| Macrocollum | |
|---|---|
 | |
| Skeletal reconstruction ofMacrocollum itaquii. Known elements in white and unknown in dark gray | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Unaysauridae |
| Genus: | †Macrocollum Mülleret al.,2018 |
| Species: | †M. itaquii |
| Binomial name | |
| †Macrocollum itaquii Mülleret al., 2018 | |
Macrocollum is agenus ofunaysauridsauropodomorphdinosaur that lived during theLate Triassicperiod (earlyNorian) in what is nowBrazil. It is one of the oldest dinosaurs known.[1]
Macrocollum was discovered in 2012 inRio Grande do Sul, Brazil, at the Wachholz site of theCandelária Formation, Paraná Basin.[2] It was announced in a press conference on November 21, 2018. The generic name combines the Greek word μακρός (long) and the Latin wordcollum (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.[1]
Like most early dinosaurs,Macrocollum was relatively small, and walked ontwo legs.
The known remains ofMacrocollum are relatively well preserved. Theholotype specimen consists of an almost complete and articulated skeleton. The twoparatype specimens are both articulated skeletons with one missing askull and itscervical series.[1]
Evidence for anair sac system has been documented in the fossils, and is the oldest known dinosaur with this trait.[3]
Macrocollum itaquii differs from all other known sauropodomorphs based on a unique combination of characters such as those found on theskull, which include an antorbitalfossa perforated by a promaxillaryfenestra, and a medial margin of the supratemporal fossa with a simple smooth curve at the frontal/parietalsuture.[1]
Macrocollum, alongsideJaklapallisaurus andUnaysaurus, was found to belong to the cladeUnaysauridae.[1]
Macrocollum lived between about 225.42 to 225 million years ago, in theNorianage of the lateTriassicperiod. It was found in the south of Brazil, which at the time was connected to northwestAfrica. At the time, most of the Earth's landmass was united into the supercontinent Pangaea, which was just starting to divide intoLaurasia in the north, andGondwana in the south.[4][5] U-Pb (Uranium decay) dating found that theCaturrita Formation, close to the holotype locality, dates to around 225.42 million years ago, making it fewer than 10 million years younger than theSanta Maria andIschigualasto Formations, from where the earliest dinosaurs are known.[6]
The ilia of one of theparatypes ofMacrocollum (CAPPA/UFSM 0001b) were used as a model in a study on thetaphonomical effects of sedimentary compression on the iliac morphology of earlysauropodomorphs.[7]
