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Cake day: June 10th, 2023

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  • It is certainly a challenge to keep a large animal with such a thick shell afloat. However that would just explain the immense size of the shells. Their shape is just extremely weird and sometimes I’d even expect it to be detrimental to their ability to navigate the open water. If they were planktonic it would not be as problematic I guess but I still don’t see the functional advantage. Maybe mimicry? But of what?

    They look a lot like the calcareous shells of some polychaetes but they have a sedentary lifestyle attached to rock or other substrates which is not what we’d expect for Ammonites.

    Maybe it’s a puzzle that will remain unsolved.














  • More likely the small size, flight and the holometabolous lifestyle.

    There is the theory that the number of species is related to the number of available niches. For mammals, a tree may offer 2-3 with the ground, the branches and maybe something like burrowing (this is just for illustration purposes).

    Insects can live in the leaves, dead branches, inside the wood, in the mosses, on the ground, in the leaf litter layer, burrowing etc., etc. because they are so small. They can also easily transit between different places because most of them can fly.

    Because the larvae of holometabolous insects can occupy a completely different niche than the adults, every combination of niches can more or less be considered a new niche.

    All of this is reflected in the species richness of insects. The primary wingless groups of insects are not very diverse compared to winged insects. And within the winged insects, the holometabolous species make up the vast majority. Hymenoptera, flies and beetles make up the majority of insects and they are all winged and holometabolous. If you just look at the hemimetabolous ones, they aren’t much more diverse than other groups of arthropods.