''Macrocollum'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of unaysaurid

sauropodomorph Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had l ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

that lived during the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

period (early

Norian The Norian is a division of the Triassic Period. It has the rank of an age ( geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian. Stratigraphic ...

) in what is now

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 ...

. It is one of the oldest dinosaurs known.

Discovery

''Macrocollum'' was discovered in 2012 in Rio Grande do Sul, Brazil, at the Wachholz site of the Candelária Formation, Paraná Basin. It was announced in a press conference on November 21, 2018. The generic name combines the Greek word μακρός (long) and the Latin word ''collum'' (neck), referring to the animal's elongated neck. The specific epithet honours José Jerundino Machado Itaqui, one of the main persons behind the creation of CAPPA/UFSM.

Description

Like most early dinosaurs, ''Macrocollum'' was relatively small, and walked on

two legs In sports (particularly association football), a two-legged tie is a contest between two teams which comprises two matches or "legs", with each team as the home team in one leg. The winning team is usually determined by aggregate score, the sum ...

The known remains of ''Macrocollum'' are relatively well preserved. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

specimen consists of an almost complete and articulated skeleton. The two

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). O ...

specimens are both articulated skeletons with one missing a

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, t ...

and its cervical series. ''Macrocollum itaquii'' differs from all other known sauropodomorphs based on a unique combination of characters such as those found on the

, which include an antorbital fossa perforated by a promaxillary

fenestra A fenestra (fenestration; plural fenestrae or fenestrations) is any small opening or pore, commonly used as a term in the biological sciences. It is the Latin word for "window", and is used in various fields to describe a pore in an anatomical ...

, and a medial margin of the supratemporal fossa with a simple smooth curve at the frontal/parietal suture.

Classification

''Macrocollum'', alongside '' Jaklapallisaurus'' and '' Unaysaurus'', was found to belong to the clade Unaysauridae.

Paleoecology

''Macrocollum'' lived between about 225.42 to 225

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). ...

, in the

age of the late

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

period. It was found in the south of Brazil, which at the time was connected to northwest

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 ...

. At the time, most of the Earth's landmass was united into the supercontinent Pangaea, which was just starting to divide into

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pan ...

in the north, and

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final st ...

in the south. U-Pb (

Uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly ...

decay) dating found that the

Caturrita Formation The Caturrita Formation is a rock formation found in Rio Grande do Sul, Brazil. Its sediments were deposited in the Paraná Basin. The formation is from the Upper Triassic and forms part of the Santa Maria Supersequence in the upper section of the ...

, close to the holotype locality, dates to around 225.42 million years ago, making it fewer than 10 million years younger than the Santa Maria and Ischigualasto Formations, from where the earliest dinosaurs are known.

Studies

The ilia of one of the

s of ''Macrocollum'' (CAPPA/UFSM 0001b) were used as a model in a study on the taphonomical effects of sedimentary compression on the iliac morphology of early

sauropodomorphs Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had l ...

References

{{Taxonbar, from=Q58979887 Sauropodomorphs Late Triassic dinosaurs of South America Fossils of Brazil Paleontology in Rio Grande do Sul Triassic Brazil Fossil taxa described in 2018 Paraná Basin