Featured Research

from universities, journals, and other organizations

Not All Aerial Reptiles Were Level-headed, CT Scans Show; Inside View Of Pterosaurs’ Brain Yields Insights To Posture, Behavior

Date:
October 30, 2003
Source:
National Science Foundation
Summary:
A study released this week gives a clearer picture of what went on inside the pterosaur's head. When scientists using skull fossils examined the neuroanatomy responsible for flight control and prey spotting, they found key structures to be specialized and enlarged, a discovery that could revise views of how vision, flight, and the brain itself evolved.

ARLINGTON, Va. -- With its 13-foot wing span, a flying dinosaur soars above a lake, scanning for dinner as its shadow glides across the water's surface below. Eying a fish, the aerobatic reptile, called a pterosaur, dives through the air, its shadow shrinking and darkening until – splash! The fish is in the pterosaur's beak, which resembles a cross between a pelican's bill and a crocodile's snout.

While such a scene would have occurred more than 100 million years ago, a study released this week gives a clearer picture of what went on inside the pterosaur's head. When scientists using skull fossils examined the neuroanatomy responsible for flight control and prey spotting, they found key structures to be specialized and enlarged, a discovery that could revise views of how vision, flight, and the brain itself evolved.

The researchers, led by Lawrence Witmer of Ohio University, took a high-tech look through two skulls of separate species of pterosaurs. Using computerized images derived from X-rays, they peered into the vestibular apparatus, the passageways and chambers responsible for maintaining equilibrium. They also dove "virtually" into the brain cavity to analyze the regions responsible for coordinating wing movements, for scanning the environment, and for "stabilizing gaze," a necessity for airborne predators.

The scientists report their findings in the Oct. 30 issue of the journal Nature. The research team also included Sankar Chatterjee of the Museum of Texas Tech University and Jonathan Franzosa and Timothy Rowe from the University of Texas (UT) at Austin. The trio put the two skulls through the scanner at UT's High-Resolution X-ray Computed Tomography Facility.

The research was supported by the Division of Integrative Biology and Neurosciences of the National Science Foundation (NSF), the independent federal agency that supports fundamental research and education across all fields of science and engineering.

According to William Zamer, who directs NSF's Ecological and Evolutionary Physiology program, "It is a beautifully integrative study: It uses paleontological information, state-of-the-art technology to reconstruct the brain anatomies, and existing knowledge of the working of the semicircular canals to draw fascinating inferences about how these organisms may have performed when they were alive."

Some differences between the two pterosaurs were outwardly apparent.

The skull of Rhamphorhynchus muensteri, a species found in Jurassic formations in Germany, is about five inches long. From its broad back, the skull tapers steadily to a pointed beak.

The skull of Anhanguera santanae, found in the Cretaceous deposits of Brazil, is almost two feet long. Narrower and triangular in cross-section, it tapers toward both the front and the back.

"Anhanguera was quadrupedal and didn't walk solely on its back feet," says Witmer. "It had long forelimbs, though, and so was canted into a more upright position than was the shorter-armed Rhamphorhynchus."

Its head hung at a downward slant, which, according to Witmer, likely enhanced its binocular vision and terrestrial agility.

"The major evidence for the down-turned head," he says, "comes from the orientation of the inner ear canals."

Those, however, remain deep within Anahanguera's rock head, visible only virtually.

To examine the skulls' chambers encased within the mineralized fossils, the researchers used non-invasive X-ray computerized axial tomography – more commonly known as "CAT scans." Custom-built to explore the internal structure of natural – and often fossilized – objects, the scanner at the UT facility has greater resolution and penetrating power than a conventional medical-diagnostic CAT scanner. It feeds its data to DigiMorph, an NSF-funded digital library that develops and makes available 2-D and 3-D structural visualizations of living and extinct animals, mostly vertebrates.

DigiMorph turned the scanners' deep and detailed views into digitized "virtual" endocasts, which revealed more differences between the vestibular networks in the two skulls. For example, the orientation of this "osseous labyrinth" relative to the long axis of the skulls varied. This is particularly noteworthy because of the semicircular canals. These fluid-filled chambers serve as levels to help the brain determine which way is up, arrange an appropriate rate of acceleration, and maintain equilibrium. (All vertebrates have them in their inner ears.)

In Rhamphorhynchus, the orientation of the canals suggests a level-headed approach to flying. In Anhanguera, it suggests a head turned strongly downward both in flight and when on the ground.

Both extinct pterosaurs had about twice the relative amount of labyrinth space than do living birds. (Birds, likewise, have enlarged labyrinths relative to mammals.)

The researchers also found in both animals another greatly enlarged neurological structure critical to flight. Called the flocculus, this lobe of the cerebellum has important connections with the vestibular apparatus, the eye muscles and neck muscles, which work together to stabilize and sharpen an image of prey upon the retina.

The flocculus may also connect to the membrane covering the wing, gathering massive amounts of sensory input on body orientation amidst aerodynamic forces. In both pterosaur subjects, the flocculi occupy about 7.5 percent of total brain mass; in birds, they occupy about 2 percent or less.

According to the Nature report, "Enhancement of such mechanisms seems reasonable in these two visually oriented pterosaurs given their apparent foraging style of aerial fish-eating."


Story Source:

The above story is based on materials provided by National Science Foundation. Note: Materials may be edited for content and length.


Cite This Page:

National Science Foundation. "Not All Aerial Reptiles Were Level-headed, CT Scans Show; Inside View Of Pterosaurs’ Brain Yields Insights To Posture, Behavior." ScienceDaily. ScienceDaily, 30 October 2003. <www.sciencedaily.com/releases/2003/10/031030062123.htm>.
National Science Foundation. (2003, October 30). Not All Aerial Reptiles Were Level-headed, CT Scans Show; Inside View Of Pterosaurs’ Brain Yields Insights To Posture, Behavior. ScienceDaily. Retrieved September 17, 2014 from www.sciencedaily.com/releases/2003/10/031030062123.htm
National Science Foundation. "Not All Aerial Reptiles Were Level-headed, CT Scans Show; Inside View Of Pterosaurs’ Brain Yields Insights To Posture, Behavior." ScienceDaily. www.sciencedaily.com/releases/2003/10/031030062123.htm (accessed September 17, 2014).

Share This



More Fossils & Ruins News

Wednesday, September 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Explore Shipwrecks Off Calif. Coast

Researchers Explore Shipwrecks Off Calif. Coast

AP (Sep. 16, 2014) — Federal researchers are exploring more than a dozen underwater sites where they believe ships sank in the treacherous waters west of San Francisco in the decades following the Gold Rush. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Museum Traces Fragments of Star-Spangled Banner

Museum Traces Fragments of Star-Spangled Banner

AP (Sep. 12, 2014) — As the Star-Spangled Banner celebrates its bicentennial, Smithsonian curators are still uncovering fragments of the original flag that inspired Francis Scott Key's poem. (Sept. 12) Video provided by AP
Powered by NewsLook.com
Spinosaurus Could Be First Semi-Aquatic Dinosaur

Spinosaurus Could Be First Semi-Aquatic Dinosaur

Newsy (Sep. 11, 2014) — New research has shown that the Spinosaurus, the largest carnivorous dinosaur, might have been just as well suited for life in the water as on land. Video provided by Newsy
Powered by NewsLook.com
Meet Spinosaurus, the First-Known Water Dinosaur

Meet Spinosaurus, the First-Known Water Dinosaur

AFP (Sep. 11, 2014) — Spinosaurus aegyptiacus was adapted for both land and water, and an exhibit featuring a life-sized model, based on new fossils unearthed in eastern Morocco, opens at the National Geographic Museum in Washington on Friday. Duration: 01:02 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