Field of Science

Oldest tree on Earth - period!

Just days after posting about the oldest living tree on Earth, while working on educating myself about fern phylogeny, up pops references to the oldest tree on Earth, an organism that produced the first forests.

For those of you who really want to know, the tree in question is a pseudosporochnalean cladoxylopsid, a Devonian ancestor of ferns. This particular forest tree dates to 385 mya (million years ago), surpassing what was previously the oldest known tree, a progymnosperm called Archaeopteris, but a relative youngster appearing no more than 370 mya. Interestingly enough, both were discovered near Gilboa, New York in the Catskills. You may wonder how such big things as trees can escape the attention of geologists and paleobotanists, but it wasn't that these trees weren't known. They were, but the problem with fossils is that some assembly is required, if you know you have the right pieces to the puzzle.

The trunks of these forests were very well known. What wasn't know was what kind of tree they were. About 50 years ago a tree trunk with gymnospermous wood was found physically attached to a ferny foliage, the absolute evidence that these two fossils were in fact one and the same plant. And that is how progymnosperms, the ancestors of seed plants, were discovered.

Similarly the fossil trunks (Eospermatopteris) were matched up recently to smaller trunks bearing the fossil "foliage" called Wattieza. The entire tree is known by the latter name because was the first published (a principle of priority). The "foliage" is not composed of leaves, but of branches that were attached to the trunk in a helical whorl quite like the leaves of tree ferns, cycads, or palms. And now that it was known how big the trunk was, their height could be estimated, and these ancient trees grew to 8 meters. This is quite amazing because at the beginning of the Devonian (416 mya), land vegetation was no taller than knee high. And just 30 million years later, there were forests.

Forests really change things because trees are giant obstacles that alter their environment, the weather, the climate, the soil, and they make habitat for other organisms. So trees like this are responsible for transforming a barren terrestrial environment into a green Earth we would recognize. But it is hard at such a great distance to appreciate such organisms, and to that end I can think of no more fitting appreciation than a poem.

Ode to a pseudosporochnalean cladoxylopsid

I think that I shall never see
A poem lovely as a pseudosporochnalean cladoxylopsid . . . tree

A tree whose “whorled dichotomous ultimate units” . . . earn
An ancestry to the modern fern

A tree whose “photosynthetic/reproductive modules” . . . on high
Provide lowly detritivores with a food supply

A tree whose “digitally branched modules” . . . rain
Spores upon a Devonian plain.

A pseudosporochnalean cladoxylopsid that in times, post Ice Age
Is resurrected by a geology hammer’s rage

Poems are made by fools like me
But only Darwin can theorize a pseudosporochnalean cladoxylopsid . . . tree

By Robert Titus, Kaatskill Life, Winter 2007-2008.

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