Size of some coconut crabs
Size of some alligator gar fish...found in American lakes
The eggplant got its name because the first ones looked like this
Full picture of the tianamen square tank protester
some octopuses possess the foresight to actually pack along coconut shells to use as protective shelters when exploring areas without adequate places to hide.
The reason public toilets have the gap in the front of the seat (there are other reasons out there too)
Warning: Spoiler! (Click to show)
circular-shaped objects have rigidity based on their form. This means they resist deformation when force is applied (your *** sitting on toilet seat). This can be a good thing: Toilet seat feels structurally sound when sitting on it.
The problem is that the rigidity is not infinite. There is a snap point, and since the form is not able to bend, when the snap point is hit, it usually fails VERY BADLY. In our case, this often means replacing the toilet seat ($$$).
By taking a very small wedge out of an otherwise full circle, it changes the whole dynamic of the form. All of a sudden we have a U shape instead of an O. Now, both "legs" of the U are able to (mostly) independently move. This raises the "snap point" as the materials are now able to bend effectively and more thoroughly distribute load.
At the end of the day, the shape choice of a toilet seat is about it's reliability. In normal usage, U shaped seats are MUCH less likely to break over the long term than O shaped seats.
And at the end of the week, reliability is really about money. How long will thing X last given normal use conditions? When will I have to replace it? What are the costs associated with wear and tear? This makes sense in the context of businesses/governments (who usually own the public toilets in question here).
The reason that they are different at home is because at home you also (usually) have aesthetic requirements that automatically trump any cost related requirements. This is due to a combination of (a) people liking to surround themselves with things that are pretty, and (b) home toilet seats get very light use compared to public toilet seats and therefore are (by default) much less likely to fail at any given point in time.