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Invertebrate montage (2022).jpg

Invertebrates is an umbrella term describing animals that neither develop nor retain a vertebral column (commonly known as a spine or backbone), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum Vertebrata, i.e. vertebrates. Well-known phyla of invertebrates include arthropods, mollusks, annelids, echinoderms, flatworms, cnidarians, and sponges.

The majority of animal species are invertebrates; one estimate puts the figure at 97%.

From Wikipedia