"By invertebrates are meant the non-vertebrate creatures of the kingdom Animalia (or Metazoa+b vmbnParazoa) in the biotic domain of Eukaryota. By phyletic definition, these many-celled, sub-vertebrate animals lack a vertebral column, spinal column, vertebrae, backbone, or long, full-length notochord -- in contrast, of course, to the vertebrates in the one phylum of Chordata."@en . . . "By invertebrates are meant the non-vertebrate creatures of the kingdom Animalia (or Metazoa+b vmbnParazoa) in the biotic domain of Eukaryota. By phyletic definition, these many-celled, sub-vertebrate animals lack a vertebral column, spinal column, vertebrae, backbone, or long, full-length notochord -- in contrast, of course, to the vertebrates in the one phylum of Chordata. Relatedly, invertebrates have never had a cartilaginous and/or boney internal skeleton, with its skeletal supports, gill slits, ribs and jaws. Finally, throughout geologic time, invertebrates have remained non-craniate creatures; that is, they never developed a cranium, nerve-chord brain, skull, or hard protective braincase."@en . . . . . "Invertebrate paleontology"@en . . . .