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).
But that's not what Gregory Retallack, a geologist at the University of Oregon, thinks. Instead, Retallack argues that that the very first landlubbers belonged to an extinct group of organisms called Ediacara, which last lived on Earth some hundred million years before the rise of amphibious plants. The Ediacara's lack of living ancestors makes it a hard group of organisms to learn about.