浙江天台上白垩统赤城山组中发掘出属伤齿龙类的棱柱形蛋化石。研究认为，棱柱形蛋从伤齿龙类恐龙中产出就具有较高刚度的蛋壳，可直接插入松软的泥沙里，明显区别于其他大多数恐龙及现代爬行类所产的韧性蛋壳蛋，韧性蛋壳的恐龙蛋往往因重力作用产生变形而呈扁球形和扁椭球形。伤齿龙类的棱柱形蛋的刚性蛋壳很接近现代鸟蛋的蛋壳，暗示伤齿龙类恐龙生殖系统在蛋壳形成方面与现代鸟类有一定相似性。同时，伤齿龙类的棱柱形蛋或多或少地以向外倾斜的形式排布，反映出伤齿龙类恐龙产卵时可能面向巢穴外，是一种对生存环境的适应行为。

The unique nesting and egg-laying behaviors of troodontids differ from those of other dinosaurs in that troodontids laid their eggs standing up in sands or muddy soil.The clutches of fossil troodontid eggs have been unearthed from the Mid-Upper Cretaceous sedimentary sequences in Inner Mongolia,Henan and Guangdong.The fossil skeletons of troodontid were found in the Lower Cretaceous strata of Inner Mongolia and Liaoning provinces.Here,we describe a clutch of fossil troodontid eggs in the Cretaceous Chichengshan Formation from Tiantai Basin,Zhejiang Province.The specimens we discovered indicate that the troodontid egg-shell was as rigid as that of some modern bird eggs and was sufficiently strong to resist the pressure while the egg was forced into sands and muddy soil when it was laid.Most other dinosaur eggshells,in contrast,were stretchable as some modern reptile eggs.Dinosaur eggs with stretchable egg-shell are preserved as flattened,circular or oval in outline.In other words,the procreant system of troodontid resembled,to some extent,some modern birds in egg-shell formation.More-over,the troodontid eggs in nest stood aslant more or less outwards.This suggested that an adult female troodontid faced outwards while laying eggs vigilantly.This behavior could be an adaptation to severe competition.

Q91

国家自然科学基金，中国地质调查局基础地质调查综合研究项目