Early Jurassic (215Ma) dinosaur from southern Argentina; originally thought to have been from the Late Triassic. Eggs and hatchlings were discovered in the 1970s, but adults were not described until 2013. There is now a good record of their growth series from babies (20cm long) to juveniles and adults (up to 6m long; >1000 kg).
Large, robust and probably bipedal as adults, and herbivorous. Young Mussaurus may have been quadrupedal (arms and legs are similar sizes; unlike adults).
Mussaurus was a sauropodomorph, and like the later sauropods (e.g. Diplodocus) that it was a close cousin to, had a long neck and long tail. It thus helps to reveal how sauropodomorphs began to become transform into animals more similar to the giant sauropods across the Triassic-Jurassic transition.