The Gnathorhizidae are an extinct family of

lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...

that lived from the late Carboniferous until the middle

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

. Gnathorhizid

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s have been found in North America,

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

, Australia, and possibly

Eastern Europe Eastern Europe is a subregion of the European continent. As a largely ambiguous term, it has a wide range of geopolitical, geographical, ethnic, cultural, and socio-economic connotations. The vast majority of the region is covered by Russia, whic ...

and

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

. They are characterized by high-ridged toothplates that form cutting blades and a reduction in cranial bones.

Taxonomy

Phylogenetic evidence supports Gnathorhizidae being the sister group to the extant family

Lepidosirenidae Lepidosirenidae is a family of lungfish containing the genera ''Lepidosiren'' (the South American lungfish) and '' Protopterus'' (the African lungfish). Both genera were formerly thought to represent the distinct families Lepidosirenidae and Prot ...

, which still lives 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 sout ...

and

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

. The clade containing Gnathorhizidae and Lepidosirenidae is the crown group of the suborder

Ceratodontoidei Ceratodontoidei is a suborder of lungfish that is defined as "the clade including all taxa more closely related to ''South American lungfish, Lepidosiren'', ''Australian lungfish, Neoceratodus'' and ''Gnathorhiza'' than to ''Uronemus'', ''Conchop ...

, which also contains the extant family

Neoceratodontidae Neoceratodontidae is a family of lungfish containing the extant Australian lungfish and several extinct genera. It and Lepidosirenidae represent the only lungfish families still extant. Fossils from this family are first known from Triassic-aged ...

and many other extinct families.

Distribution

Gnathorhizids are found in North America, Eastern Europe, Australia, and Africa. Gnathorhizids from North America range from the Gzhelian through the

Roadian In the geologic timescale, the Roadian is an age or stage of the Permian. It is the earliest or lower of three subdivisions of the Guadalupian Epoch or Series. The Roadian lasted between and million years ago (Ma). It was preceded by the ...

. In Africa, gnathorhizids are found in

Olenekian In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian is sometimes divided i ...

of Madagascar and possibly South Africa. Lungfish

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...

attributed to gnathorhizids have been reported from the

Lopingian The Lopingian is the uppermost series/last epoch of the Permian. It is the last epoch of the Paleozoic. The Lopingian was preceded by the Guadalupian and followed by the Early Triassic. The Lopingian is often synonymous with the informal terms l ...

to the Olenekian in Poland and Western Russia. It is likely, then, that gnathorhizids had a

Pangea Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...

n distribution throughout the late

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

and early

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

Paleoecology and behavior

Gnathorhizids are found primarily in

paleosol In the geosciences, paleosol (''palaeosol'' in Great Britain and Australia) is an ancient soil that formed in the past. The precise definition of the term in geology and paleontology is slightly different from its use in soil science. In geolo ...

s representing

ephemeral Ephemerality (from the Greek word , meaning 'lasting only one day') is the concept of things being transitory, existing only briefly. Academically, the term ephemeral constitutionally describes a diverse assortment of things and experiences, fr ...

wetlands. Additionally, gnathorhizids, unlike most groups of fossil lungfish, are often found in association with regular burrow structures, suggesting this group of lungfish may have estivated during the dry season, much like modern African and

South American 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 southe ...

lungfish. Unlike most fossil lungfish, but again, like modern South American and African lungfish, gnathorhizids have bladelike toothplates. This suggests gnathorhizids were active predators unlike most lungfish, which feed primarily on benthic

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordat ...

References

Sources

* Berman, D. S., 1976, ''Cranial morphology of the Lower Permian lungfish Gnathorhiza (Osteichthyes: Dipnoi): Journal of Paleontology'', v. 50(6), p. 1020-1033. * Cunningham, C. R. and Dickson, E. D III, 1996, ''Distributions of Kansas Permo-Carboniferous vertebrate assemblages as a function of wet and dry seasons: Transactions of the Kansas Academy of Science'', v. 99(1-2), p. 16-28. * Huttenlocker, A.K. ''et al.'', 2005, ''An earliest Permian nonmarine vertebrate assemblage from the Eskridge Formation, Nebraska: * Lucas, S.G. and Zeigler, K.E., eds., 2005, ''The Nonmarine Permian, New Mexico Museum of Natural History and Science Bulletin No. 30''., pp. 133–143. {{Taxonbar, from=Q16982395 Prehistoric lungfish Prehistoric lobe-finned fish families Middle Triassic extinctions Pennsylvanian first appearances