Earliest evidence of herd-living and age segregation amongst
dinosaurs.

Abstract

Sauropodomorph dinosaurs dominated the herbivorous niches during the
first 40 million years of dinosaur history (Late Triassic–Early
Jurassic), yet palaeobiological factors that influenced their
evolutionary success are not fully understood. For instance, knowledge
on their behaviour is limited, although herding in sauropodomorphs has
been well documented in derived sauropods from the Late Jurassic and
Cretaceous. Here we report an exceptional fossil occurrence from
Patagonia that includes over 100 eggs and skeletal specimens of 80
individuals of the early sauropodomorph Mussaurus patagonicus, ranging
from embryos to fully-grown adults, with an Early Jurassic age as
determined by high-precision U–Pb zircon geochronology. Most specimens
were found in a restricted area and stratigraphic interval, with some
articulated skeletons grouped in clusters of individuals of
approximately the same age. Our new discoveries indicate the presence
of social cohesion throughout life and age-segregation within a herd
structure, in addition to colonial nesting behaviour. These findings
provide the earliest evidence of complex social behaviour in
Dinosauria, predating previous records by at least 40 My. The presence
of sociality in different sauropodomorph lineages suggests a possible
Triassic origin of this behaviour, which may have influenced their
early success as large terrestrial herbivores.

Open access:
https://www.nature.com/articles/s41598-021-99176-1