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. Ideal ...

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 ''Bufo'' is a genus of true toads in the amphibian family Bufonidae. As traditionally defined, it was a wastebasket genus containing a large number of toads from much of the world, but following taxonomic reviews most of these have been moved ...

'' being the best known.

History

Bufonidae is thought to have originated in South America. 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 The Jurassic ( ) is a geologic period and st ...

, 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'', t ...

. 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'', "da ...

, 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, 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'' 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 ''

'' 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 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 Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

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 i ...

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 threa ...

'', 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 toads and some frogs and salamanders. It can secrete a number of milky alkaloid substances (depending on the species) known collective ...

s 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 similar st ...

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 tryptamines of which some may or may not be toxic. They occur in the parotoid glands, skin, and poison of many toads (genus ''Bufo'') and other amphibians, and in some plants and mus ...

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 true toad native to South and mainland Central America, but which has been introduced to various islands throughout Oceania ...

''Rhinella marina'', are more toxic than others. Some " psychoactive toads", such as the

Colorado River toad The Colorado River toad (''Incilius alvarius''), formerly known as the Sonoran Desert toad, is found in northern Mexico and the southwestern United States. It exudes toxins from glands within its skin that have psychoactive properties. Descript ...

''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 ''Mertensophryne'' is a genus of true toads (family Bufonidae). They are found in eastern and southern Democratic Republic of Congo to Kenya, Tanzania, Malawi, southeastern Zimbabwe, and adjacent Mozambique. Their common names include snouted fr ...

'' (some species) *''

'' (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 The tailed frogs are two species of frogs in the genus ''Ascaphus'', the only taxon in the family Ascaphidae . The "tail" in the name is actually an extension of the male cloaca. The tail is one of two distinctive anatomical features adapting the ...

'' (all species) and ''

Eleutherodactylus ''Eleutherodactylus'' is a genus of frogs in the family Eleutherodactylidae.Hedges, S. B., W. E. Duellman, and M. P. Heinicke . 2008. New World direct-developing frogs (Anura: Terrarana): molecular phylogeny, classification, biogeography, and co ...

'' (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.

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 ...

{{Authority control * Extant Thanetian first appearances Amphibian families Taxa named by John Edward Gray