Through a mixture of developmental quirks and neoteny, the Stinzerstar split off from its ancestor and developed an amphibious lifestyle to feed on organisms which resided on land and in watersheds. To support itself, its lateral arms are modified to have the same 6-bone structure as its raptorial arm, granting it better leverage; this was easily accomplished as a result of its radially symmetric larval stage, and is in combination with partial neoteny to prevent its lateral fingers from fusing in adulthood. It retains its gills and the ability to swim with its webbed feet; the presence of its gills forces it to stay near water.
On land, the Stinzerstar is able to breathe easily thanks to it already possessing lungs. Its pre-existing “tongue” makes capturing and swallowing food on land not an issue. The greatest struggle it faced was its eyes drying out or being damaged by dust, but it avoids this using a ring of muscle around its eyes—an eyelid—to close them. It retains its crushing lateral mandible spikes, which are more effective on land than they were in water thanks to dry keratin being stronger than moist keratin, and it has a more reptile-like face better suited for capturing food on land while not being useless in water. To work around the bulky shape of its face, its lateral mandible bones, which were already connected to the upper and lower mandibles by a sliding joint, can be pulled nearly to the front of the snout, extending the corresponding spikes well beyond the reach of its main jaws; this even allows them to be used for prey capture, though that is not their primary function.
To help protect itself from desiccation, the Stinzerstar has tougher skin, which also contains more keratin. This isn’t perfect, and it must return to the water to soak; prolonged exposure to air has the potential to damage its gills, which are not adapted for use out of water. Still, this grants it an advantage which explains its broad adult range: it isn’t as sensitive to the different climate conditions throughout its range, as it can simply return to the water when conditions aren’t as favorable. The Stinzerstar’s teeth and lateral jaw spikes have bone cores, increasing their strength and usefulness.
The Stinzerstar’s terrestrial locomotion is an awkward 3-legged springing motion. While the anal arm is used to stand, it is not used for walking due to the vertebrae-like bone structure being poorly suited for that purpose. Its 3 legs are long, which helps with both the effectiveness of the Stinzerstar’s springing ability and its ability to spot predators, such as Arthrotheres, which could easily eat it.
Although adult Stinzerstars have the capacity to resist osmosis and retain salt for their biological functions, this is not well-developed in their offspring. As a result, the Stinzerstar had to find a unique solution to raising its young. Adults travel downstream to the nearest beach to mate, and they give birth in tide pools. As the tide pools can be a dangerous place during high tide, the newborn larvae are larger and have fully-developed eyes and their nostrils already placed at the ends of their snouts. Both parents bring food to their offspring from further inland until they’ve metamorphosed enough that they can swim effectively, at which point the offspring leave the tide pools and wander the ocean floor on their own. When fleeing predators or chasing prey, they may also swim in the open waters; they are capable of doing so long enough that they can return to the shallows afterwards, which allows them to live on both sides of the sea. Near adulthood, they develop salt retention and move into land and freshwater, never to return to the ocean again until they also mate.
To support larger, better-developed young, as well as pregnancy on land, the Stinzerstar has developed a more advanced reproductive system. In females, this consists of two ovaries and a larger uterus which closes off during pregnancy, while in males this consists of 3 internal testes; the uterus and middle testicle are homologous, making it a sort of 3-lobed reproductive organ in both sexes. This change also allowed more efficient sperm production in males, and it allowed females to more effectively retain and incubate the fetuses.
The Stinzerstar, like most lagnodactyls, mates by holding hands—the membrane on its anal arm can be pulled back to reveal the anal fingers which are used in this. Its babies, aside from their sensory organs, appear radially symmetric and develop other bilateral traits as they mature.