Earthwatch Expedition, Mexican Megafauna
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Ed Note: Senior volunteer Warren Strotroen shares his Earthwatch experience as a volunteer abroad in Mexico.
By Warren Stortroen
This was my second Earthwatch expedition with Oscar, paleontologist and Principal Investigator, from Universidad Natcional Autonoma de Mexico. I first joined him on FOSSILS OF THE SIERRA MADRE at Tecolatlan, southwest of Guadalajara, in 2005, where I learned to recognize the fossil bones of mammals that lived 1.5 to 5 million years ago during the Great American Interchange when the Panama land bridge opened.
For this project we were just outside of San Miguel de Allende in the mountainous old silver district of central Mexico, at the Hotel Parador El Cortijo - quite luxurious accommodations since they had both cool and hot swimming pools - the hot pool fed by natural springs! Breakfast was continental, and excellent dinners were served family style. Oscar and his wife, Hilda (also the recorder for all finds), brought lunch to the field - usually tortillas and one or two Mexican hot dishes. One day he did a special Mexican grill over a mesquite fire.
In addition to Oscar and Hilda our group included his assistant, Gerardo, and 8 volunteers - an older couple and myself were retirees and the rest still actively working. One guy was from Australia. We had training sessions or short lectures each morning before starting field work in the ancient lake bed north of town that was mostly soft sedimentary rock cut by deep arroyos where the bone becomes exposed.
The first two days were spent excavating where bone was plentiful and new volunteers could learn to recognize it We used ice picks and whisk brooms for most of the excavation and geologist's hammers for the tougher areas. We looked for teeth and jaws or bones with an articulation so they could be identified. These were mostly from several early species of horse, mastodon, camel, rhino and others. The best specimens were jacketed in plaster for later study and classification in the lab.
The third day we moved to a new area where I made an important and spectacular find! We were prospecting in a maze of rugged arroyos, and I had my own GPS, so made a home base and was able to leave the group and wander freely. At a promising arroyo branch I noticed a piece of mastodon tusk and a little further on spotted a ledge with some bone that appeared to be a joint socket or vertabrae and possible skutes. I selected some and brought them out to the van where we were to meet for lunch. When I showed them to Oscar he was elated! The tusk was only of minor interest, but the other bones were from a Glyptodon, an ancient relative of the armadillo but the size of a Volkswagon beetle!
Oscar asked if I could find the spot again, and I had marked it on the GPS, so after lunch we all trooped back and when I showed him the spot he looked up in the bank of the arroyo and said "Warren! I see the animal!" He could see a large section of the edge of the carapace! We went to the city of Dolores Hidalgo later that afternoon for pottery shopping, but spent the next two days excavating the animal.The final cast was so heavy we had to leave it for later removal by heavy equipment. Later, at the lab they found that the top of the carapace was missing, but we had collected a lot the missing skutes, part of the skull, nine teeth, some ribs and a leg bone. It appears that this may be the oldest and most complete specimen found in North America
Needless to say, this was one of my most exciting expeditions and I returned for three more teams! We had some very nice finds on those, but none as exciting as the Glyptodon!
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