#seed fern

[transparentfossil]

6.3" Fossil Seed Fern (Alethopteris) Plate - Pennsylvania

[geologyin-blog]

Amazing Neuropteris (seed fern) Fossil with Exceptional Preservation From Grundy County, Illinois. Age: Pennsylvanian (~300 m.y.a.).

Photo 📷 juarezfossil/IG

[harpagornis]

The Fern Prarie: fact or myth?

Moschorhinus and Lystrosaurus by DiBgd. Notably, the small plants in this picture are not true ferns but the extinct seed fern Dicrodium. To help illustrate my point.

In paleoart, “fern praries” are a type of biome frequently depicted. After all, if there was no grass in the Mesozoic (until the very end, at least), what else carpetted the ground?

A lot, actually. Seed-ferns, horsetails, moss…

The idea that ferns specifically formed the Jurassic savannas is not without merit. Modern ferns are the most common carpetting plants after grass, dominating forest undergrowth and even forming small plains in clearings. Some species can live in desert environments, so even places with little moisture could hypothetically boast seasonal fern steppes.

But the thing is, why ferns when there were so many other plant groups that could fill the grass niche? Notably, seed-ferns and small gymnosperms would be equally if not more fitting in more arid conditions. Perhaps some areas were carpetted by herb-like early angiosperms, not quite grass but almost there.

Remember that most fossil assemblages are biased towards riparian environments, where ferns surely excell. But there is little evidence for small flora in drier pre-Cenozoic environments, and as such the fern prairie must be questioned as an environment. It most likely existed, but I doubt it dominated the Mesozoic open spaces.

[flowerishness]

Fossils (part 2)

As I mentioned in my last post, the winter months are the doldrums for flower photographers and so I’m filling in with my plant fossil collection. The Bic lighters have been included to give a sense of scale and to add a bit of color. People looking for flowers will be pleased to note that my crocuses are putting up quite a show this morning, so we will return to our regular programming tomorrow.

a) My only Australian fossil. These leaves are the grand daddy of those gumtrees you see everywhere ‘Down Under’.

b) I call this seed fern trace fossil ‘The Silver Fern’ for obvious reasons.

c) This is the root of a giant horsetail (the black dots are where the rootlets were attached). This is from a time in the Paleozoic when horsetails were a hundred feet tall (30 meters), not just a couple of feet like modern scouring rushes.

d) Our friend Gareth was a real botanist and he once told me that this lineage of fern has been extinct since the Devonian period (400 million years ago).

[transparentfossil]

9.1" Fossil Seed Fern (Alethopteris) Plate - Pennsylvania

[shoplarkabout]

[fossilroulette]

Name: Neuropteris ovata Location: Texas, USA, Markley Formation Age: 307-315 million years ago, Carboniferous-Permian Periods

About 307-315 million years ago, the swamp forests where Neuropteris lived were disappearing. To help figure out why, scientists put fossilized leaves of Neuropteris, like the one in the photograph, under a microscope.

Scientists reasoned that the amount of carbon dioxide in the atmosphere might be related to the disappearing forests. Atmospheric carbon dioxide affects climate, and swamp forests can only occur under certain climate conditions.

Scientists used leaf pores, called stomata, to track changing amounts of carbon dioxide. Stomata let in carbon dioxide, which plants need to live. The more stomata per leaf, the less carbon dioxide in the atmosphere. If climate changed 306-311 million years ago, leaves of Neuropteris from different parts of that interval should have different stomata densities.

Stomata are small, about 30 times smaller than the width of a human hair. In order to see them, scientists had to prepare fossilized leaves for the microscope. They washed the fossils in acid and other strong chemicals to separate fossils from rock, then put the fossils on a glass slide. Then, they counted.

Scientists studied multiple fossilized leaves of Neuropteris ovata from different time points between 306 and 311 million years. In that time, stomata density dropped, matching an increase in carbon dioxide. Results from the leaves supported the link between the survival of swamp forests and carbon dioxide.

Specimen Number: UT 1185TX42

References: Cleal, Christopher J., Robert M. James, and Erwin L. Zodrow. "Variation in stomatal density in the Late Carboniferous gymnosperm frond Neuropteris ovata." PALAIOS 14(1999):180-185.

Where are similar fossils found?

[fatchance]

Fossil Series: Seed fern.