Sentrok
Split off from the Spectacled Arthrothere, the Sentrok has begun to use its forelimbs to manipulate food rather than its antennae. It does this because they are better positioned to pick up food from the ground; the antenna claws had evolved in ancient aquatic ancestors that grabbed prey above them, but they made far less sense for a land-dwelling creature. This is also because the forelimbs are significantly stronger than the antennae and have more digits, allowing the Sentrok to use them to pull flora out of the ground. It uses its strong, triangular beak to break into small crystals, like many terran birds which eat similarly hard foods.
Rather than reduce its antennae, the Sentrok has modified them to be more useful as sensory organs. A small number of whisker-like filaments cover them, allowing it to feel up and investigate an object in its hands—or a potential mate. This helps to give it a better idea of what it’s examining and properly identify it as friend, fiend, or food if it isn’t clear on sight. It has developed an ability to feel itches and an instinct to scratch, helping it to remove Wormrot before it begins to eat away at its carapace; as a result, it is mainly weakened individuals which fall ill.
The Sentrok has re-thickened parts of its exoskeleton to support its muscles, as a thin exoskeleton is just as detrimental to survival as weak bones in any other organism. The thickened parts mainly include parts where important muscles attach, as these portions of the exoskeleton are under the most pressure and are therefore more likely to break during strenuous activity if they are not reinforced. This also gives it a significant speed and energy efficiency advantage over its ancestor. Its vestigial fins have also increased in size, allowing them to be used as a health indicator while selecting a mate.
The Sentrok is otherwise much like its ancestor. Its facial markings play a role in mate selection, its erect posture is supported by “vertebrae” under its exoskeleton, and it is ovoviviparous.