传统观念认为，恐龙只会在白天活动，美国研究人员14日公布的研究成果挑战了这一观念。他们完成的一项对相关动物眼睛形状所做的研究显示，恐龙中也有“夜猫子”。
加利福尼亚大学戴维斯分校的研究人员对164种现存哺乳动物、爬行动物和鸟类的眼睛进行了分析，并判定了其活动模式与眼睛结构的关系。这些动物的活动模式分为白天型、夜间型、24小时中随时活动的无定时型。研究人员发现，白天活动的动物的眼部巩膜环开口较小，而夜间活动的动物开口较大。
研究人员接着分析了来自33种恐龙的化石，并根据它们的眼睛结构特征来推断其活动模式。他们发现，翼龙等飞行动物大多在白天活动，食肉恐龙大多在夜间活动，有些可能在夜间还很活跃，而食草恐龙大多是无定时活动的动物。
据研究人员介绍，因电影《侏罗纪公园》而名声大噪的速龙很可能就是“夜猫子”，而凶猛的食肉动物霸王龙是否夜间活动目前仍无法下结论，因为迄今尚未出土保存完好的霸王龙眼部化石。
上述研究成果15日发表在美国新一期《科学》杂志上。（生物谷Bioon.com）
生物谷推荐原文出处：
Science, 14 April 2011 DOI: 10.1126/science.1200043
Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology
Lars Schmitz and Ryosuke Motani
Variation in daily activity patterns facilitates temporal partitioning of habitat and resources among species. Knowledge of temporal niche partitioning in paleobiological systems has been limited by the difficulty of obtaining reliable information about activity patterns from fossils. On the basis of an analysis of scleral ring and orbit morphology in 33 archosaurs, including dinosaurs and pterosaurs, we show that the eyes of Mesozoic archosaurs were adapted to all major types of diel activity (that is, nocturnal, diurnal, and cathemeral) and provide concrete evidence of temporal niche partitioning in the Mesozoic. Similar to extant amniotes, flyers were predominantly diurnal; terrestrial predators, at least partially, nocturnal; and large herbivores, cathemeral. These similarities suggest that ecology drives the evolution of diel activity patterns.
