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A true toad is any member of the
family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Bufonidae, in the order Anura (frogs and toads). This is the only family of anurans in which all members are known as
toad Toad 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. A distinction between frogs and toads is not made in scient ...
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 relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
. Some studies date the origin of the group to after the breakup of
Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...
, about 78 - 98 million years ago in the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', ...
. 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 ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
, 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 ''Ingerophrynus'' is a genus of true toads with 12 species. The genus is found in southern Yunnan and Southeast Asia; from Myanmar and Indochina to peninsular Thailand and Malaya, Sumatra, Borneo, Java, Nias Island, Sulawesi, and the Philippine ...
'' alongside '' Leptophryne'' was grouped as basal to the clade containing all other
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...
n toad genera and '' Ghatophryne'' by Portik and Papenfuss, but was found to group with '' Phrynoidis'' and ''
Rentapia ''Rentapia'' is a genus of true toads, family Bufonidae. It is endemic to Southeast Asia and occurs in the Malay Peninsula (including extreme southern peninsular Thailand), Borneo, and Sumatra. It was erected in 2016 resolve the polyphyly of ...
'' by Chan ''et al.'' ''Ghatophryne'' was grouped with ''Phrynoidis'' and ''Rentapia'' by Portik and Papenfuss but was found to group with ''
Pelophryne ''Pelophryne'', commonly known as flathead toads or dwarf toads, is a genus of true toads, family Bufonidae. The genus occurs in the Philippines, Borneo, Malay Peninsula, Malaya including Singapore, and Hainan (China). Molecular data suggest that ...
'' and '' Ansonia'' by Chan ''et al.'' In addition, ''
Sabahphrynus ''Sabahphrynus'' is a monotypic genus of amphibians in the family Bufonidae. The sole species is ''Sabahphrynus maculatus'', also known as the spotted Asian tree toad or Sabah earless toad. It is endemic to Borneo where it is only known from Sab ...
'' 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 sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
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, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
, inhabiting a variety of environments, from arid areas to rainforest. Most lay eggs in paired strings that hatch into
tadpole A tadpole is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found ...
s, although, in the genus ''
Nectophrynoides ''Nectophrynoides'' is a genus of true toads, family Bufonidae. They are endemic to Eastern Arc forests and wetlands in Tanzania,Channing and Howell. (2006). ''Amphibians of East Africa.'' Pp. 104–117. and all except '' N. tornieri'' are thr ...
'', the eggs hatch directly into miniature toads. All 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 Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of simila ...
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 ''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 ''Nectophrynoides'' is a genus of true toads, family Bufonidae. They are endemic to Eastern Arc forests and wetlands in Tanzania,Channing and Howell. (2006). ''Amphibians of East Africa.'' Pp. 104–117. and all except '' N. tornieri'' are thr ...
'' (presumably all species) *'' Altiphrynoides malcolmi'' (one out of two species in the genus '' Altiphrynoides'') *'' Nimbaphrynoides occidentalis'' (the sole species in the monotypic genus ''
Nimbaphrynoides ''Nimbaphrynoides'' is a monotypic genus of true toads from highlands in the Mount Nimba region of the West African countries of Guinea, Liberia, and Côte d'Ivoire. The sole species is ''Nimbaphrynoides occidentalis''. Along with ''Nectophryno ...
'') '' Ascaphus'' (all species) and '' Eleutherodactylus'' (two species, '' E. coqui'' and '' E. jasperi'') are the only other frog genera that have internal fertilization. ''
Limnonectes larvaepartus ''Limnonectes larvaepartus'' is a species of fanged frog in the family Dicroglossidae endemic to northern and western Sulawesi, Indonesia. It is unique in that it has internal fertilization and gives live birth to tadpoles. Other frog species t ...
'' also has internal fertilization.


Taxonomy and genera

The family Bufonidae contains over 570 species among 52 genera.


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.comAmphibian and Reptiles of Peninsular Malaysia - Family BufonidaeBufonidae recordings
from the
British Library Sound Archive The British Library Sound Archive, formerly the British Institute of Recorded Sound; also known as the National Sound Archive (NSA), in London, England is among the largest collections of recorded sound in the world, including music, spoken word a ...
{{Authority control * Extant Thanetian first appearances Amphibian families Taxa named by John Edward Gray