker and end in either 1, or 2 claws on each foot (depending on the species).

As it turns out, the claws were one of several features that helped researchers, most notably, Dr Martin Smith work out how Hallucigenia fit into the animal kingdom.

Martin: So I’m Martin Smith, I’m a palaeontologist at the university of Durham in the UK.

Dr Smith is a top tier palaeontologist who has published his research on Hallucigenia in Nature and is the head of his own research lab at the University of Durham. He oversees work on ancient invertebrates, especially animals from the Cambrian. If you're interested in reading what else the Smith Lab works on, I'll put a link to their website in the shownotes.

Now, because Hallucigenia is so small, it takes a high powered microscope: a scanning electron microscope to really be able to see the finer features of this animal. Which is precisely what Dr Martin Smith, set out to do.

Martin: So when we took the Hallucigenia specimens over to the Electron Microscope, we weren’t really sure what we were going to find.

We’d already had some interesting observations of the spines along the back of the organisms that we’d wanted to follow up on, but we though “oh well, whilst we’re here, we really need to have a proper look all over”.

When we’d been looking previously at the claws, we’d been amazed at how much exquisite detail there was, that was actually preserved. And there’s a tone of specimens, there’s a few dozen.

And you hold them to the light and you just see something glinting and you think, “there’s something happening here”

So, we wanted to have a look at the eyes and to understand exactly how they were put together.

But it was amazing really, the first specimen that I put into the chamber, I closed the machine, I waited for it to rung up and… just sort of smiling back at me is this little face! These two little eyes and what looks like a big toothy grin. Well, it’s not quite a toothy grin.

That’s part of a ring of spines that would have surrounded its mouth. And then dot, dot, dot, dot, dot, all the way along its guts are these little black flecks that don’t really look like anything that we’ve seen before. And, they were, completely unexpected.

But once we saw them we though, “Ah! There’s a correlation to be made here.” There’s a connection to the throats and the mouths of other organisms within this group that contains the arthropods and the velvet worms.

And in fact, that allows us to draw some connections between Hallucigenia and this larger group that contains, all those living creatures.

I don't know what's more surprising: the fact that Hallucigenia had teeth or a pair of eyes. The teeth were also a bit of a surprise to the palaeontologists working on these fossils:

Martin: We hadn’t been expecting to find teeth at all in Hallucigenia. To some extent, that’s because nobody had suggested that any features like that were present in these lobopodians, which look like very simple organisms at first glance.

And secondly, it’s because there aren’t really similar features in the velvet worms, in their living descendants.

So what we’re looking at here is a vestige of the ancestral morphology, that is still preserved in Hallucigenia, but was lost later in the evolutionary trajectory.

And, whilst we were surprised at first, once we thought about this, we thought, actually yes, this does make a bit of sense.
It’s not as if, something wakes up one day and loses all of its evolutionary heritage and comes up with a completely new body plan.

And so, having these teeth here shows us that Hallucigenia is an intermediate: it’s got some of the old features, it’s got some of the new features, it’s somewhere in between and it’s showing us this gradual pathway from a spine-covered worm to something as derived and unusual as a modern velvet worm.

If you're not familiar with velvet worms, don't worry I'll talk more about them when we get to Hallucigenia's family grouping but for now, just picture a small worm living in the rainforest.

Like Martin mentioned before, even though at first glance Hallucigenia looked like it had a smiley face, it's teeth are actually arranged in a ring:

Martin: The dentition of Hallucigenia comprises a ring of spines that go around where the mouth was to put it simply. That would have probably been used to sort of suck food in. And then once the food gets into the mouth and into the throat it’s got these little needle-like spines along the top of the throat that presumably would have stopped food from coming back out again and directed it down into the back of the stomach and the digestive regions.

Some fossils from the Burgess Shale are so well preserved they can actually make out what the internal anatomy of this animal was like, and it looks like they have a simple gut. So nothing fancy but food goes in the mouth and exits out the other end. Which in my opinion is better than the alternative.

Aside from its mouth, the only other feature on Hallucigenia's head are a pair of simple eyes.

Simple eyes in invertebrates are sometimes called "eye spots" or ocelli, but they're all names for the same thing.

Ocelli, by the way, is spelt O-C-E-L-L-I (good Scrabble word) which are what jellyfish, sea stars, flatworms, snails, slugs and some arthropods use to see.

*gasp* wait, I just had a thought. You know how Ditto, the Pokémon Ditto that pink squishy blob always has dot eyes even when it transforms into other Pokémon? I reckon, Ditto has Ocelli. And that it can change other parts of its body, but it can't change its eyes. Probably not canon but it sounds good.

Anyway, the ocelli are better than nothing, but as Dr Martin Smith explains, these eye spots wouldn't have helped Hallucigenia see things in detail.

Martin: Yeah, Hallucigenia’s eyes were pit eyes, they were reasonably simple. Ocelli we call them. They were probably able to form a basic image, they were pretty large in comparison to the size of its head. But, it probably wasn’t going to benefit from an HD TV screen, you know, it’s vision would have been pretty blurry. But, certainly good enough to tell if a predator was coming.

Honestly, as long as it gives you a bit of an idea when a predator is around, then those eyes are doing their job.

And of course, the other thing you can do to protect yourself from predators is to shield yourself from their attack, or fight back. Hallucigenia has a series of spikes running along its back, which are quite long compared to the rest of the body and in the early days, these were mistakenly identified as Hallucigenia's legs.

And with that, let's talk about Function and spitball some ideas about what Hallucigenia was doing with its body.

The spikes along Hallucigenia's back were almost certainly used for self-defence.
Similarly, we see some caterpillars today adopting the same strategy, using spikes and other deterrents to ward off potential predators. This is particularly useful, if you have predators trying to swoop at you from above. Me personally, I hate picking prickles out of my socks and it's kind of the same principle with Hallucigenia, predators are less likely to want to eat something that will hurt them as they're grabbing it, especially if they don't have an easy way of avoiding or removing those spines.

I forgot to mention when I was describing the form of Hallucigenia, the spines aren't sticking straight up like a mohawk. Instead they occur in pairs along the back, and stick out at a bit of an angle. This makes a lot more sense than a single row of spines, since pairs of spikes that stick upwards and outwards will offer a bit more protection. The spines were quite stiff as well, so if something did try to grab them, it'll do some piercing damage. They're also very tall compared to the rest of the body. Its worth noting that lots of different animals have evolved spines and quills, and plants have also evolved spines and thorns. And of course, they can be made up of different things.

Since Hallucigenia has, for the most part, legs that end in claws, despite the fact that it's living in the ancient oceans of the Cambrian, it probably wasn't swimming around. Instead, those claws probably helped it get a grip as it walked along the ocean floor. The claws aren't super massive and even things like flies and other insects have legs that end in claws so again this was probably an evolutionary adaptation that helped Hallucigenia move around more than anything else.

I mentioned before when giving a general description of Hallucigenia that the first 2 or 3 pairs of appendages closest to the head are much thinner than the other legs, and they lack claws.

It's still a bit of a mystery as to what these were used for. During our conversation I had guessed that these helped Hallucigenia feed, like the raptorial appendages that the praying mantis has. If you look closely at a mantis, the legs closest to the mouth are different to the rest and used to hold and manipulate prey. But as Martin explains, this probably isn't the case for Hallucigenia, and the true purpose of these flexible tentacles is a bit unclear:

Martin: But, were those really thin tentacles really up to the task of moving food around? There’s a bit of a question mark as to what they were doing. Were they sensorial? It’s a bit hard to tell.

So maybe these tentacles helped Hallucigenia feel its way around? It seems we still have a lot to learn about this incredible creature, but one of the most recent revelations has been how Hallucigenia fits in the tree of life. We've heard about Form and Function, let's get into the family grouping of this spiky noodle.


Broadly speaking, Hallucigenia belongs to Panarthropoda, which is a big group that is mostly made up of arthropods, plus two other comparatively smaller clades.

The big one is Arthropods, which includes insects, arachnids, scorpions and ticks, as well as crustaceans. If something has an exoskeleton, i.e. a crunchy outer layer and needs to moult, chances are it's an arthropod. There are at least a million species of Arthropods on Earth today, so they're incredibly important in today's ecosystems.

But! Let's not forget there are two other clades included within Panarthropoda. This includes tardigrades, which are also known as water bears, and velvet worms.

Tardigrades are very small and range from half a millimetre to 1.2 mm. That's equivalent to, a fiftieth of an inch to a twenty-fifth of an inch. They're tiny! Tardigrades are able to enter a state of suspended animation, and have survived the vacuum of space. Mind you, they're not living their best life when they're out there but they can recover from it and continue living their lives.

The last members of the Panarthropoda are velvet worms, which as the name suggests are small, tube-shaped animals with antennae, stubby legs and covered in a fine fuzz.

Velvet worms are only found in damp places, including decaying logs and leaf litter. They look quite cute and harmless, but they actually hunt using slime and eat invertebrates.

If we zoom in, Hallucigenia is most closely related to modern velvet worms and fits within the phylum Onychophora. And, as we've touched on before, at first glance, Hallucigenia looks quite strange but there are hints of its heritage, hidden in plain sight.

Martin: Hallucigenia gotta score a 10 out of 10. It’s completely crazy. It looks, a little bit ridiculous, and that’s part of why I love it.

At the same time…

Once you start to realise what all these strange characteristics are, it does sort of make sense.

And it does fit into this pattern of diversity, that’s just been winnowed out by extinction.

And you know, who knows. If the Grim Reaper’s scythe had fallen on a slightly different set of organisms, maybe the rainforests today would be crawling with things that look like Hallucigenia, and, we’d be looking at things today that look like modern velvet worms and thinking, “Whoah! That’s a 10 out of 10 for weirdness”.

The other notes I have for the taxonomy of this animal is that Hallucigenia belongs to the Clade of 'Hallucishaniids' and the Order 'Hallucigeniidae'.

Honestly I thought it was impressive enough when an animal had a whole family named after it, but this is next level. I mean, a Clade with your name in it is had the same energy as women known by their first name: like Beyonce, Cher and Oprah. Hallucigenia might not be a household name but it's still iconic.

Part of the reason why Hallucigenia is notable is because we have multiple fossils of this creature, it's known from a few different sites across the globe, including the famous Burgess Shale.


Western scientists first became familiar with the fossils from the Burgess Shale in 1909 when Charles Walcott came across the site. As far as fossil localities goes, it was basically like winning the lottery. Not only are the fossils preserved in fine-grained sediment which helps capture a lot of detail, it was full of incredible animals.

Martin: It lives at a very interesting time, in life history. If we go back another 50 million years, then, there’s really not much living in the oceans that’s more complicated than a seaweed. There’s a few little wormy things, maybe.

But you fast forward 10-15 million years, and, almost all of the modern body plans, the sort of, ways of building an organism have, appeared in the fossil record.

So, Hallucigenia’s living at this time where evolution is really… it’s having a sort of creative master stroke, if you like. Lots of innovation is happening.

And so we’re seeing this combination in fossil deposits like the Burgess Shale, where Hallucigenia is preserved, of, organisms that are starting to look quite similar to modern groups.

But also some of those more ancestral morphologies, you know, the dead ends, the side alleys that didn’t make it through subsequent extinctions and so they look quite strange to modern eyes.

Over the course of 14 years, Walcott with his family in tow would collect hundreds of fossils from Burgess Shale. By the end of this saga in 1924, when Walcott was 74 he had collected 65,000 specimens.

I'm struggling to deal with how big that number is because honestly that'd have to be up there with the number of fossils in some museums. I can kind of understand why he did it though, because the Burgess Shale is famous for the high quality of its fossils.

By the way it's not like Walcott single-handedly pilfered every single fossil from this site, more fossils have been found since then.

Still, it's safe that Walcott bit off a little more than he could chew, still, he tried to get through and describe as many fossils as he could, something he pursued up until he died in 1927.

Walcott laid the foundation work for future palaeontologists, but he actually severely underestimated the diversity of the Burgess Shale fossil record. Part of that, is because as he was describing these specimens, as if they had died only a couple years ago. He was trying to fit these square pegs within the round holes of modern taxonomy.

What it boils down to is that some extinct groups are so far removed from everything we have around us today, that they need their own special categories.

It wasn't until the mid 1960s when other researchers started going through Walcott's work did they realise just how many different species they were dealing with.

What's special about the Burgess Shale as a fossil locality is that it preserves soft bodied organisms, as well as the hard parts of the body. Most fossil localities just preserve the hard parts, and fossils of soft tissue structures are very rare.

In fact, the exceptional quality of the fossils is the main reason why the Burgess Shale was designated a World Heritage Site in 1980. Then, four years later, it fell under the protection of the Canadian Rockies World Heritage Status. Which means, you can't just walk in there and collect fossils. Anyone who does, has gone through the proper checks and balances and obtained the right permits.

Getting back to nitty gritty details of the Burgess Shale, a shale is a very fine-grained sedimentary layer, and indicates a low energy depositional environment.

Shales are essentially the bottom of the ocean, so even though the Burgess Shale is currently situated on top of a mountain, and part of the Rockies in Canada, millions of years of geologic processes have shifted the position of this rock and through orogenesis, which is the scientific name for mountain building, things have been turned upside down. Or rather, two things have been pushed together and as they've slammed into each other, these ancient sea sediments have been stacked on top of other layers of sedimentary rock. It's these same natural forces that produced the Himalayas.

The Burgess Shale is also famous for other fossil invertebrates, including Anomalocaris and trilobites, and other lovable weirdos including Opabinia an animal with 5 eyes, a segmented body not too unlike a trilobite and a trunk like appendage at the front of its face.

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Before we wrap up, let's quickly talk about where you can learn more about Hallucigenia and how it has influenced pop culture. Unfortunately, there's not a lot to talk about with this creature. It seems no one wants to cuddle up next to a Hallucigenia plushie, but it does come up on occasion when the Burgess Shale is mentioned.

One of the earliest books written on the Burgess Shale was by Stephen Gould, titled 'Wonderful Life' published in 1989. Keep in mind, we've learned a lot about fossils from the Burgess Shale since it was published, and a lot of that wonderful research has been fueled by advancements in technology.

Getting back to that book through, I just had a quick look online and while there's some disagreement about the conclusions the book comes to it but having said that, I just want to put it out there that I haven't read this one. I'll be honest, I'm not a big reader of books since I've been at uni, but if you have read it, let me know what you thought of it. You can always DM me @palsinpalaeo on Instagram.

If you're like me and not much of a reader but happy to watch a documentary, our good friend David Attenborough has you covered. Hallucigenia features in David Attenborough's 'First Life' which is a 2 hour exploration of Earth's first multicellular animals. Normally I'm more than happy to recommend Attenborough to anyone but bear in mind this series came out in 2010, so 5 years before scientists had discovered Hallucigenia's missing head. So yeah. Sadly you can't believe everything you see on TV, but until David Attenborough revisits this time period, it'll have to do.

Other than that, I found the Nature video with Dr Martin Smith who we heard from on today's episode really informative. It's on YouTube, and if you want to check it out I'll link it up in the shownotes. It shows replicas of some of the Burgess Shale fossils, a close up of the eyes and mouth of Hallucigenia, and, a reconstruction of what Hallucigenia looked like when it was alive. That 3 minute video alone sums up just about everything we covered in this episode. Still, I hope you enjoyed hearing me talk about Hallucigenia.

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Thanks so much for listening and a big Pals in Palaeo thank you to Dr Martin Smith who responded to my very dorky email and was incredibly generous with his time.

This episode wouldn't be nearly half as good without his input, and even though I was initially hesitant to have guests on for just about every episode, it's been wonderful hearing about research that's wildly different from what I'm working on and dive into different topics with the help of true experts in the field.

As always, thank you so much for hanging out with me today, and, if you've gone to the effort of listening to every single episode so far, from very bottom of my heart thank you.

I'm having a lot of fun putting these together and working with my good mate César on these so, if you're still enjoying them, and we're willing and able, we'll keep making the show in some shape or form.

Might need to take a break in between seasons, but we'll find a way to make it work I promise. To keep up to date with the show and find out when the next episode drops, you can follow us on Instagram @PalsinPalaeo.

Speaking of César, the show literally wouldn't be what it is without his help he does editing and produces the podcast. He along with my mate Grace were the two people who really pepped me up to do the podcast.

Big thank you to Hello Kelly for our amazing theme music and the other tunes on the podcast. If you want to hear more Hello Kelly songs filled with synths and guitar riffs, definitely check out their latest album Sweet Nostalgia on Spotify, Band Camp and everywhere else you get music. Special thanks for Francy for workshopping the theme song with me, I had a rough idea but he just took it to the next level and it sounds so freaking good.

Final thank you goes out to Crumpet Club House, especially Jenny Zhao and Amy Franks for our podcast cover art. Don't forget you can get vinyl stickers with the podcast cover art and sticker sheets of the fossils from it to. It's a great way to support the show, spread the word and treat yourself so if you're interested in grabbing some of those, there'll be a link in the shownotes.

The next episode, is the final show for season 1 but don't worry, it's gonna be an absolute cracker. I've spent ages working on it and if it's not any good, at the very least it's gonna be a solid hour of content. If you liked today's show and you want to give back, please take a second to rate and review the show. Yes it makes me smile, but more importantly it also helps us grow and connect with more people who wanna learn about palaeontology.

Pals in Palaeo will be back in 2 weeks time with one last episode for season 1, but until then, take it easy and I'll talk to you soon.


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