Frogs and Toads

Frogs and toads belong to the order Anura. Anura means tailless amphibian. There are three smaller orders and they are Caecilian (Apoda), sirens (Trachystomata) and salamanders (Caudata). These are all classed as amphibians. The early amphibians were the first vertebrates to give up aquatic existence and begin the colonisation of the land about 350 million years ago. However, the frogs and toads didn't appear for another 200 million years. Amphibians still have a very close relationship with water as they have glandular skins which must be kept slightly moist and most of the different species return to the water to lay their eggs. These then develop into aquatic gill-breathing larvae, or tadpoles, before then developing into the terrestrial stage of their lives.

Just out of interest, the word 'amphibian' derives from two Greek words: 'amphi, meaning 'both' and bios meaning 'life'.

What is the difference between frogs and toads? This is a very often asked question about these creatures. It is also a difficult question to explain. It is best to remember that when these two words were 'invented' there were only two sorts of anura that were recognised, those being the frog, later known as Rana temporaria, a moist, slimy creature that jumped, and the toad, Bufo bufo, which was dry and warty and also walked. Gradually, as more and more of these species came to be found in other areas, the two names ie frog and toad, were applied to them according to their resemblance to one or the other 'frog' or 'toad'. This was fine to begin with, but as more species were found, some of them bore resemblance to both the frog and the toad, having both moist, slimy species that also had dry warty relatives! Things are never simple in nature! It can be helpful to think of tailless amphibians as 'frogs'. We do not really know an awful lot about the living frogs and toads, but our knowledge of their ancestors is even less! However, it is commonly believed that amphibians evolved from a group of fish known as lobe-fins (crossopterygians) which lived during the Devonian period which was approximately 350-400 million years ago! It does seem most likely that the earliest amphibians evolved in shallow fresh-water lakes. Fossils of the oldest amphibian come from Greenland and were formed at the end of the Devonian period, which was about 350 million years ago (roughly!!).

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