Meet Aquatoxin Scizor, the result of a recolour as Qwilfish laced with Muk
Though Kabutops in its day was a mighty hunter, it struggled to adapt to new surroundings, especially the abundant plant life in the jungles which began to emerge as time went on. Those who survived were those who were different; those with an innate resistance to the attacks of the many plants which were found in these new areas. While the more successful and abundant developed the characteristics of bugs, even to the point of wings emerging, others were better adapted to surviving in swamps by defending themselves with a form of poison. This sub-species which found itself better suited to living under the water, and centuries of living there caused its body to gain a more round shape better suited to aquatic living, and its formerly long scythes developed into claws laced with venom, and where its grassland counterpart gained wings, similar appendages emerged to be used more like fins. Though a rare species, this is a beast the jungle wanderers dread encountering.
You will all accept my headcanon that Kabutops evolved Darwin-style into Scyther.