Fuente: REALscience
Expuesto el: martes, 20 de marzo de 2012 2:23
Autor: Michael Bradbury
Asunto: Fossil Hunters Find Camels in Panama
| Paleontologists got a brief glimpse into Earth's tropical past when the U.S. built the Panama Canal Zone almost 100 years ago. But the scientific world didn't know what was there until the unearthed fossils housed at the Smithsonian were studied and Frank Whitmore and Robert Stewart published the first paper on Panamanian fossils at the end of the 1960s. At the time they determined that South America was a giant island continent with its own diverse and unusual animal life until the isthmus of Panama grew through uplifting of tectonic plates, connecting North and South America and cutting off the Atlantic Ocean from the Pacific.
With the Discovery of Ancient Camels 20 Million Years Ago, Tectonic History Needs Revision A few years ago the largest expansion of the Panama Canal began and the $5.2 billion project is giving scientists another glimpse of our tropical geological past. This time, a PhD candidate from the University of Florida unexpectedly found camel fossils while doing field excavations at the construction site in Panama. Aldo Rincon found the fossils of two species of small camel that roamed the area 23 million years ago, well before North and South America were joined together. Researchers from Panama, the U.S. and the Smithsonian Tropical Research Institute also report finding fossils of horses and marine vertebrates, including ancient marlins and turtles. Rincon says he was very excited when he took the fossil pieces back to his lab in Gainsville and began piecing them back together. He realized that he had a nearly complete camel jaw that had been nearly perfectly preserved beneath a greenish coating of volcanic ash. He says, "It's something like Pompeii."
University of Florida Geologist Aldo Rincon at Panama Canal Expansion Site, 2011 The 33-year-old researcher was most surprised by the camel's teeth. He says they are crocodilian and is still trying to figure out why. Other paleontologists who have been following the fossil find for a couple of years believe that modern camels have flat teeth because they eat grass. Ancient camels may have needed sharp teeth to cut into fruit and thick foliage found in the area. So far five camel fossils have been recovered from the Panama Canal expansion project. Four belong to the larger species, which looked little like a modern camel. Besides having no hump, they probably only stood about three feet tall. The discovery by Florida Museum of Natural History researchers extends the distribution of mammals to their southernmost point in the ancient tropics of Central America. The tropics are home to the world's most important ecosystems, including rain forests that regulate climate systems and serve as a vital source of food and medicine, yet little is known of their history because lush vegetation prevents paleontological excavations. Bruce MacFadden, vertebrate paleontology curator at the Florida museum and co-principal investigator on the National Science Foundation grant funding the project says, "We're discovering this fabulous new diversity of animals that lived in Central America that we didn't even know about before."
Lower Jaw of Aguascalietia Panamaensis, A New Species of Ancient Camel, Courtesy of University of Florida Jamarillo says scientists never expected to find a camel in the canal zone. He adds, "It's really, really a surprise." Part of the reason that it's such a surprise is that scientists thought they had pinpointed the date that North and South America joined together. But they may be wrong, given the discovery of these mammal fossils. Researchers have long thought the isthmus of Panama rose about 3.5 million years ago, but now that scientists have discovered a camel species living in the area so much earlier, that hypothesis is being questioned. Before Rincon and his team found the camel fossils in Panama, no one had spotted camels south of Mexico. The camel family likely originated in Florida and Texas about 30 million years ago and spread across most of North America and changed as they migrated south. A construction project near San Francisco unearthed some ancient camel bones a couple years ago that dated back 11 million years. The camels Josh Wyatt at PaleoResource found in the Caldecott Tunnel excavation were from giant camels that he says were probably the size of giraffes. Rincon made the Panamanian camel discovery over a two-year period but didn't publish until recently. The study appears in the March 2012 issue of the Journal of Vertebrate Paleontology. Since 2007, when the multi-year excavation project began, thousands of fossils have been recovered and sent to labs across the Americas for analysis. Until the expansion project is finished and the new canal channels opened paleontologists will follow the footprint of the construction, searching for lost moments in geologic time, trying to piece together the planet's past through the fossil record.
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