A toad is any of a number of species of amphibians in the order Anura (frogs) characterized by dry, leathery skin, short legs, and snout-like parotoid glands A distinction between frogs and toads is not made in taxonomy, but is common in popular culture, in which toads are associated with drier skin and more terrestrial habitats than animals commonly called frogs In taxonomy, toads are found in the families. A group of toads is called a knot. The bumps on a toad's skin help the animal to blend into its environment visually by breaking up its outline. And, although the parotoid glands are often mistaken for "warts", they are present on healthy specimens and are not a result of infection The true toads are the family Bufonidae, members of the order Anura (frogs and toads). They are the only family of anurans in which all members are known as "toads". The bufonids now comprise more than 35 genera, Bufo being the most widespread and well known. True toads are widespread and are native to every continent except Australia and Antarctica, inhabiting a variety of environments, from arid areas to rainforest. Most lay eggs in paired strings that hatch into tadpoles, although, in the genus Nectophrynoides, the eggs hatch directly into miniature toads. True toads are toothless and generally warty in appearance. They have a pair of parotoid glands on the back of their heads. These glands contain an alkaloid poison which the toads excrete when stressed. The poison in the glands contains a number of toxins causing different effects. Bufotoxin is a general term. Different animals contain significantly different substances and proportions of substances. Some, like the cane toad Bufo marinus, are more toxic than others. Some "psychoactive toads", such as the frog frogs toad toads hunt hunts predator predators fish fishing teenage mutant ninja turtles turtle soup food eat eating cook cooking cooks eats prepare prepares preparing recipe animal animals amphibian amphibians reptiles reptile school education national geographic world nature natures funny cute weird adorable pet pets green snapper snappers attack attacks danger dangers dangerous swim swims swimming swimmer swimmers sea ocean lake lakes water waters pond ponds salamander salamanders Colorado River toad Bufo alvaris, have been used recreationally for the effects of their bufotoxin. Male toads possess a Bidder's organ. Under the right conditions, the organ becomes an active ovary and the toad, in effect, becomes female The first major groups of amphibians developed in the Devonian period, around 370 million years ago, from lobe-finned fish similar to the modern coelacanth and lungfish which had evolved multi-jointed leg-like fins with digits that enabled them to crawl along the sea bottom. Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required. Eventually, their bony fins would evolve into limbs and they would become the ancestors to all tetrapods, including modern amphibians, reptiles, birds, and mammals. Despite being able to crawl on land, many of these prehistoric tetrapodomorph fish still spent most of their time in the water. They had started to develop lungs, but still breathed predominantly with gills was one of the first primitive amphibians, with nostrils and more efficient lungs. It had four sturdy limbs, a neck, a tail with fins and a skull very similar to that of the lobe-finned fish, Eusthenopteron. Amphibians evolved adaptations that allowed them to stay out of the water for longer periods. Their lungs improved and their skeletons became heavier and stronger, better able to cope with the increased gravitational effect of life on land. They developed "hands" and "feet" with five or more digits the skin became more capable of retaining body fluids and resisting desiccation. The fish's hyomandibula bone in the hyoid region behind the gills diminished in size and became the stapes of the amphibian ear, an adaptation necessary for hearing on dry land. An affinity between the amphibians and the teleost fish is the multi-folded structure of the teeth and the paired supra-occipital bones at the back of the head, neither of these features being found elsewhere in the animal kingdom. The Permian lepospondyl Diplocaulus was largely aquatic At the end of the Devonian period (360 million years ago), the seas, rivers and lakes were teeming with life while the land was the realm of early plants and devoid of vertebrates, though some, such as Ichthyostega, may have sometimes hauled themselves out of the water. It is thought they may have propelled themselves with their forelimbs, dragging their hindquarters in a similar manner to that used by the elephant seal. In the early Carboniferous (360 to 345 million years ago), the climate became wet and warm

• published: 03 Apr 2014
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