During embryogenesis, all members of this phylum have pharyngeal gill slits and a namesake tube of cartilage found below the neural tube.
Ernst Haeckel first applied the idea that "ontogeny recapitulates phylogeny" to members of this phylum. The Spemann organizer was discovered in an animal from this phylum. As embryos, members of this phylum form blobs of mesoderm called somites. In this phylum, cleavage is indeterminate but forms a body that is  never  radially symmetric. A morphogenetic gradient of (*)  sonic hedgehog patterns the AP axis in this phylum. Organisms in this phylum, like  Xenopus , have a blastopore that develops into the anus, making them deuterostomes, just like echinoderms. During embryogenesis, all members of this phylum have pharyngeal gill slits and a namesake tube of cartilage found below the neural tube. For 10 points, name this phylum that includes hagfish, frogs, and humans.
Ernst Haeckel first applied the idea that "ontogeny recapitulates phylogeny" to members of this phylum.
Chordata  [or  chordate s; do not accept or prompt on "vertebrates" or "Vertebrata"]