If my intent is to convince people sharks are cute I’m definitely going about it the wrong way by including this one but I absolutely have to. The frilled shark is possibly one of the weirdest, most awesome sharks out there. It looks less like a shark and more like an eel, it has six pairs of gill slits, that project out slightly giving it the ‘frills’ after which it is named, and it is considered a ‘living fossil’ – basically a species that exhibits a primitive form compared to what we expect.
Until C. africana was described in 2009, C. anguineus was believed to be the only extant member of the genus Chlamydoselachus (I wish they would cut these silly names – sounds like a sexually transmitted disease).
C. africana was first suspected after a strange specimen of a frilled shark was caught off Namibia in 1988, obviously the fact that it wasn’t described until 2009 means there’s not an awful lot we can say about C. africana. Its distribution, unlike C. anguineus which is quite far ranging, seems to only be off the southern coast of Africa. It looks similar to C. anguineus, but with several notable differences in proportions (e.g. longer head, wider spaced eyes, wider mouth) and they seem to eat other, smaller, sharks.
So we’re mainly going to be talking about C. anguineus today and from now on I shall just call it the frilled shark, but not until I’ve explained the name. Chlamy- from the Greek for frill, selachus from the Greek for Shark, anguineus from the Latin for eel-like. Eel-like frilly shark – do-doo do-do doo-doo…STOP IT, damn song.
So they’re eel like, that’s for sure. Looking at a filled shark you wouldn’t think it was a shark at all, unless you knew a little summin-summin about prehistoric sharks. Then you’d look at it and think “You know that looks a lot like a lot of extinct sharks from the Carboniferous (around 360-300 million years ago!)”, at which point you’d suspect it might be a living relative of one of those families. After all it has the trademark tri-pointed teeth, a jaw attached to the cranium…
…Yeah, we haven’t discussed that yet, have we? Okay, well I’ll spoil something from the rest of this list. The Goblin Shark doesn’t make it, so let’s use that as our example for this topic.
You see, most modern shark jaws are sort of…hanging. They’re not completely detached, that would be silly, but they are not exactly fixed either. They are what are known as hyostylic – they have a cartilaginous attachment at the very back of the jaw but they’re sort of moveable. Try and jut your jaw out a little, say 5cm (about 2inches). You can’t do it, can you? That’s because your jaw-bone (mandile) is hinged, fixed to the rest of your cranium. Have you ever seen a great white taking a bite out of some bait? Notice how it projects its jaw out a little as it grabs at it. That’s the benefit of a hyostylic jaw. Instead of being fixed on a hinge like our jaws, it is attached at the back by loose, cartilaginous tabs.
Now the goblin shark, well that thing takes it to a whole new level. The goblin shark has specially adapted tendons on its hyostylic jaw that allow it to shoot its teeth out at prey. We know little about its hunting behaviours since it is a deep sea species that is rare to encounter, but it is believed to be a slow, ambush predator that, when prey comes into range…Thwoop! Throw your teeth at it, slingshotted by these incredible tendons, and snap them back.
It’s also such a deep-sea species its skin is semi-translucent, making it look weirdly pink. It is, as far as we know, the pinkest shark on earth – Weird.
I told you going into this, sharks are diverse! Back to the frilled shark though.
…A jaw attached to the cranium is known as an amphistylic jaw, and was common in prehistoric shark and fish species. It also possesses a ‘notochord’. Remember the phylum ‘chordata’ of which both cats and sharks (and all animals, really) are a member? Well the presence of this notochord is what designates a chordate. In many species this has evolved into the the vertebrae, the spinal column – a flexible line of discs down the back that house the main nerve – but that develops out of the notochord.
Well, the frilled shark has a cartilaginous, reinforced notochord! Not an actual spinal column.
What’s more it has six pairs of gill slits. Most modern sharks only have five but there are a few species that have seven, but six, that’s associated with more ancient sharks.
All of this, as is the wont of taxonomists, led to a lot of arguing and discussion about where and how to classify the frilled shark! It was an anomaly, a ‘living fossil’ in a seemingly very true sense of the word – not that those words mean anything.
The idea is that evolution tends towards ‘development’ and ‘complication’ but that’s bollocks. Evolution tends to survival and evironmental problem solving. That has led to many species that actively get rid of a ‘positive’ adaptation – take flightless birds, for example. The Ostrich found a niche for which it does not need flight to survive. To fit that niche it adapted out of its ability to fly, something that you’d be mad to not think of as a very positive adaptation. Still, Ostriches exist, they survive.
If it exists now, it has earned that right to exist just the same as every other species, in the same time, via the same process. There is no ‘primitivism’ in evolution – just what’s currently working and what’s dead. I don’t think this is emphasised enough in popular explanations of evolutionary biology, particularly when discussing things like ‘living fossils’ because the concept of something seemingly so ancient still being alive is so available to our brains we’d rather think of it like…a caveman in New York City than what it actually is – a form of life that figured out a way to survive without needing to change. It’s a success, is what it is. It’s a caveman in New York City named David Lieberwitz who wears a suit, works at a law firm and, besides his thickset brow and his propensity for telling people to “Ugg off!” when he’s annoyed displays no other sign of not being adapted to his current environment versus his peers.
Anyway, mercifully, these days, we have genetics to come along and help solve a lot of these arguments and studies indicate it is a member of the Hexanchiformes order (yup, it’s got a genus name that sounds like a sex disease and is in an order that sounds like construction worker red-tape “Hey Sandra, you fill out those Hexanky Forms? They need submitting by tomorrow!”), seven extant species of some of the most ‘primitive’ types of sharks around – represented by our two frilled shark species and five cow shark species.
As far as eating goes, well…what a mouth this has got on it! As if to add further frilling to the name its teeth are not arranged in a single line, rather they form rows in its mouth, somewhere around 20-30 on the lower jaw, of curved, tri-pointed teeth. It’s like mouth Velcro, it’s a trap and given it is suspected it can open its jaw quite wide it makes the reason a bit grim. It can eat quite large prey, possibly gulping it down like gulper eels, swallowing it nearly whole. It is believed to mainly eat squid species, smaller sharks and other fish, based upon the stomach contents of fished-up sharks. Squid seems to make up the majority (around 60%) of their diet.
Their breeding is also weird. They are ovoviviparous – that’s the fanciest word around for ‘lays eggs inside itself’. The young are encased in eggs but kept inside the mother, non-placentally, they are not attached like in mammals, so they feed off of yolk sacs that the shark develops until she is ready to give birth by pushing out the egg capsule.
Here’s the thing about frilled sharks, we don’t know an awful lot about them. We have figured a lot out about them, because we keep accidentally fishing them up. When you learn a lot about an animal because you keep accidentally killing it as a by-product of your overfishing you know you’ve got a problem.
How it actually lives, how it actually hunts, observing it in the wild, is difficult to do. Observing any underwater fish deeper than reef-level is a chore for us landlubbers, but the frilled shark has a tendency for going deep with 600-900m as not an uncommon depth for them to be found at. That they eat a lot of squid would suggest they migrate vertically, like a many squid do, up and down throughout the day following their preferred prey.
So, I can’t give my standard anti-human lecture here because we don’t actually know how many there are of it they’re threatened. The IUCN has it listed as least concern, at the same time we know they gestate and reproduce slowly, and we don’t know how many there may be out there.
In a list where my main aim for selection was to highlight the cuter, less threatening side of sharks I think the frilled shark stands out as anomalous but, that’s also why it’s here. It is unusual. It is, as far as I am aware, the only extant shark genus with that eel-like form. It highlights one of the other things I want to do with this list which is stop people hearing ‘shark’ and thinking ‘savage great white’ and get them, instead, to consider the vast diversity, the strange array and multitude of species and behaviours and structures and forms that the sharks represent.
Nah, it’s not cute. But I want to give it a hug anyway for teaching us so much, and changing our perceptions of what a shark can be, or is.
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#10 – The massive, magnificent megalodon – a prehistoric giant!
#9 – The beautiful and quick blue shark
#8 – Known for it’s spiral of jagged teeth, Helicoprion – the Buzzsaw shark!
#6 – The Great White, Apex predator, whale scavenger, more intelligent than we thought.
#5 – The Megamouth Shark – One that tells us more about what we don’t know!
#4 – The Graceful Hammerhead family – Much overfished, and is one a veggie?
#3 – The aparently philosophical basking shark! – Happy just existing.
#2 – The longest living vetebrate on earth – The Greenland Shark
We Lack Discipline 
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