Human beings are chordates—of the phylum chordata—and so are all other vertebrates, or animals with a spinal column. In addition, there are two invertebrate groups of chordates: the urochordates and the cephalochordates. The Urochordata...

Chordates are animals in the phylum Chordata. At some stage of their development, all chordates have the following characters: a notochord, gill slits, a dorsal hollow nerve cord, and a post-anal tail. There are three sub-phyla of chordates: the...

Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. They are united by having, at some time in their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal...

Looking something like a tiny squashed eel, a newfound fossil from southwest China will not win any beauty contests. Yet this 530-million-year-old specimen from Earth's Cambrian period holds a special allure for paleontologists. It may be the oldest known chordate, the phylum to...

INTRODUCTION UNTIL RECENTLY, our understanding of the earliest history of the fish has been fragmentary in terms of the fossil record and conjectural with respect to many details of phylogeny. Fortunately, significant new information has become available in recent years, most notably from...