Mussaurus

Infant and juvenile fossils of Mussaurus were first discovered by an expedition led by Jose Bonaparte during the 1970s to the Laguna Colorada Formation, where the team found fossilized eggs and hatchlings, which added insight into the reproductive strategies of Mussaurus and other sauropodomorph dinosaurs. The age of the formation is estimated between 192.78 ± 0.14 Ma and 192.74 ± 0.14 Ma. The first adult specimens of Mussaurus were described in 2013, although some of these specimens had first been described in 1980 and were originally attributed to the genus Plateosaurus. ==Classification==

Previous to the discovery of adult specimens of Mussaurus, the phylogenetic position of this taxon was difficult to establish. Infant and juvenile fossils are known to show more basal traits than adult specimens of the same taxon. Furthermore, the recently discovered of one subadult and three adult specimens assigned to Mussaurus are more complete than other material assigned to it. Therefore, a cladistic analysis of basal sauropodomorphs performed by Otero and Pol (2013) to test the phylogenetic relationships of Mussaurus, included information only from adult specimens. The following cladogram is simplified after their analysis (relationships outside Plateosauria are not shown). }} }} ==Palaeobiology==

Mussaurus specimens have been found in association with nests that are believed to contain multiple eggs apiece. The skeletons of Mussaurus infants were small, measuring about long and weighing about . but both authors with Anusuya Chinsamy subsequently argued in 2014 that this tissue most likely represents a pathologically formed tissue instead based on histological features. Social behaviour As of 2021, Mussaurus represents the earliest unequivocal evidence of complex social behaviour in dinosaurs, with over 100 eggs and skeletal specimens of 80 individuals ranging from embryos to adults found in the same locality. This discovery predates the previous records of herd-living dinosaurs by at least 40 million years. It is thought that this behaviour has been originated from the Triassic period, leading them to become successful as large terrestrial herbivores. It is estimated that Mussaurus would have been sexually mature at 23 to 31 years of age, and reached somatic maturity after 14 years. == References ==