Seminars on Science
Diego Pol


Diego comes face to face with the skull of an extinct crocodilian in one of the Museum's exhibit halls.
Diego comes face to face with the
skull of an extinct crocodilian in
one of the Museum's exhibit halls. ©AMNH

Diego Pol was just 25 years old when he arrived at the American Museum of Natural History (AMNH) in September 1999 to work with Museum paleontologists while pursuing his Ph.D. at Columbia University. He was already a grizzled veteran of paleontological fieldwork, with nine fossil-gathering expeditions under his belt. From 1994 to 2005, he took at least one trip each year into the deserts of his native Argentina. One 1994-95 expedition lasted 60 days, and in 1996, he spent a total of 75 days in the field. To complement his 265 days of desert fieldwork, he also published eighteen scientific papers in paleontology journals and books, and became one of the world's leading experts on extinct crocodilians that were the subject of his undergraduate thesis. His Ph.D. dissertation was focused on the early evolution of Sauropodomorph dinosaurs, including the study of new fossils that lived in South America 200 million years ago.

Diego began studying paleontology while still in high school, when he signed up for an internship program at the Natural Science Museum of Argentina (NSMA) in Buenos Aires, and he continued working with the scientists there all through college. "The paleontologists always needed help," he says. "It was a good way to get the feel of the day-to-day routine in a lab, and I liked it a lot. I was already interested in paleontology, and these experiences strengthened my conviction to pursue my interests."

Diego's high school was affiliated with the University of Buenos Aires, Argentina's top university. Professors from the university taught at the school, whose students automatically enter the university after graduating. Close links between the university and the museum meant that students had the opportunity to participate in the curators' research while they pursued their studies. Diego served as a scientific assistant to a researcher studying the ancestors of modern crocodiles, which became the focus of his university thesis. He also helped prepare fossils for analysis and display, and made casts of dinosaur bones for museum exhibitions.

When making copies of dinosaur bones to show the public, Diego made molds out of silicone and then cast the bones in polyester. When preparing actual fossils, he would use an air scribe, which is like a tiny jackhammer, to chip away the rock attached to a fossil. "It usually separates easily from bone," Diego says, "but if you go too fast, you can press through the rock into bone, and break the bone." He still remembers a scratch he carved into a fossil with the air scribe. Most people do this at least once, he says.

After a year of assisting NSMA scientists, Diego was invited to go on his first fossil-gathering expedition. In September 1993, the group went to La Rioja Province in northwest Argentina, an area containing fossils from the late Triassic era (about 200 million years ago) where the previous year someone had found an extremely primitive species of turtle. They quickly found another nearby, and then two more people shouted "I found one!" It turned out there was a massive layer of more than 40 turtles, practically overlapping each other.

Diego managed to convince this camel's owner to let him take it for a spin when they met at a spring in the Gobi desert.
Diego managed to convince this camel's
owner to let him take it for a spin when
they met at a spring in the Gobi desert. ©AMNH

From then on, during school breaks and summer vacations he joined every expedition he could. The NSMA led frequent expeditions to La Rioja Province and to Patagonia in the south, the most important source of fossil discoveries in Argentina. The trips were true adventures. During these outings, which lasted up to two months, the crew camped in the desert, where temperatures frequently reached 100 degrees during the day. Since water was precious, they routinely had to go a month without a shower.

A bigger hardship was the constant sun. Despite the heat, Diego always wore long pants, both to block the sun and because in the desert, "almost every plant has spines." Hats helped, but he preferred not to use suntan lotion because when combined with blowing dust, the lotion caused a thick layer of mud to form on his skin. "It was pretty disgusting," he says.

If he worked in one place for a few days, digging up a large fossil, he would rig up a tarp for shade. But when he was walking around to search for fossils, there was no shade to be found. "If you are really lucky," he jokes, "on the first day you find a good and big dinosaur, and you can spend a month digging it up." But if the group was searching for small mammal fossils, even if Diego found 20 of them, the digging took so little time - a few minutes each - that he spent virtually all of his time prospecting in the hot sun.

Unless there was a town nearby, the crew packed all the food and water they would need for the entire expedition and brought it with them. They ate a lot of rice and other non-perishable items, such as noodles, potatoes, and canned tuna, peas, and corn. If they were near a village, they could occasionally buy a goat or a lamb. But according to Diego, Argentines are unwilling to go very long without beef - It's a beef-based culture," he says - so whenever someone had to go for water or gas, they would bring some beef back to camp and have a barbecue. Of course, without refrigeration, the meat would not look so good in following days. "A few times, the meat got somewhat green," he recalls. "Some parts were more green than others. But you didn't notice after it was cooked."

But the worst health hazard did not come from green meat. On a 1996 expedition to western Argentina, they were pleased to find a natural spring nearby. "The people near there said the water was good, so we were all drinking it. But couple of days later." He shakes his head with a grimace. "The local people were used to it. But I would say eight out of 10 of us got sick. After that, we boiled it."

One of Diego's best finds came on a 1997 expedition to northwest Argentina. The crew went to an area where it was common to find skull fragments of the "crocs" he was studying. Diego found a partially exposed skull and started digging. As he slowly and carefully unearthed the fossil, "I saw the whole skull.then the neck.then an arm.then the other arm.then two legs.then the tail." He grins, still amazed at his good fortune. The fossil turned out to be the first complete skeleton ever found of that species, which happened to be the exact species Diego was studying.

Diego pauses after breakfast before beginning a day of hunting middle Jurassic fossils in Patagonia, Argentina.
Diego pauses after breakfast before
beginning a day of hunting middle
Jurassic fossils in Patagonia, Argentina. ©AMNH

During his PhD studies Diego participated in four of the American Museum of Natural History's annual expeditions to Mongolia, invited by his advisor, Mark Norell, the AMNH's head of paleontology. It was a special thrill for Diego to see Ukhaa Tolgod, where Mark had found a fossilized dinosaur brooding a nest of eggs and other famous discoveries that Diego had read about in Argentina.

In his research at the AMNH, Diego continued his studies of ancient crocodilians. When a group of researchers from the State University of New York at Stony Brook found a croc fossil in Madagascar that was surprisingly similar to the ones Diego studied in Argentina, they invited him to collaborate. One of their conclusions was that the similarities between the crocs suggest that Madagascar and South America were linked during the Late Cretaceous era. The resulting paper was published in June 2000 in the prestigious journal Nature, quite a coup for a first-year grad student.

Diego is also studying some newly discovered theropod species with Mark that could be of immense importance because their skeletons show traits that had previously been observed only in birds. For instance, though they look like dromaeosaurs, they have avian tails. In dromaeosaurs, each tail bone has a long spur that extends over the next two vertebrae, which presumably helped the fast-running creatures hold their tails out straight for balance. The new fossils do not have these spurs, making their tails more flexible, like birds'. These fossils could provide another link in the evolution of birds from theropod dinosaurs.

In addition to analyzing fossilized crocs and theropods, Diego also writes about theoretical issues in paleontology. He has published three papers co-authored with Mark, on an improved way to use the known sequence of evolutionary history to speculate on gaps in the fossil record. Diego credits his theoretical research to being at the Museum, and particularly to working with Mark. "I'll have some ideas, and we'll go out after work and talk for a few hours," Diego says. "I'll do preliminary work, then show it to him, and he'll advise me how to continue. We'll get together again, I'll write a first draft, and he'll have lots of suggestions and corrections. It's the best way to work with an advisor."

Diego has also had fruitful collaborations with other Museum scientists. "I really feel like these years were a turning point in my education. So many great people have influenced me. Not only Mark, but other curators and scientists that work in cladistics," the Museum's approach to organizing species according to the evolution of shared derived traits. Says Diego, "The Museum environment is really exciting. A lot of really smart people are working really hard on a wide variety of problems, but within a common framework, cladistics. In a sense, we are all facing similar problems, whether we're working with the DNA of flies, leaches, spiders, or fossil dinosaurs. People talk, interact, and collaborate a lot. The interaction will give you a lot of insights."
Diego received his PhD in the Fall of 2004 and later spent a year at The Mathematical Biosciences Institute (The Ohio State University) doing a postdoctoral fellowship in theoretical aspects of cladistic analysis. In early 2006, Diego took a curator position in an Argentine Museum located in Patagonia. The Paleontological Museum E. Feruglio is located in a critical place, really close to fantastic outcrops rich in Jurassic and Cretaceous Dinosaurs.

 

 

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