GeologyPage has a story about why large dinosaurs were somewhat rare in the tropics. There were small bodied meat-eaters, but the absence of large plant-eaters in the low-latitudes is one of the great, unanswered questions about the reign of the dinosaurs.
There may now be an answer. Researchers from various institutions worked to create a detailed picture of the climate and ecology of 200 million years ago from the rocks and fossils of the Ghost Ranch in northern New Mexico. This Late Triassic site was near the equator at that time.
The new findings show that the tropical climate swung wildly with extremes of drought and intense heat. Wildfires swept the landscape during arid regimes and continually reshaped the vegetation available for plant-eating animals.
"Our data suggest it was not a fun place," says study co-author Randall Irmis, curator of paleontology at the Natural History Museum of Utah and assistant professor at the University of Utah. "It was a time of climate extremes that went back and forth unpredictably and large, warm-blooded dinosaurian herbivores weren't able to exist nearer to the equator -- there was not enough dependable plant food."
The study, led by geochemist Jessica Whiteside, lecturer at the University of Southampton, is the first to provide a detailed look at the climate and ecology during the emergence of the dinosaurs. The results are important, also, for understanding human-caused climate change. Atmospheric carbon dioxide levels during the Late Triassic were four to six times current levels. "If we continue along our present course, similar conditions in a high-CO2 world may develop, and suppress low-latitude ecosystems," Irmis says.
The other authors are Sofie Lindström, Ian Glasspool, Morgan Schaller, Maria Dunlavey, Sterling Nesbitt, Nathan Smith and Alan Turner.
