Some species of dinosaurs and ancient flying reptiles probably foraged at night, suggests a new fossil study of bony structures found in the eyes of many reptiles and birds. In modern creatures that have such structures, the sizes and proportions of these so-called scleral rings which reinforce the eye's outer tissues and surround the pupil, are reliable indicators of whether the animals are active during the day, night, or both. The relatively small size and internal diameter of the scleral ring in the falcon-sized pterosaur Scaphognathus crassirostris (depicted in purple, main image), compared to the size of the creature's eye socket, indicate that this flying reptile could see well only in bright light, researchers report online today in Science. However, the large internal and external diameters of the scleral ring in the toothy, retriever-sized Velociraptor mongoliensis (top image) suggest that the predator hunted at night. Although most flying reptiles analyzed for the study were active in daytime, four of the pterosaurs were apparently nocturnal and occupied ecological niches similar to those of today's bats. The findings defy the common wisdom that ancient mammals skulked about unbothered by predators presumed to have been active only in the daytime.
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