Stephen Spielberg's movie Jurassic Park got one thing right.
Velociraptors hunted by night while big plant-eating dinosaurs browsed around the clock, according to a paper on the eyes of fossil animals published on-line this week in Science Express.
That overturns the conventional wisdom that dinosaurs were active by day while early mammals scurried around at night, said Ryosuke Motani, a geologist at the University of California at Davis, and a co-author of the paper.
"It was a surprise, but it makes sense," Motani said.
It's also providing insight into how ecology influences the evolution of animal shape and form over tens of millions of years, according to Motani and collaborator Lars Schmitz, a postdoctoral researcher at UC Davis.
"These authors' conclusion that these dinosaurs were active diurnally and nocturnally challenges a general dogma--that nocturnality in that time was mostly restricted to mammals," says H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.
Motani and Schmitz worked out the dinosaurs' daily habits by studying their eyes.
Dinosaurs, lizards and birds all have a bony ring called the "scleral ring" in their eyes, although this is lacking in mammals and crocodiles.
Schmitz and Motani measured the inner and outer dimensions of this ring, plus the size of the eye socket, in 33 fossils of dinosaurs, ancestral birds and pterosaurs--and in 164 living species.
Day-active, or diurnal animals have a small opening in the middle of the ring while the opening is much larger in nocturnal animals.
Cathemeral animals--active in both day and night--tend to be in between.
But the size of these features is also affected by ancestry.
For example, two closely related animals might have similar eye shape even if one is active by day and the other by night: the shape of the eye is constrained by ancestry, and that could bias the results.
Schmitz and Motani developed a computer program to separate the "ecological signal" from this "phylogenetic signal."
The results of that analysis are in a separate paper published simultaneously in the journal Evolution.
By looking at a 164 living species, they could confirm that the eye measurements were accurate in predicting whether animals were active by day, by night or around the clock.
Then they applied the technique to fossils, including plant-eating and carnivorous dinosaurs, flying reptiles called pterosaurs and ancestral birds.
The big plant-eating dinosaurs were active day and night, probably because they had to eat most of the time, except for the hottest hours of the day when they avoided overheating.
Modern megaherbivores like elephants show the same activity pattern, Motani said.
Velociraptors and other small carnivores were night hunters.
Schmitz and Motani were not able to study big carnivores such as Tyrannosaurus rex, because there are no fossils with sufficiently well-preserved eyes.
Flying creatures, including early birds and pterosaurs, were mostly day-active, although some of the pterosaurs--including a filter-feeding animal that probably lived like a duck, and a fish-eating pterosaur--were apparently night-active.
"This strongly suggests that ecology drives activity," Schmitz said.
By separating out the effects of ancestry, researchers now have a tool to understand how animals lived in their environment and how changes in the environment influenced their evolution over millions of years, Motani said.
The work was also funded a postdoctoral fellowship from the German government (DFG).Media Contacts
Cheryl Dybas | EurekAlert!
AWI researchers measure a record concentration of microplastic in arctic sea ice
24.04.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
Climate change in a warmer-than-modern world: New findings of Kiel Researchers
24.04.2018 | Christian-Albrechts-Universität zu Kiel
Magnetic resonance imaging, or MRI, is a widely used medical tool for taking pictures of the insides of our body. One way to make MRI scans easier to read is...
At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.
Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...
Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.
Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
26.04.2018 | Power and Electrical Engineering
26.04.2018 | Life Sciences
26.04.2018 | Power and Electrical Engineering