Okay yeah so theyre not dinosaurs but i thought it would be cool to have like a race that evolved from dinosaurs AND a race of like mushroom elves. I feel like movie bowser definitely encourages the other dino folk to see the mushroom people as lesser. maybe they were native to the mushroom kingdom before the koopas moved in and built the city over it.
To that end I think the de-volver machine just turns them into a more animalistic neanderthal-y version of themselves. The spike collars are how bowser controls the goombas when they get out of line.