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).
By the late Devonian, 360 million years ago, early cartilaginous fish and bony fish were diversifying. The late Devonian also marked the first tetrapods -- vertebrates with true legs that could walk on land. By about 330 million years ago, in the Mississippian, several groups of land-dwelling amphibians had appeared.The oldest known amniotes -- close to the ancestry of all reptiles, birds, and mammals -- appeared in the early Pennsylvanian, about 310 million years ago.ut to give a very brief summary: The first known vertebrate fossils, found at the Chengjiang locality in China, date back to the early Cambrian. These early vertebrates, such as Haikouichthys, are small, tapered, streamlined animals showing eyes, a brain, pharyngeal arches, a notochord, and rudimentary vertebrae.