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Animal, Vegetable or Mineral? Mystery Egg 2

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Time for blog post number 2 in the Booth’s Mystery Egg series for Easter.

Having worked at the Booth Museum for several years, I have seen a lot of really bizarre objects behind the scenes, some of which I have taken photos of and others which are just stuck in my mind’s eye. Normally, I would bring these objects out from behind the scenes to show visitors at the museum, but, under the current circumstances of Covid-19, we thought we would do three special additions of our usual Animal, Vegetable or Mineral? quiz online to show you some unusual animal eggs, made by some pretty incredible animals.

These are all objects we have behind the scenes at the Booth Museum! Here is Mystery Egg number 2 of 3, look out for the last one over the next few days.

Mystery Egg 2

Mystery Egg 2, Photwik / CC BY-SA (

Clue 1

These cork-screw shaped egg cases get washed up on the beaches of Australia, but if you haven’t been lucky enough to visit the sunny beaches down-under, you might have seen similar egg cases washed up on the exotic beaches of the UK (like the one pictured below). The animals that produced these egg cases or ‘mermaids purses’ in UK waters are related to the animal that made Mystery Egg case 2.

Mermaids purse, Evelyn Simak

Clue 2

The ocean-dwelling creatures that have made these eggs have a reputation for being formidable killers and top predators, some might even say they are mindless killing machines



…and who can blame people for thinking this, when faced with a set of razor-sharp teeth like these…

Clue 2 animal teeth, Richard Ling from NSW, Australia / CC BY-SA (

And the answer is… Drum roll please!

The Port Jackson shark, Heterodontus portusjacksoni.

Ok, these teeth might have thrown you a little, but the Mystery Egg for today belongs to a species of shark. There are more than 440 species of shark in the world and our Mystery Egg belongs to the Port Jackson shark, Heterodontus portusjacksoni. 

Mark Norman, Museums Victoria / CC BY 4.0 (

These unlikely looking sharks live in Southern Australian waters and are found on the bottom of rocky, muddy or sandy environments or where sea-grass grows. One famous location in which they are found is Sydney Harbour, their common name Port Jackson, comes from the habour’s true geographical location. Port Jacksons can grow up to 2 metres in length and are known to migrate over 500 miles. They are incredible navigators and gather in huge numbers at the same spot every year in order to breed.

Not the typical eggs

The extraordinary spiral-shaped eggs are laid by the females two weeks after breeding. Each female lays two eggs and they are around the same size as the female’s head! Can you imagine how much energy it takes to make two eggs the size of your head? Well, it’s a lot! That’s why Port Jackson sharks are some of the best known mothers of the shark family. They carefully place an egg in their mouth and carry it around until they find the perfect rock crevice to wedge it into, to hide it away from predators. The spiral shape of their eggs makes them really difficult for predators like the crested hornshark to remove. These sneaky predators look almost exactly like the Port Jackson, which is why the eggs need to be hidden out of sight.

Not the typical teeth

I don’t know what you think, but when I think shark teeth, the Port Jackson’s aren’t typically what comes to mind. Their teeth are specially adapted to feed on their favourite meals, including sea urchins, molluscs, crustaceans and fishes.They have two distinct shapes, to enable them to feed on these animals, pointy at the front and flat at the back. The pointy front teeth are used for holding and breaking their prey and the back teeth are used to crush and grind hard shells. Their linnaen name Heterodontus comes from the Greek heteros meaning ‘different’ and dont meaning ‘tooth’.

Not the typical shark!

In order to breathe, most sharks need to move and keep their mouths open, this forces water over their gills to give them the oxygen they need. Port Jackson sharks are pretty unusual, in that they can eat and breathe at the same time. This means they can sit for long periods of time on the ocean floor without having to move, unlike many species of shark.

Sharks are one of my all time favourite animal groups, they are so varied in their behaviour, shape and form they are beautiful animals and are not the mindless killing machines that have been portrayed in the past. There are only a handful of unprovoked attacks on humans each year and around 6 related deaths, whereas humans kill around 100 million sharks each year. We are really lucky in the UK to have around 40 incredible sharks species that either live in,  or visit our waters including the gentle basking shark.

To learn more about how you can protect these wonderful animals visit the Marine Conservation Society Save our sharks.

You can see and touch the tooth from a Megalodon, an ancient giant shark, whose teeth were the size of a child’s hand, in the Booth Museum when we re-open.

Grace Brindle, Collections Assistant