Despite dominating biodiversity in the Mesozoic, dinosaurs were not speciose. Oviparity constrained even gigantic dinosaurs to less than 15 kg at birth; growth through multiple morphologies led to the consumption of different resources at each stage. Such disparity between neonates and adults could have influenced the structure and diversity of dinosaur communities. Here, we quantified this effect for 43 communities across 136 million years and seven continents. We found that megatheropods (more than 1000 kg) such as tyrannosaurs had specific effects on dinosaur community structure. Although herbivores spanned the body size range, communities with megatheropods lacked carnivores weighing 100 to 1000 kg. We demonstrate that juvenile megatheropods likely filled the mesocarnivore niche, resulting in reduced overall taxonomic diversity. The consistency of this pattern suggests that ontogenetic niche shift was an important factor in generating dinosaur community structure and diversity.

尽管在中生代占据着生物多样性的主导地位，但恐龙并不是特异的。卵生甚至将巨大的恐龙限制在出生时不到 15 公斤；通过多种形态的增长导致每个阶段消耗不同的资源。新生儿和成年人之间的这种差异可能影响了恐龙群落的结构和多样性。在这里，我们对跨越 1.36 亿年和七大洲的 43 个社区的这种影响进行了量化。我们发现霸王龙等巨型兽脚类动物（超过 1000 公斤）对恐龙群落结构具有特定的影响。尽管食草动物跨越了体型范围，但拥有巨型兽脚类动物的社区缺乏体重 100 至 1000 公斤的食肉动物。我们证明，幼年巨兽足类动物可能充满了中肉食动物生态位，导致整体分类多样性降低。