A Fossil Fish Festival!

Paleontologists at work.

Thirty-one years ago, a small group of Wyoming citizens launched a campaign to honor a fish, specifically a small uncharismatic herring-like fish that hadn’t been seen for 50 million years. They didn’t get very far. The legislature had no interest in small fish nor the distant past. But these advocates were driven by a passion far exceeding that of most lobbyists—perhaps a passion of innocence, for none were older than twelve.

The next year, they tried again … and this time they succeeded! Knightia was designated State Fossil of Wyoming.

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

Knightia slab, University of Wyoming Geology Museum.

When these exquisitely-preserved fish fossils began to surface by the thousands, they impressed even the most experienced of experts. Paleontologist Joseph Leidy of the University of Pennsylvania examined fossils sent by geologist Ferdinand Vandeveer Hayden, head of the US Geological Survey of the Territories. In the final report, he wrote:

“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.

A decade later, one of the biggest names in American paleontology, Edward Drinker Cope, moved the fossils to the genus Dyplomystus. Then in 1907, David Star Jordan split Dyplomystus into two genera, and placed the Wyoming herring fossils in Knightia, where they remain to this day. Jordan named them Knightia to honor Wilbur C. Knight, the first State Geologist of Wyoming, and an “indefatigable student of the palaeontology of the Rocky Mountains.” Knight had recently died, in 1903—only 45 years old.

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).

Why so many fish fossils? Because fifty million years ago, great schools of knightias swam in the giant lakes of southwest Wyoming. During periodic die-offs, dead fish accumulated on the lake bottoms where they were entombed in dirt, debris and volcanic ash. Now they're immortalized in lakebed muck turned to shale—the Green River Formation.

“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.

Last Saturday, we celebrated the thirtieth anniversary of Knightia’s designation—at the Fossil Fish Festival. Experts gave tours of the Geology Museum and collections. Novice paleontologists prepared fossils, carefully scraping away shale bit by bit to reveal tiny bones. Others made fossil rubbings. Faces and arms were painted. We watched Your Inner Fish (very good movie), and even feasted on Knightia! … cookies that is ;-)

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.

Sources

Grande, L. 1982. A revision of the fossil genus Knightia… Novitates 2731 (American Museum of Natural History). PDF

Jordan, DS. 1907. Fossil fishes of California; with supplementary notes on other species of extinct fishes. Bulletin of the Department of Geology, vol. 5. Berkeley :The University Press. [Biodiversity Heritage Library http://www.biodiversitylibrary.org/item/139556]

Leidy, J. 1873. Contributions to the extinct vertebrate fauna of the western territories. Washington: Government Printing Office. [Biodiversity Heritage Library http://www.biodiversitylibrary.org/item/125566]

A walk up the Plant Evolutionary Ladder … all the way to flowers

Willow Canyon ahead, what will we find?

On February 12—midwinter—we headed for “Willow Canyon” on the east side of the Laramie Basin, at 7200 feet, in the interior of the continent far from moderating marine influences. Yet it felt like spring … sunny, warm (40º F!), and no wind.

The prairie was brown except for occasional small green blades along the dirt road. Aside from limber pines and Rocky Mountain junipers, trees and shrubs were bare. But after entering the canyon we found much of interest. Emmie wore herself out in her usual futile pursuit of rabbits (enthusiasm far exceeds ability). I was more successful, finding everything from mosses to flowers in what appears to be just another small dry limestone canyon in the foothills of the Laramie Mountains.

Starting low on the evolutionary ladder …

Mosses—no seeds, no vascular tissue.

Mosses lined rock ledges in a shady alcove in the canyon wall. They were surprisingly lush, rich green and moist with recent snowmelt. I saw only gametophytes, with no sign of this year's sporophytes (the two phases of the moss life cycle). The mix of shade and light made photography difficult, so I just shot and hoped for the best.

Mosses reside low on the evolutionary ladder because they produce spores instead of seeds, and they have no vascular tissue—which explains why they’re short. Conducting water very far is difficult without plumbing.

These moss clumps are aggregations of small individual stalks, gametophytes. There may be sex organs hidden at the tips of the gametophytes. If fertilized, female ones will grow into sporophytes (there's more in the elegant life cycle diagram mentioned earlier).

Clump of moss gametophytes, with a few dead sporophytes from last year.

An abundance of sporophytes; fairy for scale.

Lichens also thrived on the limestone ledges (orange and yellow mats above). I couldn’t place them on the plant evolutionary ladder as they’re not a single organism but three, in a beneficial partnership: an alga, a fungus and a yeast (the last is a recent discovery).

I found a few ferns too, though not in the shady alcove as you might expect but rather on exposed rock faces. Tough little cliffbrakes with thickish dull green fronds seem to grow directly out of the rock. This is western cliffbrake (Pellaea occidentalis), which is calciphilic as well as xerophytic—limestone-loving as well as drought-tolerant. [See Plants on Rock for more about plants of Willow Canyon.]

Plant is about 2 in across.

Ferns are vascular plants so are considered more advanced than mosses, but they too produce spores, not seeds. Below is a seed-producer. However its seeds are naked, indicating we still haven't reached the top of the ladder.

My favorite gymnosperm (“naked seed”) in the canyon is this limber pine (Pinus flexilis). It’s a really small “tree” but its life history is impressive: a seed germinated in a dry shallow crack, grew into a seedling, and managed to keep growing with just a bit of moisture and debris each year! The annual rings must be microscopic. Any guesses as to age?

Nearing the top of the evolutionary ladder, I found an angiosperm (“enclosed seed”)—a flowering plant. And it was flowering! This may be the only native species blooming in the wild in the Laramie Basin right now (can’t think of any other possibilities).

Well … barely blooming. White hairs were just starting to emerge beyond the bud scales.

North American pussy willows (Salix discolor) bloom long before leafing out. I followed this one in 2015, after discovering flowers on February 26. Leaves didn’t show up until May. It's a male, and the only willow in the canyon. It thrives in an alcove shaded by junipers, with moss at its feet, next to a small waterfall that runs after heavy rains.

Willow Canyon pussy willow two years ago, on February 26.

The willow thrives thanks to great habitat. Water runs off the rock wall, and large junipers provide shade.

I easily walked to the head of the canyon (almost no snow!) and then returned by way of the rim, stopping for a few more views of the willow of Willow Canyon.

Eponymous willow peeks above the canyon rim (center of photo).

Of course, these plants pale in comparison to those being posted by bloggers from warmer zones, where gardens already are filled with color, or from moister climes where walls and nooks are lush with mosses and ferns. But this is southeast Wyoming. This time of year, even the most modest plants thrill us! At the same time, I hope this crazy weather doesn’t prompt more plants to grow and bloom … and then get zapped by repeated hard frosts.

Coda

Though it felt like a spring day, winter made its presence known—best of all, in the form of ice art. Jack Frost produces terrific abstracts. Fortunately, several were still in place.

Jack can turn even the most mundane object into a thing of beauty … like a mud puddle:

Thanks to Beth of Plant Postings for the inspiration to look for plants on rocks in midwinter: It's Only a Rock Wall ... Or Is It?

A Powell Palmetto Perhaps?

Am I following a palmetto?

Sabal palmetto (source).

I’m intent on learning more about palms, as I decided to follow a palm tree this year (unfamiliar with tree-following? click on the link). My tree has a name, Sabalites, but what kind of palm is it? No one is sure. There are lots of choices—the palm family (Arecaceae) is large and diverse. It includes five subfamilies, 16 tribes, 2500 species, and many products consumed by humans: coconuts, dates, oil, betel chew, rattan and more. Most palms grow in tropical or subtropical regions, and occasionally in deserts.

Selected palms of the world; click on image to view details (source).

Palm fruit are beautiful as well as delicious (Dransfield et al. 2008).

Desert fan palms near Twentynine Palms, California (source).

When I lived in California, I was familiar with palm trees—specifically the ones planted along highways and in cities, and the native fan palms of desert oases, Washingtonia filifera. Then I moved to Wyoming where currently it’s much too cold for palms. However, fifty million years ago they lined the shores of huge lakes in the southwest part of the state. Even though their leaves are beautifully preserved in rocks of the Eocene Green River Formation (more here), no one is sure what kind of palms they were. Since I started following this tree, I’ve learned that plant fossil identification is really tough. Even the most challenging living plants are easy compared to fossilized ones.

Fossil Lake of Early Eocene Wyoming (Chicago Field Museum).

In 1870, geologist Ferdinand Vandeveer Hayden’s exploratory expedition stopped near Green River Station, Wyoming, where they found lots of fossils. Some looked very much like palm leaves. In the expedition report, staff paleontologist Léo Lesquereux assigned them to Flabellaria Eocenica. I don’t know why … modern day Flabellaria is not a palm, nor do the leaves resemble palm leaves.

Later, Hayden sent the fossils to paleontologist John S. Newberry of Columbia College, who decided they looked enough like today’s palmettos, genus Sabal, to call them Sabal powellii (I presume in honor of geologist John Wesley Powell, then Director of the US Geological Survey, but I haven’t been able to confirm this). The Powell palmetto was one of ten new fossil plant species from the Green River area published by Newberry in 1882.

8. SABAL POWELLII, n. sp. Leaves of medium size, 4 or 5 feet in diameter, petiole smooth, unarmed, terminating above in a rounded or angular area, from which the folds diverge; beneath concavely narrowing to form a spike 3 to 4 inches in length; rays about fifty, radiating from the end of the petiole, perhaps sixty in the entire leaf, compressed to acute wedges where they issue from the petiole, strongly angled and attaining a maximum width of about 1 inch; nerves fine, about twelve stronger ones on each side of the keel, with finer intermediate ones too obscure for enumeration. Formation and locality. — Eocene strata. Green River Station, Wyoming.

Why did Newberry conclude that these fossils were palmettos? Because the leaves are clearly costapalmate. (Yes, this is an esoteric term, but the concept is easy and useful.)

Costapalmate leaf of the Puerto Rican hat palm, Sabal causiarum (source).

Palm leaves are huge, with blades divided into many narrow segments arranged in several different patterns. In palmate leaves, segments fan out from the base of the blade—like fingers from the palm of a hand. In costapalmate leaves, the leaf stem (petiole) extends up into the blade to form a costa, where leaf segments are attached. The costa is only visible on the underside of the leaf, and from above, leaves look palmate. [Here’s a helpful webpage devoted to costapalmate palm leaves.]

In a paper about extinct floras of North America (1898), Newberry included a photo of a Wyoming palm leaf fossil with an obvious costa. “In the figures given, that on Pl. LXIII, fig. 6, represents the under side of the leaf at its base, showing [a] pointed spike [costa] formed by the prolongation of the petiole.”

From Newberry 1898; no scale provided (leaves can reach 4-5 feet across).

Unfortunately, costas are not unique to palmettos, and in 1930, paleobotanist Edward W. Berry overrode Newberry’s decision, renaming the fossils Sabalites powellii:

[the leaves] “are superficially much like the leaves of the existing species of Sabal, and their northern range appears to afford some corroboration of such a relationship, but this is by no means established, and it appears to me to be a better practice to refer such remains to the form* genus Sabalites rather than to Sabal.”

[*In form classification, fossilized organisms or their fragments are classified based on appearance, not biological relationships. If different parts of a single species are not obviously from the same source, they may end up as different form species or even genera.]

Robert Read and Leo Hickey agreed with Berry in their 1972 Revised Classification of Fossil Palm and Palm-like Leaves. They were adamant that leaves alone are insufficient evidence:

“Numerous similarities in the form and gross external features of [fossil] palm leaves make it difficult or impossible to assign them to modern genera based only on their external morphology. The uncertainty … becomes even greater with the limited, incomplete collections available to the paleobotanist. A modern specialist might speculate that a given fossil closely resembled a modern genus such as Sabal, Geonoma or Thrinax. Such a suggestion would be debatable since it is almost impossible to distinguish these genera … without seeing flowers, fruit or other diagnostic characters. Forced identifications with modern genera contribute nothing to evolutionary theory but give instead a confused picture of the floristics of the geological record. Since it is very difficult to identify specimens of modern palms accurately from their leaves alone, no attempt should be made to place fossil palm fragments in genera of modern palms unless unquestionably identifiable with them.”

Maybe we shouldn’t give up just yet. After all, thousands of fossils are collected from the Green River Formation every year! Maybe some will reveal the true identity of Sabalites powellii. There’s reason for hope. Paleobotanist Sarah Allen has been working nearby on another fossil palm, in the Bridger Formation, and has enough fossils—leaves, flowers and even pollen—to confidently assign the trees to Phoenix, the genus that includes today’s date palms (Allen 2015). Will we be so lucky with Sabalites? Already its fossils include not just leaves, but also apical buds, flowers, inflorescences (flower clusters), and even inflorescences attached to leaves. Are more discoveries likely? When I visit the remains of Fossil Lake later this year, I'll look for some experts and ask them what they think.

Fossil terminal bud, from the Green River Formation (in palms, leaves originate from a single terminal bud at the top of the trunk); University of Wyoming Geology Museum.

Personally, I hope paleobotanists find that Sabalites powellii is indeed a palmetto, and that they resurrect Newberry’s Sabal powellii. “Powell palmetto” has such a nice ring to it ...

We’re off to Fossil Lake to see the Powell palmettos!

Sources

Thanks to the Biodiversity Heritage Library for providing easy access to older paleontological literature, and to Mike for continued guidance in paleontology.

Berry, EW. 1930. A flora of Green River age in the Wind River basin of Wyoming. USGS Professional Paper 165: 67.

Dransfield, J., et al. 2008. Genera Palmarum, the evolution and classification of palms. University of Chicago Press.

Newberry, JS. 1882. Brief descriptions of fossil plants chiefly Tertiary. Proceedings US National Museum 5: 504.

Newberry, JS (A. Hollick, ed.). 1898. The later extinct floras of North America. Washington: Government Printing Office.

Read, RW. and Hickey, LJ. 1972. Revised classification of fossil palm and palm-like leaves. Taxon 21:129-137.