Муссазавр: Ранний зауроподоморф из Аргентины

Extinct genus of dinosaurs

Mussaurus (meaning "mouse lizard") is a genus of herbivorous sauropodomorph dinosaur that lived in southern Argentina during the Sinemurian stage of the Early Jurassic. It receives its name from the small size of the skeletons of juvenile and infant individuals, which were once the only known specimens of the genus. However, since Mussaurus is now known from adult specimens, the name is something of a misnomer. In its early stages of life, Mussaurus was a small quadrupedal herbivore, walking on all four legs. As it grew up, the changes in body proportions may have led its centre of mass to move backwards towards its pelvis. Adults would have been medium sized bipedal herbivores, measuring up to long and weighing up to
Numerous specimens of varying age found in a single locality suggest that Mussaurus is one of the earliest dinosaurs to have lived in a gregarious lifestyle. With its possible origin from the Triassic, this complex social behaviour may have given rise to the sauropods' early success as the largest herbivores on land. Mussaurus also possessed anatomical features that suggest a close, possibly transitional evolutionary relationship with true sauropods.

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.

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). It is estimated that Mussaurus would have been sexually mature at 23 to 31 years of age, and reached somatic maturity after 14 years.