Invertebrates
The term invertebrates corresponds to the phylogenies Porifera, Cnidaria, Ctenidores, Platyhelminthes, Nemertea, Gthathostomulida, Rotifera, Annelida, Pogonophora, Sipuncula, Echiura, Priapulida, Pentastomida, Onycophora, Tardigrada, Arthropoda, Monoblastozoa, Trilobozoa, Archaeocyatha, Proarticulata and the three subfiles of the chordata of the Chordates: Urucordados, Cefalocordados and Hyperotreti, that includes the mixinas or witch fishes. The term invertebrates is scientifically correct, it does not mean all those beings that belong to the Vertebrate subphylum, that is, they are not beings endowed with notochord, neural tube with dorsal position in relation to the digestive tube, and gill pits at pharyngeal level. The difference is that in Invertebrates, the notochord is replaced or framed in a structure denominated vertebral column, hence the name Vertebrates. The opposite term - Vertebrates - already has a biological meaning, since all its representatives, mammals, birds, fish, reptiles, amphibians and synapsids are related, that is, they all have a common ancestor.