In northern Thailand, fossil trees nearly matching the heights of today’s tallest redwoods have been discovered. The longest petrified log measures 72.2 meters (237 feet), suggesting that the original tree reached more than 100 meters (330 feet) in height in a wet tropical forest around 800,000 years ago.

These trees appear closely related to the species Koompassia elegans, part of the same family as beans, peas, and black locust trees, explained study lead author Marc Philippe from France’s University of Lyon. This indicates that the ancient trees are not related to today’s tallest trees, such as Australia’s Eucalyptus (gum trees) and California’s Sequoia (redwoods), both of which can grow up to 130 meters (425 feet).

Interestingly, no trees in present-day Thailand approach the size of these ancient giants.















The largest unbroken petrified tree trunk in the world (right). The reconstructed tree with a modern giraffe beside it for scale. (Image credit: courtesy of Marc Philippe, Université de Lyon)


“The tallest trees currently in Thailand are nearly 60 meters (200 feet),” Philippe wrote in response to an email inquiry about his new paper in the April issue of the journal Quaternary Science Reviews. “To my knowledge, the tallest tree recorded in Thailand is a Krabak tree from the Dipterocarpaceae family (‘tropical oaks’), standing 58 meters (190 feet) tall.”

The sediments housing the fossil trees suggest they grew in a wet forest on the edge of a lowland plain. Today, these fossil trees lie at an elevation of 170 meters (550 feet) above sea level, where the climate alternates between wet and dry seasons, known as monsoonal. Philippe suggests that the region might have experienced some uplift since the trees fell.

The story of how these buried trees were found is fascinating. A small section of a large petrified log was discovered ten years ago by a villager in a reserve forest in Ban Tak District, Tak Province. The discovery was reported to officials from the National Park, Wildlife, and Plant Conservation Department. An official came to examine the log and surveyed the area. The log was excavated to a length of 21 meters (70 feet) without reaching the end. Ground-penetrating radar revealed that 30 meters (100 feet) of the trunk remained unexposed. In 2005, funds were secured to excavate the entire trunk. Currently, seven of nine discovered petrified trunks have been excavated, mostly in 2005.

“The result was the uncovering of what is considered the world’s longest piece of petrified wood, measuring 72.22 meters (236.9 feet),” the researchers report. “In 2006, the park’s name was changed to Petrified Forest Park due to these fascinating discoveries.”

The presence of large trees in the past that are unrelated to today’s giant trees exemplifies convergent evolution, where similar environmental factors result in similar traits in unrelated species. For example, rheas (South America), ostriches (Africa), and emus (Australia) are all large, unrelated flightless birds that evolved on different continents. The drive for trees to grow taller likely involves a dense forest and competition for sunlight. Over hundreds of millions of years, many very tall tree species have likely existed, probably from every plant family. However, finding an entire petrified trunk to confirm this is extremely rare.


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