The Mangrullo Formation is an

Early Permian 01 or '01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * 01'' (Richard Müller album), 2001 * ''01'' (Son of Dave album), 2000 * ''01'' (Urban Zakapa album), 2011 * ''O1'' (Hiroyuki Sawano ...

(

Artinskian In the geologic timescale, the Artinskian is an age or stage of the Permian. It is a subdivision of the Cisuralian Epoch or Series. The Artinskian likely lasted between and million years ago (Ma) according to the most recent revision of th ...

) fossiliferous

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

in northeastern

Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

.Mangrullo Formation
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cre ...

.orgMangrullo Member
at

.org Some authors alternatively group it together with the

Paso Aguiar Formation Paso or PASO may refer to: People * Fernando del Paso (born 1935), Mexican novelist * Juan José Paso, (1758–1833), Argentine politician Other uses * Paso (float), an elaborate float made for religious processions * Paso (theatre), a seventee ...

and the Fraile Muerto Formation as the three

subdivisions Subdivision may refer to: Arts and entertainment * Subdivision (metre), in music * ''Subdivision'' (film), 2009 * "Subdivision", an episode of ''Prison Break'' (season 2) * ''Subdivisions'' (EP), by Sinch, 2005 * "Subdivisions" (song), by Rush ...

of the

Melo Formation Melo may refer to: People: *Melo (nickname) *Melo (surname), a Portuguese surname *Melo (Italian) or Melus of Bari, 11th century Apulian aristocrat Places: * Melo, Córdoba, a settlement in the Presidente Roque Sáenz Peña Department, Argentina ...

, in which case it is referred to as the Mangrullo Member.Beri et al., 2011 Like the correlated formations of Irati and Whitehill, it is known for its abundant

mesosaur Mesosaurs ("middle lizards") were a group of small aquatic reptiles that lived during the early Permian period, roughly 299 to 270 million years ago. Mesosaurs were the first known aquatic reptiles, having apparently returned to an aquatic lif ...

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. It also contains the oldest known '' Konservat-Lagerstätte'' 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 souther ...

, as well as the oldest known fossils of amniote

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...

Geology

The Mangrullo Formation is part of the Cerro Largo Group of the

Paraná Basin The Paraná Basin ( pt, Bacia do Paraná, es, Cuenca del Paraná) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande ...

infill In urban planning, infill, or in-fill, is the rededication of land in an urban environment, usually open-space, to new construction. Infill also applies, within an urban polity, to construction on any undeveloped land that is not on the urban mar ...

Radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares t ...

and

assemblage correlation with the

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

ian

Irati Formation Irati Formation is the name of a geological formation of the Paraná Basin in Brazil. It has previously been dated as Late Permian using palynomorphs, but is now dated as Early Permian using zircon ages obtained from bentonite layers. The base of ...

and the

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

n and

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and e ...

n Whitehill Formation, of the Paraná Basin and Karoo Basin respectively, puts it at around the

Age (about 279 ± 6

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

). It has a thickness of nearly .De Santa Ana et al., 2006 It consists primarily of beds of variable thickness of sandy and

dolomitic Dolomite () is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dol ...

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

and

laminated Lamination is the technique/process of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance, or other properties from the use of the differing material ...

oil shale Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitu ...

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

, and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

.Piñeiro et al., 2012a

Fossil biota

Fossil plants found in the formation include

petrified In geology, petrifaction or petrification () is the process by which organic material becomes a fossil through the replacement of the original material and the filling of the original pore spaces with minerals. Petrified wood typifies this proce ...

wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of ligni ...

and other remains from

conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...

seed fern A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...

s (notably '' Gangamopteris''), and various palynomorphs. Invertebrate fossils include

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...

clam shrimp Clam shrimp are a group of bivalved branchiopod crustaceans that resemble the unrelated bivalved molluscs. They are extant and also known from the fossil record, from at least the Devonian period and perhaps before. They were originally classifi ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...

wings ( Hemiptera and

Coleoptera Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

of '' Paracicadopsis mendezalzolai'', '' Barona arcuata'' and '' Perlapsocus formosoi''),Pinto et al., 2000

pygocephalomorph The order Pygocephalomorpha is an extinct group of peracarid crustaceans. Pygocephalomorpha were abundant from the Carboniferous until their extinction in the Permian. Families The order contains extinct five families, and seven genera ''incer ...

s, and ''

Chondrites A chondrite is a stony (non-metallic) meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primi ...

''. Vertebrate fossils include fragmentary remains of

actinistia The coelacanths ( ) are fish belonging to the order Actinistia that includes two Extant taxon, extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off t ...

ns (coelacanths) and

actinopterygians Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...

(tentatively identified as belonging to Elonichthyidae), possible

ichnofossil A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...

s of

acanthodians Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which ...

('' Undichna insolentia''), and numerous and well-preserved skulls and partial skeletons of

s (''

Stereosternum ''Stereosternum tumidum'' (meaning "rigid chest") (Stereos, Greek: “solid, firm”; Sternon, Greek: “chest, breastbone”) is an extinct genus of mesosaur marine reptile from the Early Permian of Brazil and also the Great Karoo Basin of Sout ...

'' and ''

Mesosaurus ''Mesosaurus'' (meaning "middle lizard") is an extinct genus of reptile from the Early Permian of southern Africa and South America. Along with it, the genera ''Brazilosaurus'' and '' Stereosternum'', it is a member of the family Mesosauridae ...

'').Mones, 1972 The Mangrullo Formation is notable for being the oldest known '' Konservat-Lagerstätte'' in

. Fossils in some layers are exceptionally preserved, retaining details of soft tissue (including bone sutures, blood vessels, and nerves).

Coprolite A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name is de ...

s and gut contents of mesosaurs reveal that they preyed mainly on pygocephalomorph

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

s and may have engaged in

cannibalism Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...

. It is also the source of several fossil

s, a

hatchling In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. A group of mammals called monotremes lay eggs, and their young are hatchlings as well. Fish Fish hatchlings generally do not receive parental care, similar ...

, and very small mesosaurids; all of which are the oldest known evidence of amniotic

ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the stu ...

.Piñeiro et al., 2012b

Taphonomy

The locality is believed to have been a shallow

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into '' coastal lagoons'' (or ''barrier lagoons' ...

-like

inland sea An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large and is either completely surrounded by dry land or connected to an ocean by a river, strait, or "arm of the sea". An inland s ...

. Its early conditions were probably

estuarine An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

, and the fossils found in the lower mudstone and claystone layers are of bioturbating invertebrates, bivalves and fish. It had an open coastal barrier to marine water but also had extensive inflow of freshwater from melting glaciers. Overlying the earlier mudstone and claystone layers is a layer of limestone deposited with noticeable rippling, an effect of wave motion on very shallow sediment. It is believed that the connection to the sea was lost and the basin gradually began to dry out, becoming more and more

hypersaline A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride, brines, and other salts, with saline levels surpassing that of ocean water (3.5%, i.e. ). Specific microbial species can thrive in hig ...

as it became shallower. It produced

anoxic The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of diss ...

conditions near the bottom which resulted in the exceptional preservation of fossils during this period. Most of the earlier organisms disappeared and was replaced by mesosaurs and pygocephalomorphs, both inferred to have been capable of tolerating hypersaline environments. The connection to the sea was reestablished later on in the top layers, and fossils of mesosaurs disappeared to be replaced once again by fish and bioturbating organisms.

Gallery

280 Ma plate tectonic reconstruction.png, Early Permian paleogeography Mangrullo Formation Mesosaurus tenuidens.jpg, ''Mesosaurus tenuidens'' Mangrullo Formation Mesosaurus tenuidens 2.jpg, ''M. tenuidens'' Mangrullo Formation mesosaurid fossils.jpg, Mesosaurid fossils Mangrullo Formation mesosaurid palate.jpg, Mesosaurid palate Mangrullo Formation mesosaurid skull.jpg, Mesosaurid skull Mesosaurus sea.png, "''Mesosaurus'' Sea" Mangrullo Formation mesosaurid skull and description.jpg, Mesosaurid skull and description Mangrullo Formation mesosaurid skeleton and gypsum.jpg, Mesosaurid skeleton and gypsum Mangrullo Formation pygocephalomorph fossils.jpg, Pygocephalomorph fossils Mangrullo Formation pygocephalomorph fossils 2.jpg, Pygocephalomorph fossils Mangrullo Formation algal mats.jpg, Algal mats Stereosternum.jpg, Artist's reconstruction of ''

References

Bibliography