A true toad is any member of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Bufonidae, in the order Anura (frogs and toads). This is the only family of anurans in which all members are known as

toad Toad (also known as a hoptoad) is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands. In popular culture (folk taxonomy ...

s, although some may be called frogs (such as harlequin frogs). The bufonids now comprise more than 35 genera, '' Bufo'' being the best known.

History

Bufonidae is thought to have originated in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. Some studies date the origin of the group to after the breakup of

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

, about 78–99 million years ago in the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

. In contrast, other studies have dated the origin of the group to the early Paleocene. The bufonids likely radiated out of South America during the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

, with the entire radiation occurring during the Eocene to Oligocene, marking an extremely rapid divergence likely facilitated by the Paleogene's changing climatic conditions.

Taxonomy

The following phylogeny of most genera in the family is based on Portik and Papenfuss, 2015:, Chan ''et al.'', 2016, Chandramouli ''et al.'', 2016, and Kok ''et al.'', 2017 '' Ingerophrynus'' alongside '' Leptophryne'' was grouped as basal to the clade containing all other

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

n toad genera and '' Ghatophryne'' by Portik and Papenfuss, but was found to group with '' Phrynoidis'' and '' Rentapia'' by Chan ''et al.'' ''Ghatophryne'' was grouped with ''Phrynoidis'' and ''Rentapia'' by Portik and Papenfuss but was found to group with '' Pelophryne'' and '' Ansonia'' by Chan ''et al.'' In addition, '' Sabahphrynus'' was grouped with '' Strauchbufo'' and '' Bufo'' by Portik and Papenfuss but was found to group with ''Pelophryne'', ''Ansonia'', and ''Ghatophryne'' by Chan ''et al.''

Characteristics

True toads are widespread and are native to every continent except

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

and

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

, inhabiting a variety of environments, from arid areas to rainforest. Most lay eggs in paired strings that hatch into

tadpole A tadpole or polliwog (also spelled pollywog) is the Larva, larval stage in the biological life cycle of an amphibian. Most tadpoles are fully Aquatic animal, aquatic, though some species of amphibians have tadpoles that are terrestrial animal, ...

s, although, in the genus '' Nectophrynoides'', the eggs hatch directly into miniature toads. All true toads are toothless and generally warty in appearance. They have a pair of

parotoid gland The parotoid gland (alternatively, paratoid gland) is an external skin gland on the back, neck, and shoulder of some frogs (especially toads), and salamanders. It can secrete a number of milky alkaloid substances (depending on the species) known ...

s on the back of their heads. These glands contain an

alkaloid Alkaloids are a broad class of natural product, naturally occurring organic compounds that contain at least one nitrogen atom. Some synthetic compounds of similar structure may also be termed alkaloids. Alkaloids are produced by a large varie ...

poison which the toads excrete when stressed. The poison in the glands contains a number of toxins causing different effects.

Bufotoxin Bufotoxins are a family of toxic steroid lactones or substituted Substituted tryptamine, tryptamines of which some are toxic. They occur in the parotoid glands, skin, and poison of many toads (True toad, Bufonidae family) and other amphibians, an ...

is a general term. Different animals contain significantly different substances and proportions of substances. Some, like the

cane toad The cane toad (''Rhinella marina''), also known as the giant neotropical toad or marine toad, is a large, Terrestrial animal, terrestrial true toad native to South America, South and mainland Central America, but which has been Introduced spe ...

''Rhinella marina'', are more toxic than others. Some " psychoactive toads", such as the Colorado River toad ''Incilius alvarius'', have been used recreationally for the effects of their bufotoxin. Depending on the species, male or female toads may possess a Bidder's organ, a trait unique to all bufonids except genera ''Melanophryniscus'' and ''Truebella''. Under the right conditions, the organ becomes an active ovary. The loss of teeth has arisen in frogs independently over 20 times. Notably, all members of Bufonidae are toothless. Another Anuran family with a comparable degree of edentulism is the family Microhylidae.Paluh, Daniel J., et al. “Rampant Tooth Loss Across 200 Million Years of Frog Evolution.” BioRxiv, 2021. Crossref, doi:10.1101/2021.02.04.429809.

Reproduction

Internal fertilization Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For inte ...

occurs in four bufonid genera. *'' Mertensophryne'' (some species) *'' Nectophrynoides'' (presumably all species) *'' Altiphrynoides malcolmi'' (one out of two species in the genus '' Altiphrynoides'') *'' Nimbaphrynoides occidentalis'' (the sole species in the monotypic genus '' Nimbaphrynoides'') '' Ascaphus'' (all species) and '' Eleutherodactylus'' (two species, '' E. coqui'' and '' E. jasperi'') are the only other frog genera that have internal fertilization. '' Limnonectes larvaepartus'' also has internal fertilization.

Taxonomy and genera

The family Bufonidae contains over 570 species among 52 genera. The family also contains an ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'' species, "''Bufo''" ''scorteccii'' .

References

* * Stebbins, Robert. ''Western Reptiles & Amphibians'' (3rd ed.). Houghton Mifflin Co., 2003. * Halliday, Tim R., and Kraig Adler (editors). ''The New Encyclopedia of Reptiles & Amphibians''. Facts on File, New York, 2002.

External links

Tolweb.org: BufonidaeBufonidae.com

Amphibian and Reptiles of Peninsular Malaysia - Family BufonidaeBufonidae recordings
from the British Library Sound Archive {{Authority control * Extant Thanetian first appearances Amphibian families Taxa named by John Edward Gray