THE OFFICIAL DINO LAND WEBSITE STATE FOSSILS

The modern day state of Arizona is nothing more than a vast stretch of dry, arid land. But, 225 million years ago, during the Late Triassic, the climate and topography was much different. During this time all of the continents were gathered into a single landmass known as Pangaea, with the land that now composes Arizona lying as a stretch of tropical turf in the northwest corner of the supercontinent. This stretch of tropical land was furthermore composed of a lowland basin, bounded to the north and west by a receding sea, and to the south with a chain of mountains. Within this basin existed a rich and diverse ecosystem of plant and animal life. Unlike the climate of modern day Arizona, this land was likely warm and wet with seasonal periods of aridity.

One rainy season, more than 200 million years ago, an enormous volcano, driven by the gradual breakup of the supercontinent, opened through a fissure in this basin. It proceeded to erupt, overloading the basin with ash and debris. Rivers ran over their banks, and floodwater toppled the forests. The ash proceeded to cover many of these trees, burying them at least 30-40 feet under the surface. Shut off from air and bacteria, the trees were gradually replaced by rock-hard minerals, which began to crystallize. Millions of years later, these crystals remain as vividly colored fossils.

Today these fossilized trees are found in the 93,492-acre Petrified Forest National Park, a federally controlled region in the Painted Desert, east of Holbrook and south of Interstate 40. During the 150 years in which this area has been known to science, countless species of plants and animals have been discovered and named. The most abundant of any of these species, making up 90 percent of all of the petrified wood in the park, is Arizona's state fossil, the conifer Araucarioxylon arizonicum. Araucarioxylon was a member of the Family Araucariaceae, better known as the araucarians. In life this large tree grew in the upwards of 150-200 feet high, and had a trunk diameter of 4-5 feet. Studies show that many of these trees may have even grown together in large stands, providing a thick canopy cover to the basin. Today, the araucarians survive, with such rare and strange species as South America's monkey-puzzle tree and the famous Norfolk Island Pine.

The first fossils of Araucarioxylon were undoubtably discovered by Native Americans, many of which concocted elaborate stories to explain their existence. For example, the Piutes believed the petrified logs were spent arrow shafts sent by their thunder god, Shinauav. Other tribes even built dwellings out of the logs, and many used the hard petrified wood for arrowheads. Decades later, in 1878, Civil War General William Tecumseh Sherman spotted "extraordinary specimens of petrification" while traveling in the new Arizona Territory. As a regent of the new Smithsonian Institution, Sherman wrote to his cohort, Col. Peter Swaine, telling him to collect some interesting samples for the museum. One year later, Swaine dispatched Lieut. J.F.C. Hegewald, 12 men, and two mule wagons to collect two large samples. Today these samples stand in the Smithsonian. But, Sherman's specimens opened up the way for commercial collecting, and in 1899 a U.S. Geological Survey declared something had to be done to protect the land. Seven years later President Theodore Roosevelt made the area a national monument. Nearly 60 years later, in 1962, President Kennedy finally designated forest a National Park. Lucky for this ancient forest, it was saved.

FOOTNOTE: All text is taken directly from the magazine Fossil News: The Journal of Avocational Paleontology, January, 2001.

© 2000 brusatte@theramp.net