Featured Research

from universities, journals, and other organizations

The eyes have it: Dinosaurs hunted by night

Date:
April 15, 2011
Source:
University of California - Davis
Summary:
The movie Jurassic Park got one thing right: those velociraptors hunted by night while the big plant-eaters browsed around the clock, according to a new study of the eyes of fossil animals.

The pterosaur Scaphognathus crassirostris was a day-active, flying archosaur. Scleral ring highlighted.
Credit: Lars Schmitz/UC Davis

The movie Jurassic Park got one thing right: Those velociraptors hunted by night while the big plant-eaters browsed around the clock, according to a new study of the eyes of fossil animals. The study will be published online April 14 in the journal Science.

This conclusion overturns the conventional wisdom that dinosaurs were active by day while early mammals scurried around at night, said Ryosuke Motani, professor of geology at UC Davis and co-author of the paper.

"It was a surprise, but it makes sense," Motani said.

The research is 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 in the Department of Evolution and Ecology at UC Davis.

Motani and Schmitz, a former graduate student of Motani's, worked out the dinosaur's daily habits by studying their eyes.

Dinosaurs, lizards and birds all have a bony ring called the "scleral ring" in their eye, a structure that 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. They took the same measurements in 164 living species.

Day-active, or diurnal, animals have a small opening in the middle of the ring. In nocturnal animals, the opening is much larger. Cathemeral animals -- active both day and night -- tend to be in between.

The size of these features is affected by a species' environment (ecology) as well as by ancestry (phylogeny). For example, two closely related animals might have a similar eye shape even though one is active by day and the other by night: The shape of the eye is constrained by ancestry.

Schmitz and Motani wrote a computer program to separate the "ecological signal" from the "phylogenetic signal." The results of that analysis are in a separate paper published simultaneously in the journal Evolution.

By looking at 164 living species, the UC Davis team was able to confirm that eye measurements are quite accurate in predicting whether animals are active by day, by night or around the clock.

They then applied the technique to fossils from plant-eating and carnivorous dinosaurs, flying reptiles called pterosaurs, and ancestral birds.

The measurements revealed that 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 needed to avoid overheating. Modern megaherbivores like elephants show the same activity pattern, Motani said.

Velociraptors and other small carnivores were night hunters, Schmitz and Motani showed. They were not able to study big carnivores such as Tyrannosaurus rex, because there are no fossils with sufficiently well-preserved scleral rings.

Flying creatures, including early birds and pterosaurs, were mostly day-active, although some of the pterosaurs -- including a filter-feeding animal that probably lived rather like a duck, and a fish-eating pterosaur -- were apparently night-active.

The ability to separate out the effects of ancestry gives researchers a new 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 funded by the National Science Foundation and a postdoctoral fellowship from the Deutsche Forschungsgemeinschaft (Germany) to Schmitz.


Story Source:

The above story is based on materials provided by University of California - Davis. Note: Materials may be edited for content and length.


Journal Reference:

  1. Lars Schmitz and Ryosuke Motani. Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology. Science, 14 April 2011 DOI: 10.1126/science.1200043

Cite This Page:

University of California - Davis. "The eyes have it: Dinosaurs hunted by night." ScienceDaily. ScienceDaily, 15 April 2011. <www.sciencedaily.com/releases/2011/04/110414141354.htm>.
University of California - Davis. (2011, April 15). The eyes have it: Dinosaurs hunted by night. ScienceDaily. Retrieved August 27, 2014 from www.sciencedaily.com/releases/2011/04/110414141354.htm
University of California - Davis. "The eyes have it: Dinosaurs hunted by night." ScienceDaily. www.sciencedaily.com/releases/2011/04/110414141354.htm (accessed August 27, 2014).

Share This




More Fossils & Ruins News

Wednesday, August 27, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

40,000-Year-Old Mammoth Skeleton Found On Texas Farm

40,000-Year-Old Mammoth Skeleton Found On Texas Farm

Newsy (Aug. 26, 2014) — A mammoth skeleton was discovered in a gravel pit on Wayne McEwen's Texas farm back in May. It's now being donated to a museum. Video provided by Newsy
Powered by NewsLook.com
Pawn Shop Buys Lincoln Signature For $50, Worth $50,000

Pawn Shop Buys Lincoln Signature For $50, Worth $50,000

Newsy (Aug. 25, 2014) — The signature is one of a couple Lincoln autographs that have popped up recently. Video provided by Newsy
Powered by NewsLook.com
Neanderthals Probably Died Out Earlier Than We Thought

Neanderthals Probably Died Out Earlier Than We Thought

Newsy (Aug. 21, 2014) — A new study is packed with interesting Neanderthal-related findings, including a "definitive answer" to when they went extinct. Video provided by Newsy
Powered by NewsLook.com
Disquieting Times for Malaysia's 'fish Listeners'

Disquieting Times for Malaysia's 'fish Listeners'

AFP (Aug. 19, 2014) — Malaysia's last "fish listeners" -- practitioners of a dying local art of listening underwater to locate their quarry -- try to keep the ancient technique alive in the face of industrial trawling and the depletion of stocks. Duration: 02:29 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins