PROVIDENCE, R.I. [Brown University] Aggregating nearly the entire landmass of Earth, Pangaea was a continent the likes our planet has not seen for the last 200 million years. Its size meant there was a lot of space for animals to roam, for there were few geographical barriers, such as mountains or ice caps, to contain them.
Yet, strangely, animals confined themselves. Studying a transect of Pangaea stretching from about three degrees south to 26 degrees north (a long swath in the center of the continent covering tropical and semiarid temperate zones), a team of scientists led by Jessica Whiteside at Brown University has determined that reptiles, represented by a species called procolophonids, lived in one area, while mammals, represented by a precursor species called traversodont cynodonts, lived in another. Though similar in many ways, their paths evidently did not cross.
"We're answering a question that goes back to Darwin's time," said Whiteside, assistant professor of geological sciences at Brown, who studies ancient climates. "What controls where organisms live? The two main constraints are geography and climate."
Turning to climate, the frequency of rainfall along lines of latitude directly influenced where animals lived, the scientists write in a paper published this week in the online early edition of the Proceedings of the National Academy of Sciences. In the tropical zone where the mammal-relative traversodont cynodonts lived, monsoon-like rains fell twice a year. But farther north on Pangaea, in the temperate regions where the procolophonids predominated, major rains occurred only once a year. It was the difference in the precipitation, the researchers conclude, that sorted the mammals' range from that of the reptiles.
The scientists focused on an important physiological difference between the two: how they excrete. Mammals lose water when they excrete and need to replenish what they lose. Reptiles (and
'/>"/>
| Contact: Richard Lewis Richard_Lewis@brown.edu 401-863-3766 Brown University Source:Eurekalert |
Related biology news :
1. Evidence is weak for tropical rainforest 65 million years ago in Africas low-latitudes
2. Better food makes high-latitude animals bigger
3. Iron and biological production in the high-latitude North Atlantic
4. Earths biodiversity: What do we know and where are we headed?
5. Water, water, everywhere… but is it safe to drink?
6. Where did flowers come from?
7. Water, water everywhere focus of new sustainability project
8. Where unconscious memories form
9. Where did you get those eyes and that brain?
10. Tuning into cell signals that tell where sensory organs will form inside the ear
11. Where do the drugs go?
 |
| Copyright © 2003-2012 Bio-Medicine. All rights reserved. ABOUT | CONTACT US | DISCLAIMER | PRIVACY POLICY | TERMS AND CONDITIONS |  |