Lungfish
Encyclopedia
Lungfish are freshwater fish belonging to the Subclass Dipnoi. Lungfish are best known for retaining characteristics primitive within the Osteichthyes
, including the ability to breathe air, and structures primitive within Sarcopterygii
, including the presence of lobed fins with a well-developed internal skeleton. Today, they live only in Africa
, South America
and Australia
. While vicariance
would suggest this represents an ancient distribution limited to the Mesozoic
supercontinent
Gondwana
, the fossil
record suggests that advanced lungfish had a widespread freshwater distribution and that the current distribution of modern lungfish species reflects extinction
of many lineages following the breakup of Pangaea
, Gondwana
and Laurasia
.
and an extensively developed palatal dentition. The lungfish is omnivorous
, feeding on fish, insects, crustaceans, worms, molluscs, amphibians and plant matter. They have a spiral valve
rather than a true stomach
. Basal lungfish groups may retain marginal teeth and an ossified braincase, but derived lungfish groups, including all modern species, show a significant reduction in the marginal bones and a cartilaginous braincase. The bones of the skull roof
in primitive lungfish are covered in a mineralized tissue
called cosmine, but in post-Devonian
lungfishes, the skull roof lies beneath the skin and the cosmine covering is lost. All modern lungfish show significant reductions and fusions of the bones of the skull roof, and the specific bones of the skull roof show no homology
to the skull roof bones of ray-finned fishes or tetrapods. During the breeding season, the South American lungfish develops a pair of feathery appendages that are actually highly modified pelvic fins. It is thought these fins improve gas exchange around the fish's eggs in its nest.
Through convergent evolution
, lungfishes have evolved internal nostrils similar to the tetrapods' choana
.
The dentition of lungfish is different from that of any other vertebrate
group. "Odontode
s" on the palate and lower jaws develop in a series of rows to form a fan-shaped occlusion
surface. These odontodes then wear to form a uniform crushing surface. In several groups, including the modern lepidosireniformes
, these ridges have been modified to form occluding blades.
The modern lungfishes have a number of larval features, which suggest paedomorphosis. They also demonstrate the largest genome
among the vertebrates.
Modern lungfish all have an elongate body with fleshy paired pectoral and pelvic fins and a single unpaired caudal fin replacing the dorsal, caudal and anal fin of most fishes.
. The lungs of lungfish are homologous
to the lungs of tetrapod
s. As in tetrapods and bichir
s, the lungs extend from the ventral surface of the esophagus
and gut.
While other species of fish can breathe air via modified, vascularized gas bladder
s, these bladders are usually simple sacs, devoid of complex internal structure. In contrast, the lungs of lungfish are subdivided into numerous smaller air sacs, maximising the surface area available for gas exchange.
. When a lungfish is obtaining oxygen
from its gills, its circulatory system is configured similarly to the common fish. The spiral valve of the conus arteriosus is open, the by-pass arterioles of the 3rd and 4th gill arches (which do not actually have gills) are shut, the 2nd, 5th and 6th gill arch arterioles are open, the ductus arteriosus branching off the 6th arteriole is open and the pulmonary arteries are closed. As the water passes through the gills, the lungfish uses a buccal pump. Flow though the mouth and gills is unidirectional. Blood flow through the secondary lamellae is countercurrent to the water, maintaining a more constant concentration gradient.
throughout the dry season. Changes in physiology
allow the lungfish to slow its metabolism
to as little as 1/60th of the normal metabolic rate, and protein waste is converted from ammonia
to less-toxic urea
(normally, lungfish excrete nitrogenous waste as ammonia directly into the water).
Burrowing is seen in at least one group of fossil lungfish, the Gnathorhizidae
. It has been proposed both that burrowing is plesiomorphic for lungfish as well as that gnathorhizids are directly ancestral to modern Lepidosireniformes, but it is possible that the similarity is simply due to convergent
or parallel evolution
.
Lungfish can be extremely long-lived. The Queensland lungfish
at the Shedd Aquarium
in Chicago
has been part of the permanent live collection since 1933.http://www.sheddaquarium.org/granddad.html
is well-understood:
The relationships among lungfishes are significantly more difficult to resolve. While Devonian lungfish had enough bone in the skull to determine relationships, post-Devonian lungfish are represented entirely by skull roofs and teeth, as the rest of the skull is cartilaginous
. Additionally, many of the taxa that have been identified may not be monophyletic. Current phylogenetic studies support the following relationships of major lungfish taxa:
Class Osteichthyes
Subclass Sarcopterygii
Order Dipnoi
,--Family Diabolichthyidae (extinct)
| ,--Family Uranolophidae
(extinct)
| | __,--Family Speonesydrionidae (extinct)
'-|-| '--Family Dipnorhynchidae
(extinct)
| ,--Family Stomiahykidae
(extinct)
'----|___ ,--Family Chirodipteridae
(extinct)
| '-|--Family Holodontidae (extinct)
|------Family Dipteridae
(extinct)
| __,--Family Fleurantiidae (extinct)
'-| '--Family Rhynchodipteridae
(extinct)
'--Family Phaneropleuridae (extinct)
| ,--Family Ctenodontidae (extinct)
'-| ,--Family Sagenodontidae (extinct)
'-|--Family Gnathorhizidae
(extinct)
'--Order Ceratodontiformes
|--family Asiatoceratodontidae (extinct)
|--Family Ptychoceratodontidae (extinct)
|--Family Ceratodontidae
| '--Genus Ceratodus
(extinct)
| '--Genus Metaceratodus
(extinct)
'--Family Neoceratodontidae
| '--Genus Mioceratodus
(extinct)
| '--Genus Neoceratodus - Queensland lungfish
'--Order Lepidosireniformes
'--Family Lepidosirenidae - South American lungfish
'--Family Protopteridae - African lungfish
Osteichthyes
Osteichthyes , also called bony fish, are a taxonomic group of fish that have bony, as opposed to cartilaginous, skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of over 29,000 species...
, including the ability to breathe air, and structures primitive within Sarcopterygii
Sarcopterygii
The Sarcopterygii or lobe-finned fishes – sometimes considered synonymous with Crossopterygii constitute a clade of the bony fishes, though a strict classification would include the terrestrial vertebrates...
, including the presence of lobed fins with a well-developed internal skeleton. Today, they live only in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. While vicariance
Vicariance
Vicariance is a process by which the geographical range of an individual taxon, or a whole biota, is split into discontinuous parts by the formation of a physical barrier to gene flow or dispersal. Vicariance of whole biotas occurs following large-scale geophysical events such as the uplift of a...
would suggest this represents an ancient distribution limited to the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
, the fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
record suggests that advanced lungfish had a widespread freshwater distribution and that the current distribution of modern lungfish species reflects extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
of many lineages following the breakup of Pangaea
Pangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
, Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
and Laurasia
Laurasia
In paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...
.
Anatomy and morphology
All lungfish demonstrate an uninterrupted cartilaginous notochordNotochord
The notochord is a flexible, rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes...
and an extensively developed palatal dentition. The lungfish is omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
, feeding on fish, insects, crustaceans, worms, molluscs, amphibians and plant matter. They have a spiral valve
Spiral valve
A spiral valve is the lower portion of the intestine of some sharks, rays, skates and bichirs. A modification of the ileum, the spiral valve is internally twisted or coiled to increase the surface area of the intestine, to increase nutrient absorption....
rather than a true stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
. Basal lungfish groups may retain marginal teeth and an ossified braincase, but derived lungfish groups, including all modern species, show a significant reduction in the marginal bones and a cartilaginous braincase. The bones of the skull roof
Skull roof
The skull roof , or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes and all land living vertebrates. The bones are derived from dermal bone, hence the alternative name dermatocranium...
in primitive lungfish are covered in a mineralized tissue
Mineralized tissues
Mineralized tissues are biological tissues that incorporate minerals into soft matrices. Typically these tissues form a protective shield or structural support...
called cosmine, but in post-Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
lungfishes, the skull roof lies beneath the skin and the cosmine covering is lost. All modern lungfish show significant reductions and fusions of the bones of the skull roof, and the specific bones of the skull roof show no homology
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
to the skull roof bones of ray-finned fishes or tetrapods. During the breeding season, the South American lungfish develops a pair of feathery appendages that are actually highly modified pelvic fins. It is thought these fins improve gas exchange around the fish's eggs in its nest.
Through convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
, lungfishes have evolved internal nostrils similar to the tetrapods' choana
Choana
Choana is the posterior nasal aperture.The choanae are separated by the vomer.- Boundaries :It is the opening between the nasal cavity and the nasopharynx....
.
The dentition of lungfish is different from that of any other vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
group. "Odontode
Odontode
Odontodes, or dermal teeth, are hard structures found on the external surfaces of animals or near internal openings. They comprise a soft pulp surrounded by dentine and covered by a mineralized substance such as enamel, a structure similar to that of teeth. They generally do not have the same...
s" on the palate and lower jaws develop in a series of rows to form a fan-shaped occlusion
Occlusion (dentistry)
Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary and mandibular teeth when they approach each other, as occurs during chewing or at rest....
surface. These odontodes then wear to form a uniform crushing surface. In several groups, including the modern lepidosireniformes
Lepidosireniformes
Lepidosireniformes is the order of lungfish containing the families Lepidosirenidae and Protopteridae ....
, these ridges have been modified to form occluding blades.
The modern lungfishes have a number of larval features, which suggest paedomorphosis. They also demonstrate the largest genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
among the vertebrates.
Modern lungfish all have an elongate body with fleshy paired pectoral and pelvic fins and a single unpaired caudal fin replacing the dorsal, caudal and anal fin of most fishes.
Lungs
All lungfish have two lungs, with the exception of the Australian lungfish, which only has one. The lung(s) connect to the pharynxPharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
. The lungs of lungfish are homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
to the lungs of tetrapod
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
s. As in tetrapods and bichir
Bichir
The bichirs are a family, Polypteridae, of archaic-looking ray-finned fishes, the sole family in the order Polypteriformes.All species occur in freshwater habitats in tropical Africa and the Nile River system, mainly swampy, shallow floodplains and estuaries.-Anatomy and appearance:Bichirs are...
s, the lungs extend from the ventral surface of the esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
and gut.
While other species of fish can breathe air via modified, vascularized gas bladder
Gas bladder
The swim bladder, gas bladder, fish maw or air bladder is an internal gas-filled organ that contributes to the ability of a fish to control its buoyancy, and thus to stay at the current water depth without having to waste energy in swimming...
s, these bladders are usually simple sacs, devoid of complex internal structure. In contrast, the lungs of lungfish are subdivided into numerous smaller air sacs, maximising the surface area available for gas exchange.
Perfusion of water
Of extant lungfish, only the Australian lungfish can respire through its gills. In other species of lungfish, the gills are too atrophied to allow for adequate gas exchangeGas exchange
Gas exchange is a process in biology where gases contained in an organism and atmosphere transfer or exchange. In human gas-exchange, gases contained in the blood of human bodies exchange with gases contained in the atmosphere. Human gas-exchange occurs in the lungs...
. When a lungfish is obtaining oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
from its gills, its circulatory system is configured similarly to the common fish. The spiral valve of the conus arteriosus is open, the by-pass arterioles of the 3rd and 4th gill arches (which do not actually have gills) are shut, the 2nd, 5th and 6th gill arch arterioles are open, the ductus arteriosus branching off the 6th arteriole is open and the pulmonary arteries are closed. As the water passes through the gills, the lungfish uses a buccal pump. Flow though the mouth and gills is unidirectional. Blood flow through the secondary lamellae is countercurrent to the water, maintaining a more constant concentration gradient.
Perfusion of air
When breathing air, the spiral valve of the conus arteriosus closes (minimizing the mixing of oxygenated and deoxygenated blood), the 3rd and 4th gill arches open, the 2nd and 5th gill arches close (minimizing the possible loss of oxygen that was obtained in the lungs through the gills), the 6th arteriole's ductus arteriosus is closed, and the pulmonary arteries open. It is important to note that during air breathing, the 6th gill is still used in respiration; deoxygenated blood loses some of its carbon dioxide as it passes though the gill before reaching the lung. This is because carbon dioxide is more soluble in water. Air flow through the mouth is tidal, and through the lungs it is bidirectional and observes "uniform pool" diffusion of oxygen.Ecology and life history
African and South American lungfish are capable of surviving seasonal drying out of their habitats by burrowing into mud and estivatingEstivation
Aestivation is a state of animal dormancy, characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions...
throughout the dry season. Changes in physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
allow the lungfish to slow its metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
to as little as 1/60th of the normal metabolic rate, and protein waste is converted from ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
to less-toxic urea
Urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
(normally, lungfish excrete nitrogenous waste as ammonia directly into the water).
Burrowing is seen in at least one group of fossil lungfish, the Gnathorhizidae
Gnathorhizidae
The Gnanthorhizidae are an extinct family of lungfish that lived from the late Carboniferous until the middle Triassic. Gnathorhizid fossils have been found in North America, Madagascar, Australia, and possibly Eastern Europe and South Africa...
. It has been proposed both that burrowing is plesiomorphic for lungfish as well as that gnathorhizids are directly ancestral to modern Lepidosireniformes, but it is possible that the similarity is simply due to convergent
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
or parallel evolution
Parallel evolution
Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...
.
Lungfish can be extremely long-lived. The Queensland lungfish
Queensland Lungfish
The Queensland lungfish, Neoceratodus forsteri is the sole surviving member of the family Ceratodontidae and order Ceratodontiformes. It is one of only six extant lungfish species in the world...
at the Shedd Aquarium
Shedd Aquarium
The John G. Shedd Aquarium is an indoor public aquarium in Chicago, Illinois in the United States that opened on May 30, 1930. The aquarium contains over 25,000 fish, and was for some time the largest indoor aquarium in the world with of water. The Shedd Aquarium was the first inland aquarium with...
in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
has been part of the permanent live collection since 1933.http://www.sheddaquarium.org/granddad.html
Taxonomy
The relationship of lungfishes to the rest of the bony fishOsteichthyes
Osteichthyes , also called bony fish, are a taxonomic group of fish that have bony, as opposed to cartilaginous, skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of over 29,000 species...
is well-understood:
- Lungfishes are most closely related to Powichthyes, and then to the PorolepiformesPorolepiformesPorolepiformes is an order of prehistoric lobe-finned fish which lived during the Devonian period . The group contains two families: Holoptychiidae and Porolepididae....
. - Together, these taxa form the Dipnomorpha, the sister group to the TetrapodomorphaTetrapodomorphaTetrapodomorpha is a clade of vertebrates, consisting of tetrapods and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish...
. - Together, these form the RhipidistiaRhipidistiaThe Rhipidistia were lobe-finned fishes that are the ancestors of the tetrapods. Taxonomists traditionally considered the Rhipidistia a subgroup of Crossopterygii that described a group of fish that lived during the Devonian consisting of the Porolepiformes and Osteolepiformes...
, the sister group to the CoelacanthCoelacanthCoelacanths are members of an order of fish that includes the oldest living lineage of Sarcopterygii known to date....
s.
The relationships among lungfishes are significantly more difficult to resolve. While Devonian lungfish had enough bone in the skull to determine relationships, post-Devonian lungfish are represented entirely by skull roofs and teeth, as the rest of the skull is cartilaginous
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
. Additionally, many of the taxa that have been identified may not be monophyletic. Current phylogenetic studies support the following relationships of major lungfish taxa:
Class Osteichthyes
Subclass Sarcopterygii
Order Dipnoi
,--Family Diabolichthyidae (extinct)
| ,--Family Uranolophidae
Uranolophidae
Uranolophidae is an extinct family of prehistoric lungfishes which lived during the Devonian period. Fossils have been found in North America.-Phylogeny:* Sarcopterygii ** Dipnoi *** Uranolophina **** Uranolophidae...
(extinct)
| | __,--Family Speonesydrionidae (extinct)
'-|-| '--Family Dipnorhynchidae
Dipnorhynchidae
Dipnorhynchidae is an extinct family of prehistoric lungfishes which lived during the Devonian period.-Phylogeny:* Sarcopterygii ** Dipnoi *** Dipnorhynchidae **** Dipnorhynchus **** Ganorhynchus...
(extinct)
| ,--Family Stomiahykidae
Stomiahykidae
Stomiahykidae is an extinct family of prehistoric lungfishes which lived during the Devonian period.-Phylogeny:* Sarcopterygii ** Dipnoi *** Stomiahykidae **** †Archaeonectes **** †Stomiakykus...
(extinct)
'----|___ ,--Family Chirodipteridae
Chirodipteridae
Chirodipteridae is an extinct family of prehistoric lungfishes that lived during the Devonian period....
(extinct)
| '-|--Family Holodontidae (extinct)
|------Family Dipteridae
Dipteridae
Dipteridae is an extinct family of prehistoric lungfishes which lived during the Devonian period.-Phylogeny:* Sarcopterygii ** Dipnoi *** Dipteridae **** †Amadeodipterus **** †Conchodus...
(extinct)
| __,--Family Fleurantiidae (extinct)
'-| '--Family Rhynchodipteridae
Rhynchodipteridae
Rhynchodipteridae is a family of prehistoric lungfishes which lived during the Devonian period.-Phylogeny:* Sarcopterygii ** Dipnoi *** Rhynchodipteridae **** †Rhynchodipterus **** †Soederberghia...
(extinct)
'--Family Phaneropleuridae (extinct)
| ,--Family Ctenodontidae (extinct)
'-| ,--Family Sagenodontidae (extinct)
'-|--Family Gnathorhizidae
Gnathorhizidae
The Gnanthorhizidae are an extinct family of lungfish that lived from the late Carboniferous until the middle Triassic. Gnathorhizid fossils have been found in North America, Madagascar, Australia, and possibly Eastern Europe and South Africa...
(extinct)
'--Order Ceratodontiformes
|--family Asiatoceratodontidae (extinct)
|--Family Ptychoceratodontidae (extinct)
|--Family Ceratodontidae
| '--Genus Ceratodus
Ceratodus
Ceratodus was a wide-ranging genus of extinct sarcopterygiian lungfish. Fossil evidence dates back to the Middle Triassic 228 million years ago. A wide range of fossil species from different time periods have been found around the world in places such as the United States, Argentina, England,...
(extinct)
| '--Genus Metaceratodus
Metaceratodus
Metaceratodus is an extinct genus of prehistoric sarcopterygian or lobe-finned fish. From the Early Cretaceous of Queensland, Australia.-See also:* Sarcopterygii* List of sarcopterygians* List of prehistoric bony fish...
(extinct)
'--Family Neoceratodontidae
| '--Genus Mioceratodus
Mioceratodus
Mioceratodus is an extinct genus of prehistoric sarcopterygian or lobe-finned fish.-See also:* Sarcopterygii* List of sarcopterygians* List of prehistoric bony fish...
(extinct)
| '--Genus Neoceratodus - Queensland lungfish
Queensland Lungfish
The Queensland lungfish, Neoceratodus forsteri is the sole surviving member of the family Ceratodontidae and order Ceratodontiformes. It is one of only six extant lungfish species in the world...
'--Order Lepidosireniformes
'--Family Lepidosirenidae - South American lungfish
South American lungfish
The South American lungfish, Lepidosiren paradoxa, is the single species of lungfish found in swamps and slow-moving waters of the Amazon, Paraguay, and lower Paraná River basins in South America. Notable as an obligate air-breather, it is the sole member of its family Lepidosirenidae...
'--Family Protopteridae - African lungfish
See also
- Lepidogalaxias salamandroides
- South American lungfishSouth American lungfishThe South American lungfish, Lepidosiren paradoxa, is the single species of lungfish found in swamps and slow-moving waters of the Amazon, Paraguay, and lower Paraná River basins in South America. Notable as an obligate air-breather, it is the sole member of its family Lepidosirenidae...
- African lungfish
- Australian lungfish