Microsauria is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

, possibly polyphyletic

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

s from the late

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

and early

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

periods. It is the most diverse and species-rich group of

lepospondyl Lepospondyli is a diverse clade of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco ('' Diplocaulus minimus''), lepospondyls lived from the Visean stage of the Early Carboniferous to the Earl ...

s. Recently, Microsauria has been considered

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

, as several other non-microsaur lepospondyl groups such as Lysorophia seem to be nested in it. Microsauria is now commonly used as a collective term for the grade of lepospondyls that were originally classified as members of Microsauria. The microsaurs all had short tails and small legs, but were otherwise quite varied in form. The group included lizard-like animals that were relatively well-adapted to living on dry land, burrowing forms, and others that, like the modern

axolotl The axolotl (; from ) (''Ambystoma mexicanum'') is a neoteny, paedomorphic salamander, one that Sexual maturity, matures without undergoing metamorphosis into the terrestrial adult form; adults remain Aquatic animal, fully aquatic with obvio ...

, retained their gills into adult life, and so presumably never left the water. Their skeleton was heavily ossified, and their development was likely gradual with no metamorphosis.

Distribution

Microsaur remains have been found from

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

in Late Carboniferous and Early Permian localities. Most North American microsaurs have been found in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...

, as well as Kansas and

Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...

, although remains have also been found in

Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...

. In Europe, microsaurs are known from

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

and the

Czech Republic The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the south ...

. Possible microsaur remains have also been found from strata in the town of

Vyazniki Vyazniki () is the name of several types of inhabited localities in Russia, inhabited localities in Russia. ;Urban localities *Vyazniki, Vladimir Oblast, a town in Vyaznikovsky District of Vladimir Oblast ;Rural localities *Vyazniki, Samara Oblast ...

in the

Vladimir Oblast Vladimir Oblast () is a federal subject of Russia (an oblast). Its administrative center is the city of Vladimir, which is located east of Moscow. As of the 2010 Census, the oblast's population was 1,443,693. The UNESCO World Heritage L ...

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

. These strata are

Late Permian Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...

in age, near the Permo-Triassic boundary. The microsaur material at Vyazniki may be the youngest record of microsaurs, and would extend their range by around 20 million years. However, fossil remains from

Gansu Province Gansu is a provinces of China, province in Northwestern China. Its capital and largest city is Lanzhou, in the southeastern part of the province. The seventh-largest administrative district by area at , Gansu lies between the Tibetan Plateau, Ti ...

shows possible

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

record of microsaur.

Classification

Cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

modified from Anderson (2001), with microsaur taxa marked with : Cladogram from Ruta and Coates (2007): Cladistic analysis by Pardo et al. (2017) places

recumbirostra Recumbirostra is a clade of tetrapods which lived during the Carboniferous and Permian periods. They are thought to have had a fossorial (burrowing) lifestyle and the group includes both short-bodied and long-bodied snake-like forms. At least one ...

n microsaurs and lysorophians as members of

Amniota Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the C ...

References

External links

Microsauria
in the

Paleobiology Database The Paleobiology Database (PBDB) is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database originated in the NCEAS-funded Phanerozoic Marine Pale ...

{{Authority control Prehistoric tetrapod orders Pennsylvanian first appearances Cisuralian extinctions