It may look like a big cactus, but Prototaxites is thought to have been an enormous prehistoric fungus that fed on the remains of the dead and decaying. It lived more than 350 million years ago! And at up to 29 feet tall (8.8 m), it towered over the earliest land plants, which measured only a foot or less in height.
Prototaxites seems to have been an important fuel source for some of the earliest known fires on the planet. As it burned and turned to charcoal, it helped lock down carbon in the soil. Indirectly, such events helped raise the atmosphere's oxygen levels, which would have aided in the evolution of land animals.
The Field Museum holds part of the type specimen—the official scientific sample—of Prototaxites southworthii. In order to identify another fossil as this species, it must be compared with the Museum's specimen.
Scientists at The Field Museum are studying Prototaxites to learn more about the role that large-scale fires play in altering the atmosphere and changing weather patterns.