Squid Island Longjaw
With no competition from other herbivores on Squid Island, as well as a complete lack of predators and plentiful, verdant bounty of crystal flora upon which to feed, the Squid Island longjaw has come to dominate its new landscape. Splitting from its ancestor, this now herbivorous descendant has nearly quadrupled in size, though it retains its stocky frame in order to support its weight on land. They have continued the trend of their lineage of adapting to a terrestrial existence, with the multi-chambered sac serving as a sort of pseudo-lung allowing them to remain on land almost indefinitely. As such, they only need to drink once every several days in order to replenish their water supplies and thus prevent desiccation.
Just as its name suggests, this species has evolved an elongated jaw with which it uses to pick individual crystals from forests of crystal flora that envelope the island. They snap up these crystals, crunching through their photosynthetic chitinous shells in order to reach the juicy fungal-like cores within. Rows of blunt chitinous teeth within help to achieve this. The end of the jaw has evolved a hardened, serrated edge, like a beak, with which they use to bite off the crystals from their roots, as well as take chunks out of larger ones. Smaller crystals, meanwhile, are instead typically swallowed whole and relatively intact. The longjaw's digestive system has become more efficient at breaking down and digesting the crystal flora.
With no predators, the longjaw could afford to become more colorful. They display these bright colorations to one another in order to display their health, thus the healthier one is, the more vibrant its colors are. Males in particular will use this when competing with one another for mates, instead of resorting to violence.
While adults dominate Squid Island, the young instead remain in the water. Once they've developed enough within the egg chamber, they are released into the water where they will continue to grow for several weeks. During this time, they will, like the young of their ancestors, feed primarily on the corpses of larger organisms and small bits of detritus. They will, however, also incorporate small species of crystal flora into their diet, such as the caltrop crystals. Once they have reached about 10 cm in length, they will emerge from the water and take to the land. From this point on, should they manage to avoid dying - a fairly simple task given the conditions of the island - they can live to be nearly half a century old.