A chemical formula contains information on the types and spatial arrangement of bonds in the chemical. It also tells you what elements are in the chemical, and how many atoms of each. The spatial arrangement is not necessarily very obvious from the formula, e.g. C2H5OH does not tell you much about the spatial arrangement of the bonds. A chemical formula contains information on the types and spatial arrangement of bonds in the chemical.
All modern amphibians are included in the subclass Lissamphibia, which is usually considered a clade, a group of species that have evolved from a common ancestor. The three modern orders are Anura (the frogs and toads), Caudata (or Urodela, the salamanders), and Gymnophiona (or Apoda, the caecilians).
The most basal group of vertebrates are the Hyperoartia (lampreys) which survive as disgusting, but rather interesting, blood-sucking parasites on fish. In addition, the vertebrates produced the Euconodonta, the Pteraspidomorphi, and a vague, perhaps polyphyletic group referred to for the time being as  Thelodonti .ork on what is now the vertebrates section of Palaeos began less than five years ago [ ed. note-this was written in 2001 - MAK111022]. At that time, the consensus view of early vertebrate evolution was not far from the cladogram reflected when the predecessor to this site first went on line.