ABSTRACT
Vertebrates began their transition to land during the late Devonian Period about 375 million years ago. Over a span of 15 million-years, a mosaic of changes remodeled the fish skeletal design to accommodate new modes of locomotion, feeding, and sensory input for life on land. All land vertebrates are formally called tetrapods in reference to their two pair of well-developed limbs. Tracing the history of the earliest tetrapods and their descendants has always been difficult, and several taxonomic names have been applied to various groups
The amphibians of today belong to a lineage called the Lissamphibia, commonly known as the salamanders (Caudata), frogs (Anura), and a more obscure group, the caecilians (Gymnophiona). Lissamphibians bear little resemblance to the earliest tetrapods, and in their own right are quite specialized structurally, ecologically, and behaviorally.
In Southern California 12 species of salamanders are distributed among three families: (1) Ambystomatidae (mole salamanders), (2) Salamandridae (newts), and (3) Plethodontidae (lungless salamanders). As with salamanders, anuran species diversity is rather limited in the arid Southwest. Southern California hosts 17 species of frogs in five families. They include jumpers, hoppers, climbers, swimmers, and burrowers: (1) Pelobatidae (spadefoots), (2) Bufonidae (toads), (3) Hylidae (treefrogs or chorus frogs), (4) Ranidae (“true” frogs), and (5) Pipidae (introduced African Clawed Frog).
Worldwide, amphibian species have been declining at an alarming rate.
