【古生物学】ディプロドクス科恐竜のこれまでで最も小さな頭蓋骨から竜脚類恐竜の生活を解明する手掛かりが見つかる

Young diplodocid dinosaurs (long-necked herbivores such as the Brontosaurus) may have had different diets, shown different physical features, and lived in separate groups from their parents, a study in Scientific Reports suggests.

D. Cary Woodruff and colleagues examined the smallest diplodocid skull yet discovered - with a total cranial length of approximately 24cm - to reveal so far unknown aspects of immature diplodocid anatomy. Comparing the skull to other, larger specimens, the authors found that juveniles were not merely smaller versions of adults, but that they showed physical features that were more similar to those of their ancestors than those of their own, adult parents - a phenomenon known as recapitulation. As the dinosaurs grew, these features changed into the more recent (derived) states found in adults.

The unique features of the juvenile skull and teeth examined in the study provide insights into how diplodocid dinosaurs may have lived. The short, narrow snout suggests that the diet of juveniles may have included a wider variety of plant materials than that of adults, which had wide and squared snouts. The authors also suggest that juveniles may have fed in forests rather than in the more open habitats where adults browsed at ground level for their more specialist diets. They argue that the findings could provide evidence for the lack of parental care in diplodocid dinosaurs, whose offspring may have lived in forests as parts of age-segregated herds. Given the extreme size difference between hatchlings and adults, the separation of parents and offspring may have protected infants from being trampled while the juveniles’ forest habitat may also have shielded them from predators, the authors suggest.