Prairie Quillwort is 50 centimeters tall (© 2015 Robbin Moran); Scale Tree is 50 meters tall (source). Both are lycophytes—formerly "Fern Allies".

This episode of The Monthly Fern was going to feature Isoetes melanopoda, the Prairie Quillwort, mentioned last month in the wildly popular Prairie Spikemoss post (1). But in my search for information I fell down a rabbit hole and landed with a splash in an ancient Wonderland—a wet lush forest 350 million years ago near the start of the Carboniferous Period (2). After extricating myself from the muck I looked around. Tree ferns, horsetails and dragonflies looked familiar, though a bit large. But the trees were very strange.

It was during the Carboniferous that wetland forests with tall trees first appeared in the fossil record. These were hot humid riotous tangles of vegetation growing in shallow water and muddy peat that reeked of decay. Dense stands of curious trees rose high above the understory. The most common (or best preserved) was Lepidodendron, the Scale Tree. "Scale" refers to the distinctive bark—a network of diamond-shaped leaf scars (Halliday 2022).

Wetland forest of the Carboniferous; large Lepidodendron on left (Meyers Konversationslexikon 1885–1890).

Though they've been gone for 300 million years, we know a lot about these trees. Their fossilized remains are among the most extensive for any plant from any geological period, and for good reason. Not only was Lepidodendron large and ecologically dominant, it lived in waterlogged conditions conducive to preservation. Paleontologists have been able to describe features ranging from spores to leaves to trees, and even stands of trees (Hetherington et al. 2016).

Lepidodendron differed in many ways from the trees we know. Stems of young trees were covered in long ascending needle-like leaves. These fell off as the tree grew taller and wider, leaving a spiraling network of diamond-shaped scars on the trunk. With age the trunk developed a thick tough outer layer—bark of sorts—but underneath was soft spongy tissue instead of wood. At maturity the stem branched dichotomously (repeatedly forked), forming a high crown as much as 50 meters above the ground. The final branchlets were tipped with strobili (cones) filled with spores, to be dispersed by wind (source). This so-called "tree" was an arborescent lycophyte, a fern relative.

Juvenile and mature Lepidodendron on left; trees to right are related lycophytes. Reconstruction from fossils, by Falconaumanni.

Given Lepidodendron's massive build, its lack of internal wood and the waterlogged habitat, it seems it would fall before reaching such heights. What kept it upright? Some credit the thick tough bark. But others argue convincingly for the robust root system. From very long rhizomes grew a profusion of highly-branched rootlets covered in root hairs—on the order of 26,000 rootlets per meter of rhizome! They intertwined with those of adjacent trees, forming a strong anchoring network—"trees holding onto one another for stability" (Hetherington et al. 2016; Halliday 2022).

Lepidodendron truly was an arboreal superstar, dominating the wetland forests and producing immense amounts of biomass for tens of millions of years (3). But it was doomed. By 300 million years ago, the Carboniferous rainforests and arborescent lycophytes were gone, destroyed by widespread drought. Lepidodendron's only surviving relatives are little herbaceous plants—Isoetes, the quillworts.

Bolander's Quillworts in a lake in the Wasatch Mountains, Utah. Andrey Zharkikh photo.

Now we return to the present—to a roadside waterhole along highway #44 in Mellette County, South Dakota, where W. H. Over (4) made his 15,878-th plant collection on July 10, 1924. Isoetes has not been collected in the state since.

Over correctly identified his collection to genus—Isoetes. Four months later, TC Palmer called it I. melanopoda, and Daniel F. Brunton agreed in 1995. The specimen resides at the Academy of Natural Sciences, where it has been digitized for all to enjoy (cropped here).

Like all quillworts, the Prairie Quillwort has no stem. Instead a cluster of leaves develops from the rhizome. From a distance these look like clumps of grass, but up close the leaves are distinctive—long, slender, quill-like, and bright green. The leaf bases are broad and pale, forming a swollen rootstock. These usually become black with age, hence the alternative common name—Black-foot Quillwort (plants with leaf bases that remain pale have been called I. melanopoda f. pallida).

Isoetes melanopoda; MWI photo.

Being a lycophyte, Prairie Quillwort produces no seeds. Nor does it have rows of spore-bearing sori on the undersides of its leaves as do most true ferns. Instead, spores are produced in a sac on the inner side of leaf bases.

Isoetes melanopoda; MWI photo.

Surely some readers are wondering ... how is little Isoetes like immense Lepidodendron? Why do botanists think they're related? Answer: It's the roots, especially the way they branch.

"this architecture is conserved among [Lepidodendron's] only extant relatives, herbaceous plants in the Isoetes genus. Therefore, despite the difference in stature and the time that has elapsed, we conclude that both ... have the same rootlet system architecture." (Hetherington et al. 2016)

Lepidodendron and Isoetes rootlets branch dichotomously, narrowing in a stepwise manner. A is a diagram of a rootlet with 4 levels of branching. B and C show rootlets of Isoetes and Lepidodendron (scale bars are 5 mm). Hetherington et al. 2015, Fig. 1 in part.

A final question: Is Prairie Quillwort gone from South Dakota? Has it suffered its own extinction? Maybe so. Skilled botanists have searched for it with no luck. But perhaps they were limiting themselves, looking only in "roadside waterholes" and such. Of great interest to me is its occurrence nearby in Minnesota where it's a state Endangered species. It's distribution there is quite limited—rainwater and seepage pools in quartzite rock outcrops, in the southwest corner of the state.

MWI photo.

This rock—Sioux quartzite—also crops out in the southeast corner of South Dakota. I visited several locations a few years ago, and am tempted to go back now that I have a such a vivid search image for Prairie Quillwort in my head!

Sign at Palisades State Park, SD. Pink marks exposures of Sioux Quartzite in southwest MN and southeast SD.

See any habitat?

Notes

Eerie eye of a hungry mosasaur!

Red X marks Kansas (USGS).

Coccolithophores thrived in the Kansas sea. Their microscopic scales formed chalk beds 600 feet thick! (source).

Collecting a Xiphactinus fossil (large fish) from the Kansas chalk, early 20th century (Fick Museum, Oakley).

Originally, a fossil was simply something “obtained by digging” (from L. fossilis). But in the 18th century, usage became restricted to preserved remains of living organisms (including impressions, and traces such as burrows and tracks). Fossils are common in the Smoky Hill Chalk, and often spectacular. Not surprisingly, when word got out that there was a treasure trove of novel fossils awaiting discovery in western Kansas, the big names in North American paleontology got really excited.

Marsh with his students, ready for adventure! (source)

“I put my soul into the letter I wrote him, for this was my last chance. I told him of my love for science, and of my earnest longing to enter the chalk of western Kansas and make a collection of its wonderful fossils, no matter what it might cost me in discomfort and danger.”

Sternberg explained that he was too poor to finance a trip himself, and asked for $300 for a wagon, horses, camping gear, a cook and driver. He sent no recommendations “from well-known men” but did mention his earlier work collecting fossil leaves in central Kansas. Cope quickly replied, sending a draft for three hundred dollars and a note: “I like the style of your letter. Enclose draft. Go to work.”

What are the chances today that a preeminent scientist would send funding to some unknown local?! Those were different times, it’s true, but there’s another likely factor—Cope’s bitter rivalry with Marsh (4). Cope surely was eager to get his hands on fossils from the Kansas chalk. As it would turn out, that $300 was a wise investment.

Charles H. Sternberg spent four hard but happy and productive years collecting fossils for Cope, the beginning of a fossil-collecting dynasty that included Charles and his three sons—George F., Charles M. and Levi. The Sternberg family often named children after relatives, so the full story can be hard to follow. But for this post, we only need to know Charles H. and his oldest son, George F. The latter was named after his uncle, George M., an army surgeon stationed in Kansas (and later US Surgeon General) who convinced his father to move the family there to farm.

By age 17, Charles H. Sternberg (1850-1943) knew he would devote his life to fossil-collecting. His father thought it a poor choice (source).

George F. Sternberg (1883-1969) collected his first important fossil, a novel plesiosaur, at age nine. His contributions to Kansas paleontology were monumental (Fick Museum, Oakley).

George F. Sternberg (source).

At 14 feet in length, this is a rather average Xiphactinus.

George F.’s Fish-Within-A-Fish advertises the Lithic Bookstore and Gallery in Fruita, Colorado.

Note the massive crest atop Pteranodon’s head and framed on the left (museum logo added).

Shark vertebrae.

Gillicus—Xiphactinus’s last supper—also was a predatory fish.

Seymouria is much older than the chalk, but was too photogenic to ignore. An amphibian with reptilian features, it lived roughly 275 million years ago. This one is about two feet long.

A reptilian tank with armored plates.

Niobrarasaurus was named for the Niobrara Formation, of which the Smoky Hill Chalk is a member. The creature was “built like a tank” and covered in armored plates, which may have helped maintain the bloat. This fossil was excavated from the chalk in 1930, and shipped off to the University of Missouri in Columbus. Seventy-two years later, Niobrarasaurus was repatriated, and is now on display at the Sternberg Museum.

Not Cretaceous, but I couldn’t pass it by!

Oh my! Hadrosaur ahead!!

… my expectations were wrong! This is a life-size realistic total-immersion diorama. Pterosaurs flew overhead, specifically Pteranodon sternbergii, named for George F., who collected the first specimen in 1966. Life-size sculpted creatures mingled with more of their kind in the panoramas on the walls behind.

Yikes! Xiphactinus!!

Paleontologists at work.

Knightia alta, a bit over 2 inches long; NPS photo.

Knightia slab, University of Wyoming Geology Museum.

“About two miles west of Rock Springs Station there is an excavation on the railroad which has been called the Petrified Fish Cut, on account of the thousands of beautiful and perfect fossil-fishes which are found on the surface of the thin shales, sometimes a dozen or more on an area of a square foot.” [Leidy 1873; italics added]

Leidy identified the fish as Clupea, the genus that includes today’s herring, and described two new fossil species.

Leidy’s Clupea humilis and C. alta; Figures 1 and 2, Plate XVII, Leidy 1873.

Clupea eocaena Jordan; NPS photo.

State Geologist and university professor Wilbur C. Knight (photo in UW Geology Museum).

Southwest Wyoming in the Eocene (Chicago Field Museum).

“In the valley of the latter [Green River] remarkable sections of strata are exposed to view. The group he [Hayden] calls the Green River shales, because the strata are composed of thin layers, varying in thickness from that of a knife-blade to several inches. The rocks all have a grayish-buff color on exposure, sometimes with bands of dark brown. These darker bands are saturated with a bituminous matter which renders them combustible.” (Leidy 1873)

Edge-wise view of Green River shale. Dark hydrocarbon-rich bands give the rock a noticeably oily smell. The little oval structure is fossilized fish poop.

Millions of Knightia fossils have been collected—and continue to be. It’s the most commonly excavated fossil fish in the world! You would think all Wyoming citizens would be proud of a fish with that kind of significance, especially one named for a Founding Father of Wyoming geology. But in 1986 when Mr. Miller's class approached the legislature about designation, they got nowhere.

The next year, things looked more promising. A bill was introduced. But an amendment was proposed almost immediately ... to designate the rattlesnake instead. Yikes! Miller and his students were stunned, their hopes sank. Fortunately the amendment was killed. Then another surprise—the bill passed unanimously, with full bipartisan support. Turns out the amendment was a fake, intended as a lesson in the legislative process.

Governor Sullivan signs the Fossil Fish bill under the watchful eyes of Anderson elementary school students.

Aspiring paleontologists learn the tricks of the trade.

Fossils from the Green River Formation, available for rubbings.

The festival was held in the Berry Center, University of Wyoming, Laramie.