Dinosaurs that lived in age-segregated groups

Young diplodocid dinosaurs may have lived separately from their parents, eaten more vegetables and even shown some physical differences, new research suggests.

Studies of the smallest diplodocid skull yet discovered show that juveniles were not just mini versions of their parents. In fact, some of their features were more like those of their ancestors – an evolutionary phenomenon known as recapitulation.

As they grew, their features changed into the derived states found in adults. This, note researchers led by Cary Woodruff from Canada’s University of Toronto, underlines the need for caution when identifying and naming new discoveries.

Diplodocids, which include long-necked herbivores such as the Brontosaurus, are among the best known of the sauropods, the largest terrestrial vertebrates.

The small skull examined by Woodruff and colleagues has a cranial length of just 24 centimetres, and was among an assemblage of small diplodocid sauropods found in Montana in the US.  It was an important discovery, because cranial remains have been rare, complicating attempts to understand their paleobiology.

In a paper published in the journal Scientific Reports, the scientists say the juvenile’s short, narrow snout suggests its diet may have included a broader variety of plant materials than that of adults, which had wide and squared snouts.

Juveniles also may have fed in forests rather than in the more open habitats where adults browsed at ground level for their specialised diets, suggesting that life was lived in age-segregated herds.

The authors argue that the findings could provide evidence for the lack of parental care in diplodocid dinosaurs. There may be good reasons for that, however.

Given the extreme size difference between hatchlings and adults, separation may have protected infants from being trampled. The forest habitat may also have shielded them from predators.