Overview

Brief Summary

Introduction

Anura is the clade of living frogs and their close fossil relatives. The name Anura refers to the lack of a tail.

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Frog Reproductive Cycle

Most people learn about the basics of frog reproduction in elementary school. Frogs lay eggs in water, and the eggs hatch into tadpoles that grow into frogs. Only about half of all frogs follow these exact steps, but there are a few rules of thumb about frog reproduction. All frogs reproduce sexually, and all hatch from eggs.

In almost all frogs, egg fertilization happens outside the female's body instead of inside. The female releases her eggs and the male releases his sperm at the same time. In order to make sure that the sperm reach the eggs, the male and female get into a mating posture called amplexus. The male climbs onto the female's back and clasps his forelegs around her middle. Frogs can stay in amplexus for hours or even days as the female releases as few as one or as many as several hundred eggs.

Sometimes, it's easy to tell male frogs from female frogs. Many species are sexually dimorphic, meaning that there are differences between the bodies and colors of males and females. But in some species, males and females are hard to tell apart. In such species, male frogs often produce a release call when clasped by another male. During mating season, researchers can use release calls to tell which frogs are male and which are female.

All frogs' eggs require moisture to develop, and most frogs abandon their eggs once they're fertilized. But not all eggs incubate underwater or without parental care. A few species carry their eggs in their vocal sacs or their abdomens. Others lay eggs in dry areas and keep the eggs moist with water or urine. Depending on the frog's species and the climate in which it typically lives, the eggs can hatch in a few days to a few weeks.

In a few species, fully formed froglets hatch from the eggs, but most of the time the frog starts its life as a tadpole. While adult frogs are carnivores, tadpoles can be vegetarians or omnivores. Some are filter feeders that eat algae, and others have teeth and can eat anything from rotting vegetation to other tadpoles. Either way, tadpoles tend to be voracious eaters -- it takes a lot of energy to complete their metamorphosis into frogs.

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Comprehensive Description

Characteristics

When only living taxa are considered, a list of synapomorphies of Anura would include many of the obvious distinctive features of frogs:

  • Shortened vertebral column (nine or fewer presacral vertebrae)
  • Presence of a urostyle formed from developing tail vertebrae
  • Absence of tail in adults
  • Hindlimb longer than forelimb
  • Fusion of radius and ulna into a single element
  • Fusion of tibia and fibula into a single element
  • Elongate ankle bones (tibiale and fibulare = astragalus and calcaneum)
  • Absence of a prefrontal bone
  • Fusion of separate hyobranchial elements into a hyobranchial (=hyoid) plate
  • A tongue that lacks intrinsic skeletal support from the hyobranchial plate
  • A tadpole, with keratinous beaks and denticles as larval mouthparts
  • A single median spiracle in the larva (characteristic of Orton's Type 3 tadpole)
  • Large subcutaneous lymph spaces between the skin and muscle layer
  • Two protractor lentis muscles attached to lens

(Milner, 1988, 1993; Saint-Aubain, 1981; Trueb and Cloutier, 1991).

However, the existence of several early frog fossils, such as †Prosalirus and †Notobatrachus, clouds this picture, because many of these characters cannot be assessed in these fossils, either because of incompleteness of fossils or because the features are soft-tissue characters identifiable only in living taxa.

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Distribution

Range Description

This taxon is known only from the non-specific type locality of "Cordofan", which is in modern-day Sudan, and not in Egypt (Baha El Din pers. comm.).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This is presumably an aquatic species that breeds by larval development.

Systems
  • Freshwater
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Associations

Animal / pathogen
Batrachochytrium dendrobatidis infects Anura

Animal / rests in
encapsulated cystacanth of Centrorhynchus aluconis rests inside mesentery of Anura

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Known predators

Anura is prey of:
Thamnophis
Crocodylus niloticus
Falconiformes
Testudines
Serpentes
Gavialis gangeticus
Salvelinus fontinalis

Based on studies in:
Canada: Manitoba (Grassland)
Malawi (River)
Africa, Crocodile Creek, Lake Nyasa (Lake or pond)
Russia (Agricultural)
Malaysia (Swamp)
Canada: Ontario (River)

This list may not be complete but is based on published studies.
  • G. Fryer, The trophic interrelationships and ecology of some littoral communities of Lake Nyasa, Proc. London Zool. Soc. 132:153-229, from p. 219 (1959).
  • N. N. Smirnov, Food cycles in sphagnous bogs, Hydrobiologia 17:175-182, from p. 179 (1961).
  • T. Mizuno and J. I. Furtado, Food chain. In: Tasek Bera, J. I. Furtado and S. Mori, Eds. (Junk, The Hague, Netherlands, 1982), pp. 357-359, from p. 358.
  • G. Fryer, 1957. The trophic interrelationships and ecology of some littoral communities of Lake Nyasa with special reference to the fishes, and a discussion of the evolution of a group of rock-frequenting Cichlidae. Proc. Zool. Soc. London 132:153-281, f
  • W. E. Ricker, 1934. An ecological classification of certain Ontario streams. Univ. Toronto Studies, Biol. Serv. 37, Publ. Ontario Fish. Res. Lab. 49:7-114, from pp. 105-106.
  • R. D. Bird, Biotic communities of the Aspen Parkland of central Canada, Ecology, 11:356-442, from p. 383 (1930).
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Known prey organisms

Anura preys on:
Insecta
Hemiptera
Diptera
Araneae
Gastropoda
algae
detritus
angiosperms
Lepidoptera
Orchelimum vulgare
Pseudacris triseriata
Plethodon cinereus
Storeria dekayi
Gallinula chloropus
Amazilia tzacatl
Mellisuga helenae

Based on studies in:
Canada: Manitoba (Grassland)
Malawi (River)
Malaysia (Swamp)
Africa, Crocodile Creek, Lake Nyasa (Lake or pond)
Russia (Agricultural)

This list may not be complete but is based on published studies.
  • G. Fryer, The trophic interrelationships and ecology of some littoral communities of Lake Nyasa, Proc. London Zool. Soc. 132:153-229, from p. 219 (1959).
  • N. N. Smirnov, Food cycles in sphagnous bogs, Hydrobiologia 17:175-182, from p. 179 (1961).
  • T. Mizuno and J. I. Furtado, Food chain. In: Tasek Bera, J. I. Furtado and S. Mori, Eds. (Junk, The Hague, Netherlands, 1982), pp. 357-359, from p. 358.
  • G. Fryer, 1957. The trophic interrelationships and ecology of some littoral communities of Lake Nyasa with special reference to the fishes, and a discussion of the evolution of a group of rock-frequenting Cichlidae. Proc. Zool. Soc. London 132:153-281, f
  • R. D. Bird, Biotic communities of the Aspen Parkland of central Canada, Ecology, 11:356-442, from p. 406 (1930).
  • R. D. Bird, Biotic communities of the Aspen Parkland of central Canada, Ecology, 11:356-442, from p. 383 (1930).
  • Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org
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Evolution and Systematics

Evolution

Discussion of Phylogenetic Relationships

View Anura Tree

The node-based name Anura was defined by Ford and Cannatella (1993) as the last common ancestor of living frogs and all its descendants. According to this definition, †Triadobatrachus is not part of Anura, following Trueb and Cloutier (1991). The late Jurassic fossil †Notobatrachus degiustoi has been considered as having uncertain placement with respect to Anura--possibly the sister-group, possibly not (Cannatella, 1985); or related to Leiopelma (Estes and Reig, 1973). Baez and Basso (1996) placed it as the sister-group of Anura.

Vieraella herbstii is another relatively complete early Jurassic fossil, but is less well-preserved than †Notobatrachus (Estes and Reig, 1973). The presence of nine presacral vertebrae places it among the basal salientians, but other characters are not sufficiently preserved to permit definitive placement in Anura. A third well-preserved Jurassic fossil taxon, †Eodiscoglossus santonje, has eight presacral vertebrae (Estes and Reig, 1973), and thus is clearly within Anura. †Prosalirus bitis is from the Early Jurassic (Pliensbachian) of Arizona; the putative limbed caecilian †Eocaecilia is from the same formation. It is reputed to be the earliest known "frog" in the sense that it has froglike features such as a urostyle and elongate, anteriorly directed ilia. For more details see the leaf page on †Prosalirus.
The monophyly of Anura has rarely been questioned. Griffiths (1963:279) considered Anura to be diphyletic; i.e., Ascaphus and Leiopelma comprised one lineage, and all other frogs a second, "...stemming independently from either different levels of a single proanuran organization or different proanuran stocks." Rocek (1981) considered †Triadobatrachus to be within Anura, and placed Pelobatidae (including only Pelobates and some related fossils), and somewhat tentatively, Pipidae, †Palaeobatrachidae, and Rhinophrynidae, in Archaeosalientia. †Triadobatrachus and remaining anurans were included in Neosalientia. The character distinguishing the two groups is a median dermal bone, the interparietal (Reinbach, 1939), which Rocek homologized with the median extrascapular of the osteolepiform fish †Eusthenopteron. The interparietal is found in Pelobates and some fossil relatives, but not in any pipoid frogs. Milner (1988) provided a cogent review of the interpretation of this dermal element.

In a study of tetrapod phylogeny, Hedges et al. (1990) analyzed 123 phylogenetically informative sites from 18S ribosomal RNA of 21 tetrapods, including 4 salamanders, 4 caecilians, and 1 species each from Bufonidae, Discoglossidae, Hylidae, Leptodactylidae, Microhylidae, Pelobatidae, and Sooglossidae. Bootstrap analyses using both maximum-parsimony and neighbor-joining algorithms did not support the monophyly of Anura, Caudata, or Gymnophiona, but a monophyletic Amphibia was supported with a bootstrap value of 100%. Hedges and Maxson (1993) and Hillis et al. (1993) presented analyses of anuran relationships based on DNA sequence data from the mitochondrial and nuclear ribosomal genes, respectively.

Hedges et al. (1990) also analyzed 35 variable sites from 28S rRNA of four species of frogs, from Discoglossidae, Hylidae, Pelobatidae, and Pipidae. Bootstrap analysis of maximum parsimony trees yielded a monophyletic Anura, but with no resolution among the four taxa. The neighbor-joining analysis indicated a sister-group relationship between the discoglossid and pipid, and between the bufonid and hylid, but the bootstrap value for both of these nodes was less than 50%. Neither analysis yielded a monophyletic Amphibia.

Hay et al. (1995) is the most comprehensive molecular systematics treatment of the relationships among the families of amphibians. Their neighbor-joining tree yielded a monophlyletic Anura, Caudata, and Gymnophiona.

"Archaeobatrachia"

Archaeobatrachians have generally included discoglossoids, pipoids and pelobatoids (Duellman, 1975; Reig, 1958). As discussed on other pages, the synapomorphies of Bombinanura and Pipanura collectively demonstrate that "Archaeobatrachia" is paraphyletic. The informal term archaeobatrachian is a convenient term for anurans that are not part of Neobatrachia.

Bombinanura

Bombinanura, a node-based name, was defined by Ford and Cannatella (1993) to be the most recent common ancestor of living Bombinatoridae and Discoglossanura, and all its descendants. Synapomorphies of Bombinanura include fusion of the halves of the sphenethmoid, eight presacral vertebrae, absence of the m. epipubicus, and absence of the caudalipuboischiotibialis muscle (Cannatella, 1985). Subclades of Bombinanura include Bombinatoridae and Discoglossanura.

Discoglossidae and Discoglossoidea

Most analyses of molecular sequence data have placed Alytes, Discoglossus, Bombina, and Barbourula in a clade, to which the name Discoglossidae has been applied. In contrast, Ford and Cannatella (1993) listed derived morphological features that would require paraphyly of this group , and they recognized both Discoglossidae (for Alytes and Discoglossus) and Bombinatoridae (for Bombina and Barbourula). A synthesis of the two datasets has not been attempted. There are apparently no published synapomorphies for "Discoglossidae," and the dissimilarity of Alytes and Discoglossus, on one hand, and Bombina on the other, has often been noted (e.g., Lanza et al., 1976), suggesting a deep divergence between the two lineages. Griffiths (1963) stated that the diagnostic feature of Discoglossidae (sensu lato) was a triradiate sternum. However, this feature is also present in Leiopelma. The similarity can be interpreted either as shared plesiomorphy between Leiopelma and Discoglossidae, or a derived feature that unites Leiopelma more closely to Discoglossidae than to Ascaphus.

Pipanura

The node-based name Pipanura was proposed by Ford and Cannatella (1993) for the most recent common ancestor of living Mesobatrachia + Neobatrachia, and all its descendants. The subordinal name Ranoidei was coined for this clade by Sokol (1977), but that name was re-assigned to a less inclusive taxon by Dubois (1983, 1984). Sokol's (1977) use of this name was unfortunate because the informal name, ranoid, is homonymous with the widely used name Ranoidea.

Synapomorphies include a sinistral spiracle in the larvae (a characteristic feature of Orton's Type 4 tadpole), absence of free ribs in adults, torsion in the carpal elements, the presence of vocal sacs, and fusion of the trigeminal and facial ganglia (Cannatella, 1985; Sokol, 1975).

Acosmanura


Pelobatoidea

The name was applied to the node that is the common ancestor of living Megophryidae, Pelobatidae, and Pelodytes. Synapomorphies of Pelobatoidea include the presence of a palatine process of the maxilla and ossification of the sternum into a bony style (Cannatella, 1985). Duellman and Trueb (1986) listed the presence of a dorsal gap in the cricoid ring as a synapomorphy for this clade. However, there is no gap in Scaphiopus, Spea, Pelobates (except for the smallest species, P. fuscus), or several megophryids; at best, the presence of a dorsal gap would be an ambiguous synapomorphy. Relationships among the living pelobatoids are an unresolved trichotomy of Megophryidae, Pelobatidae, and Pelodytes.

Pipoidea

Pipoidea was defined by Cannatella and Ford (1993) to be the most recent common ancestor of living Pipidae + Rhinophrynidae, and all its descendants. Pipoidea is diagnosed by several distinctive synapomorphies, including the absence of mentomeckelian bones (see comments below on †Palaeobatrachidae), absence of lateral alae of the parasphenoid, fusion of the frontoparietals into an azygous element, greatly enlarged otic capsules, and a tadpole with paired spiracles, and lacking beaks and denticles (Orton Type 1 tadpole). Clades of Pipoidea include Pipidae, †Palaeobatrachidae, some unplaced fossil "pipids," and Rhinophrynidae.

Pipimorpha

The new stem-based name Pipimorpha was defined by Ford and Cannatella (1993) to be those taxa that are more closely related to living Pipidae than to living Rhinophrynus. Pending a more detailed assessment of the relationships of †Palaeobatrachidae, Pipidae, and the fossil "pipids," we consider †Palaeobatrachidae, †Thoraciliacus, †Cordicephalus, †Saltenia, †Shomronella, and †Eoxenopoides to be part of Pipimorpha.

"Mesobatrachia"

Ford and Cannatella (1993) applied the name Mesobatrachia to the node that is the most recent common ancestor of the living Pelobatoidea and Pipoidea. This relationship was based on synapomorphies discussed by Cannatella (1985). Mesobatrachia as proposed by Laurent (1979) was a paraphyletic group. Cannatella (1985) first applied the name to a clade. Synapomorphies reported for Mesobatrachia included closure of the frontoparietal fontanelle by juxtaposition of the frontoparietal bones, partial closure of the hyoglossal sinus by the ceratohyals, absence of the taenia tecti medialis, and absence of the taenia tecti transversum (Cannatella, 1985; Sokol, 1981).Most other previous taxonomies, and recent molecular phylogenetic analyses, have placed the Pelobatoidea as the sister-group to Neobatrachia, rather than to Pipoidea. Thus, the Mesobatrachia as formerly proposed is not monophyletic, and therefore no longer recognized.

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Functional Adaptations

Functional adaptation

Waterproof lipid-layer prevents desiccation: frogs
 

The skin of terrestrial frogs protects from water loss via a waterproof, lipid-containing layer.

   
  "Some species in the dry forests of South America secrete a waxy coating to protect themselves from drying out." (Morell 2001)

"The lipid contents of these organelles appear to consist of stacks of flattened lipid vesicles (Landmann, 1986, 1988) comprising primarily glycosphingolipids, free sterols and phospholipids, which are precursors of the stratum corneum lipids (Fig. 4). Eventually, the lipid contents of the organelles are secreted into the extracellular domain, where they are further processed into compact lipid bilayers that occlude the extracellular spaces among adjacent and overlapping corneocytes (Fig. 4), a condition that has been likened to a 'bricks-and-mortar' organization (Elias, 1983; Elias and Menon, 1991). It has been proposed that acylglucosylceramides serve as molecular 'rivets' to promote flattening and stacking of lipid vesicles that subsequently fuse edge-to-edge to produce lamellae comprising paired bilayers that are stacked parallel to the skin surface (Engström et al., 2000; Wertz, 2000). These form multiple lamellar sheets with smooth surfaces shown in freeze-fracture studies. In this manner, the extracellular lipids form a continuous domain throughout the stratum corneum and function as the principal barrier to water diffusion (Elias and Friend, 1975; Fig. 2)." (Lillywhite 2006:217)
  Learn more about this functional adaptation.
  • Virginia Morell. 2001. The fragile world of frogs. National Geographic. 199(5): 106-23.
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Functional adaptation

Three-chambered heart reduces mixing of blood: frog
 

The three-chambered heart of frogs reduces mixing of oxygenated and unoxygenated blood because of the separation of atrial inflow and outflow.

   
  "Although anurans have a three-chambered heart, little mixing of oxygenated and unoxygenated blood occurs because of the separation of atrial inflow and outflow." (Fowler and Miller 2003:22)
  Learn more about this functional adaptation.
  • Fowler, ME; Miller, RE. 2003. Zoo and Wild Animal Medicine. Philadelphia: W.B. Saunders Co.
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Functional adaptation

Concentrated form reduces water requirements: frogs
 

The jelly mass that holds the eggs of many frogs reduces internal water requirements because it is secreted in a concentrated form, which then takes up water from the external environment.

     
  "As far as I know, all extracellular mucuses and gels are secreted in concentrated form and then take up water--a conspicuous example is the jelly mass in which the eggs of a frog are suspended. When swollen, the mass is typically larger than the volume of the gravid female. Slime production by hagfish, according to John Gosline, provides an even more spectacular case." (Vogel 2003:444)
  Learn more about this functional adaptation.
  • Steven Vogel. 2003. Comparative Biomechanics: Life's Physical World. Princeton: Princeton University Press. 580 p.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records: 28256
Specimens with Sequences: 32443
Specimens with Barcodes: 20890
Species: 2303
Species With Barcodes: 2131
Public Records: 9207
Public Species: 645
Public BINs: 1762
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Barcode data

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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
DD
Data Deficient

Red List Criteria

Version
3.1

Year Assessed
2004

Assessor/s
Sherif Baha El Din

Reviewer/s
Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson and Neil Cox)

Contributor/s

Justification
Listed as Data Deficient in view of continuing doubts as to its taxonomic validity, extent of occurrence, status and ecological requirements.
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IUCN Red List of Threatened Species: data deficient

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IUCN Red List of Threatened Species: data deficient

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Population

Population
Its population is not known.

Population Trend
Unknown
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Threats

Major Threats
The threats to this species are not known.
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Management

Conservation Actions

Conservation Actions
It is not known if the species occurs in protected areas.
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Wikipedia

Rana cordofana

Rana cordofana is a species of frog in the Ranidae family. It is endemic to Sudan.

Its natural habitats are freshwater marshes and intermittent freshwater marshes.

Sources[edit]


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