Source: cirosantilli/vertebrate
= Vertebrate
{wiki}
The big breakthrough of the vertebrates appears to be the ability to swim around in a straight line and eat smaller species that are floating about.
<Bones> appear to help that a lot!
It is likely the most efficient design to travel long distances. Be thin and wiggle your tail around.
Perhaps smaller <animals> can skip the bone thing. Maybe a notable example are the <lancelets>, which look a bit like small fish. But they only go up to 8 cm.