When some Arctic legobox spores were carried off to the warm seas of the south, they were met with a veritable abundance of potential meals in the form of Insects Which Must Logically Exist to Maintain a Biosphere. It indeed seems obvious that these legobox populations would quickly evolve to take advantage of this bounty, and so they did - spawning the Mimic Legobox.
The Mimic Legobox is so named for the twin tentacle-like protrusions growing on the margins of its lid, “cleverly” imitating a pair of tasty poralps. It spends much of the time hunting situated within the substrate - out of its preys’ sight, which it could easily dig into and out of utilizing rapid movements of the cirii on its corners. Prey chemical signatures are detected via a “mustache” of sensory setae rimming the mouth of its lid, and once it has gauged that its duped meal is within close proximity, the Mimic Legobox swiftly flips its lid open, creating a sucking current powerful enough to heave the unfortunate prey inside, by which the legobox seals its lid shut and prepares for digestion. While its lid is still open, it may passively consume microfauna, and is large enough to not quickly succumb to spite-bearing organisms.
In response to this abundance of food, the Mimic Legobox is much larger than its ancestry.
To ensure further eventual diversity, Mimic Legoboxes - in times of abundance - shed copious volumes of gametes into the water, many of which will conjugate to become spores, then settle onto the substrate to develop into larvae.