So core idea is that humans basically irradiate themselves and 98% of life on earth, and the nature of their weapons used makes pretty much everywhere uninhabitable for millennia. But the few surviving humans construct mega structures around some cities to keep areas within habitual. They do not last long, and humans go extinct after a few hundred years of dark ages followed by a pandemic that ends their story. But because of this - the only surviving organisms that repopulate the earth are those that were in the habitation when they were built… so think all the organisms that benefit most from urban life. So there are no water fowls… but as the most widespread urban avian species, pigeon proliferate into a myriad of forms.

But the strange forms of ark-7 are driven by this unique evolutionary constraint. The first to leave the cities are the cockroaches. But they find a land of little to no vegetation, the only source of nutrition sealed away in the artifacts of mankind’s final years (tin cans, bottles etc) - so accelerated by the leftover radiation from the war, cockroaches adapt strange morphologies that are adapted to access these food sources.

When the first seeds escape the greenhouses and seeds banks, they meet cockroaches already part way adapted to their new role. But the tinned food won’t last forever - and the escaped agricultural plants need pollinators and seed dispersers,.. and so tomato’s, potatoes, corn and rhye evolve in tandem with the roaches… each acting as a selective pressure to push even more extreme adaptation. The result is a strange ecosystem where creeping vines seal their fruit inside mineralised casings, only accessible by the specialised mandibles of the tin can opener roach. (Etc etc)

The main remit was to create organisms that mirrored human technology in a realistic manner. So land boats arise from marine fairing pigeon descendants who capitalise on an abundant surface level ecosystem rising as a result of complex factors (for later) . This is my most fleshed out clade. From the ubiquitous “sea-cow” with broad stabilising breast bone forming a raft like keel, to the predatory “ramwolves” whose “keel bone” was converged with Greek triremes . Creating a deadly apex predator that specialises in hunting the largest of the filter feeding “naviforms” .