Tetraxylopteris
The Catskill Geologists; The Mountain Eagle; July 6, 2018
Robert and Johanna Titus
Tetra-what? Are we kidding? Well, if you have been able to read this far, we commend you. Our title is a one-word mouthful, isn’t it? But, here in the Catskills, this is something of an important word. It’s the genus name for a fossil plant that lived in Gilboa about 380 million years ago, during the late Devonian time period. With a name like Tetraxylopteris it’s going to be a challenge to write about this plant, but we are pros; let’s give it a try and even attempt to explain why this is something important in our region’s fossil record.
Take a look at our photo. It was taken in the open shed outside of the Gilboa Museum. The fossil lies upon the surface of an enormous boulder, collected in the Gilboa vicinity. Being outside, you can visit it any time you wish, all year round. The plant is a very distinctive one. You can see a main stem and then branches that stick out at nearly right angles. When those branches, themselves, have their own branches, those stick out–again at 90 degree angles. This rectangularity makes the plant so easy to identify. You just became an expert, but why is it important?
Tetraxylopteris takes us back to the Devonian time period when land plants had only recently evolved and were spreading out across the landscapes of the world. This was important evolution. We are speaking of the first time appearance of forest ecology itself–now that’s important.
The plant was a true land dweller; it had tissue that served to draw water out of the ground and pass it upwards into the stem and branches. We call that vascular tissue and it has always been an important feature of all true land plants. It had a woody stem and wood was a new “idea” for plants back then. Some of the very best preserved specimens have flattened structures on their outermost branches. These are thought to be proto-leaves, not true leaves but something broad, flat and photosynthetic. It was a good evolutionary start for real leaves.
It’s that woody stem that has been regarded as a trait that links it with the gymnosperms, many of which are today’s evergreens and cone-bearing trees. Tetraxylopteris was something you might call a bush; it probably did not grow as tall as a true tree. Some paleobotanists think it grew in thickets with each bush supporting its neighbors.
It was a primitive land plant in the manner of its reproduction. It did not produce seeds; it had an organ that produced tiny reproductive structures called spores. Individual spores are single cells that spore-producing plants use. They are caught up by wind and blown around, a lot like pollen. When they fall to ground they act like seeds and grow into a new plant. That may link this plant with ferns. Ferns, too, are primitive land plants that reproduce by using spores. If you think that the pollen season is bad nowadays, it might well have been much worse during the Devonian!
By the way, that name is not as hard to say as you might think. Try saying “tetra – xi – lopp – teris.” With a little practice it rolls off the tongue. And you will feel so smart just being able to say it!
The Gilboa Museum is having a big event, the Gilboa Fest, this Sunday, July 8th from 10:00 to 4:00. Why not come along and see their fossil plants, including Tetraxylopteris, at the same time?
Contact the authors at randjtitus@prodigy.net, Join their facebook page “The Catskill Geologist.”
