This would have allowed them to live as active predators of other invertebrates in the early Palaeozoic seas, which by modern standards were severely hypoxic; the Earth's atmosphere at that time probably contained less than 10 per cent oxygen. (newscientist.com)
Overall, however, gene family sizes in octopuses are largely similar to those found in other invertebrates. (uchospitals.edu)
Centipedes are carnivores that feed on other invertebrate animals. (sciencedaily.com)