Forest Primeval: The oldest known trees finally gain a crown

For more than a century, the world’s earliest known trees were represented only by preserved stumps. Now, fossils recently unearthed in upstate New York reveal the tops of those trees.

In the early 1870s, paleontologists discovered fossilized stumps in a riverbed near Gilboa, N.Y. In the 1920s, quarrymen excavated dozens more nearby. Those 0.5-to-1.5-meter relics, preserved upright in rocks about 385 million years old, are considered to be the remains of Earth’s oldest forest, says William E. Stein, a paleobotanist at Binghamton (N.Y.) University.

Distinguishing features of the species, dubbed Eospermatopteris eriana, include a series of fibrous strands running up and down the tree trunk. Those strands probably transported water to the upper reaches of the tree and strengthened the trunk, says Stein.

Paleontologists in 2005 discovered two fossils of upper parts of an Eospermatopteris tree at a site about 13 kilometers east of Gilboa. Surprisingly, the new fossils indicate that the tree’s top belongs to Wattieza, a genus of plant previously known solely from the branches that it shed.

Because only small fragments of Wattieza plants had been found before, “we never knew how big these plants were or what they looked like,” says Christopher M. Berry, a paleobotanist at Cardiff University in Wales. He, Stein, and their colleagues describe their new finds in the April 19 Nature.

One of the new fossils is a 6-m-long section of trunk, which tapers from a diameter of 47 centimeters at one end to 13 cm at the other. The thick end of the log shows the fibrous strands characteristic of Eospermatopteris stumps, says Stein. The other end, presumably near the top of the ancient tree, is covered with scars left where branches had died and fallen off.

The other fossil is much shorter but contains the critical evidence that links Eospermatopteris to Wattieza, says Stein. The thicker end of this log bears scars where branches had once grown, but the crown of the plant retains branches that were alive when the tree fell. Each branch was about 1 m long and 6 cm across at its base, says Stein. Instead of having leaves, the branch just divided as it grew, and then divided again and again. The end of a mature branch looked like a bottle brush.

The team estimates that the fossils represent trees about 8 m tall. Some of the stumps found at Gilboa had about twice the diameter of the new specimens, so the trees there were probably much taller, says Stein.

The scientists presume that each branch contained chlorophyll. But because they lacked leaves, the ancient trees’ branches probably weren’t efficient at collecting light, says Brigitte Meyer-Berthaud, a paleobotanist at the French National Center for Scientific Research in Montpellier.

Nevertheless, these trees—”probably the biggest on Earth at the time,” Meyer-Berthaud notes—succeeded because their height enabled them to spread spores more effectively than their competition did.