The tetrapod whorl split from its ancestor the grand whorl. It has spread further west and co-exists with its ancestor. Like its relative the river pod-whorl it has changed its life cycle and now most of its life stays at the pod state and will only hatch when it is an adult and breeds and spreads its spores. For the first one and a half years it will grow as a four legged pod filtering through its nets and breathing in through its main hole and out through its tubes. When it will reach its maximum size it will hatch and a full grown adult will swim out. This adult is quite similar to its ancestor only it can grow much larger, has a slightly different spike spread, and a different coloration. This adult will then swim for half a year and feed in order to grow to maximum size, and then migrate as far as it can. When its around two years old its bodily functions would slow down, it will dig itself into the ground, and eventually die. From its corpse newly borne spore will be released. Some will be spread by predators that feed on the corpse, others from the shell itself, and some will be spread by the currents.