Fish facts & theories

Fish Features

  • How big is the fish?

    It is estimated that it could be up to 16m in length, our specimen is thought to be 9m.

  • What fish living today is it most similar to?

    In lifestyle, the whaleshark.

  • What speed would it swim at?

    We can calculate its speed from the tail that has been found, and the length of the whole animal. So we can say that our Leedsichthys is likely to have had a steady swimming speed of 1.6 metres per second.

  • Could it swim backwards?

    There are very few types of fish that can swim backwards – most instead rely on turning. Our fish would have needed a turning circle of almost three metres in diameter!

  • What volume of water could it move with a single swish of its tail?

    Just over 4 cubic metres of water in one sweep to a side, double for the full action.

  • How big were its eyes?

    We believe its eyes would have been very large, as they are in other members of the family, but we have not found any of the sclerotic bones with which we could estimate the size of its eyes.

  • What colour were its scales?

    We don’t know, as its scales have not ever been preserved

  • What do we think it ate?

    We are confident that it ate plankton – and we also have some indications that our Leedsichthyscould also eat shellfish like ammonites.

  • Did it have teeth? If so, how many sets in a lifetime?

    Our Leedsichthys is the first to show any teeth at all – it would have had one set (of 4 teeth on each upper jaw) for its entire life.

  • Did it have vocal chords, or a similar way of making voluntary sound? Based on the fact it was found locally, would it have had a Peterborough accent?

    As vocal chords work in air, it would not have had them. The only sound that it is likely to have made is if it was feeding at the surface, and accidentally took in air. It may then have generated a small ‘fish-fart’ as the bubbles leaked out when it went underwater… Given that it traveled the world, it is unlikely that it would have had a strong local accent, anyway, even if it could have made voluntary noises.

Fish Behaviour

  • Would it have poked around for food with its nose like a bottom-feeder, or was it a mid-swim hunter?

    We have evidence that Leedsichthys could ingest food other than plankton, and is likely to have switched, seasonally to other sources. So there are remains of a large Jurassic seabed outside Basel in Switzerland with large feeding troughs in it, that have a sinusoidal pattern that reflects the movement of a fish swimming across the seabed with its mouth open and taking in the surface sediment.

  • Is it a girl or a boy?

    It is usually very hard to tell gender in fossil animals – especially fish. The way that palaeontologists normally recognise this in extinct animals is when they can compare a lot of different individuals, and see two very strong patterns amongst the remains. Usually these would be display structures, as with crested dinosaurs. Unfortunately, we have very few specimens where there are duplicate bones that we can compare between skeletons. The only exception is that we have two maxillae – and where one bears large crushing teeth, the other one is completely smooth. That could be a difference between males and females, but it is not the sort of characteristic that we would expect to distinguish them.

  • Did they lay eggs or have live birth fish

    Although as a fish you would expect it to lay eggs, this may not have been the case. The cartilaginous fish called the whale shark holds its eggs inside until the young hatch, and they swim out – ovoviviparity, sort of like a combination of both options – and as a similar-sized fish with a similar lifestyle, under similar pressures, it would not be surprising if Leedsichthys had a very similar solution.

  • What type of scavengers ate our fish when it died?

    We have examples of the teeth of small sharks called hybodonts, scattered throughout the animal’s remains, so it is fairly safe to assume that they scavenged extensively. However the body also looks to have been torn apart a bit, with large bones being moved far from the centre of the remains, so probably larger sharks, and maybe marine crocodiles could have been responsible for this. Peterborough Museum has another specimen of Leedsichthys that shows a skull bone with an embedded marine crocodile tooth in it, which would have come from scavenging.

  • Is it likely it was a loner, or lived in a school/flock/herd?

    Large planktivores tend to follow the same chemical traces to find and feed on plankton, so they tend to move in large groups.

  • How did our fish die?

    We have not found any traces of a life-ending attack on its body – no large bite marks, for example – so it may simply have succumbed to disease.

  • Do we know its likely life expectancy?

    We know from growth rings in its bones that our specimen, Ariston, was around 23 years old when it died, but we know of larger specimens of Leedsichthys that lived to more than 50 years old.

  • Was it local, or do we think it had a large territory?

    Large plankton feeders today – like the whale shark – are ocean going cruisers that circumnavigate the globe, moving from feeding patch to feeding patch. It seems very reasonable that a Jurassic large planktivore like Leedsichthys would have done the same thing – although the world that it traveled around would have looked very very different to today’s world.

Our Fish

  • Does our fish have a name?

    The name given to it during the dig was ‘Ariston’, because the bones kept going on and on and on. It’s a reference to a 1987 TV advert for washing machines.

  • How many boxes of bones are there?

    There are about 60 boxes of bones, however some of the bones are just too long to fit in a box, so we have about 20 large bones stored separately.

  • Does anyone else have a Leedsichthys?

    There are other museums around the world that have more fragmentary specimens than ours – in Cambridge, London, as well as in countries like the USA, France and Germany.

  • What is the collective noun for this fish?

    The collective noun for Leedsichthys is a ‘chaos’ of Leedsichthys, reflecting the fact that the remains of a single individual are not easy to interpret, but several together are extremely complicated.

  • What is the Plural of Leedsichthys?

    As it is a classical Greek word, you would show that it was plural by saying ‘many Leedsichthys’ – or a collective noun like a Chaos of Leedsichthys.

  • What dinosaurs were its contemporaries?

    Dinosaur remains from this time in the Jurassic are quite rare (there are quite a few found in China), but the giant sauropod dinosaur Patagosaurus from South America lived at the same time, as did a stegosaur called Lexovisaurus. In fact, several of the bones of Leedsichthys are so large, that they have been mistaken at different times for bones of Lexovisaurus.

Fish Fun

  • Could a trapped human escape through the gills pre-swallow? Could it eat a person and have someone live in its belly like in Pinocchio?

    People have theorised that this would be possible for people with today’s whale sharks, so it might be possible with Leedsichthys – it would be a risky thing to attempt, though! In terms of Pinocchio, I suspect it is unlikely that anything could have survived inside it – and there were certainly some long pieces of fossilised wood found amongst the remains of our specimen!

  • What would it taste like to eat?

    Probably closer to shark than salmon, given much of its skeleton was cartilage.

  • If it was in competition with a whale and a dolphin, who would win a race?

    A humpback whale’s top speed is around 27km/h and a bottlenose dolphin has a top speed of around 35km/h, our Leedsichthys is calculated to have a top speed of just over 30km/h. So our Leedsichthys would come second in such a race.

  • If one were to go fishing for this particular Leedsichthys, how strong would your rod and line need to be?

    It is fairly safe to say that at around 7,000kg in weight, you would struggle with even an ‘ultra heavy’ rod!

  • What size fish tank would I need to keep it as a pet? Do you have any tips for successful pet ownership such as amount of food and water temperature?

    To humanely keep Leedsichthys would be very difficult, without having your own sea, given their requirements for plankton, and their ocean-going lifestyle in the wild – this is one of the reasons why it has proved so difficult to keep whale sharks alive in aquaria today. Your personal sea would need to be around 20-30 degrees centigrade (the temperature of the Oxford Clay sea), and it would need to have enough depth of sea water and surface area to be able to support a large plankton population. Ideally, a healthy river supplying lots of nutrients nearby would be key to this.