Big toes! Huge bird!!

Along the rim of Bull Canyon, on the north slope of the La Sal Mountains in southeast Utah, my field assistant and I followed footprints in sand. Three-toed two-footed creatures had passed this way when the sand was wet, before it turned to rock. They were common then, traveling in packs.

Similar 3-pronged impressions occur 2000 miles to the east, in the Connecticut River Valley in Massachusetts. Some are famous—among the earliest to be studied and published. They were found in 1835 by Dexter Marsh, who was laying a flagstone sidewalk. He showed the slabs to the owner of the property who gave them to a physician who then gave them to state geologist Edward Hitchcock.

"They consist of two slabs, about forty inches square, originally united face to face; but on separation, presenting four most distinct depressions on one of them, with four correspondent projections on the other; precisely resembling the impressions of the feet of a large bird in mud." (Hitchcock 1836, italics mine)

Sandstone slabs, each 36.5" x 34"; depressions (molds) on left, projections (casts) on right (source, click on "Fossil Slabs Found by Dexter Marsh").

Hitchcock was understandably excited. Very few bird fossils had been found anywhere, and geologists had decided that because most birds were lightweight creatures of the air, they were unlikely to be submerged and preserved on the bottom of lakes, oceans and such. "Even when they chance to perish in the water, they float so long upon the surface, as to be most certainly discovered, and devoured by rapacious animals."

1. These impressions are evidently the tracks of a biped animal. For I have not been able to find an instance, where more than a single row of impressions exists.

2. They could not have been made by any other known biped, except birds. On this point, I am happy to have the opinion of more than one distinguished zoologist.

3. They correspond very well with the tracks of birds.

Some of Hitchcock's drawings of modern-day bird tracks, from his 1836 publication (source).

However, many of the tracks Hitchcock studied were too large to have been made by the birds we know—to 18 inches long and 13 inches wide, and separated by 6-foot strides. Therefore these tracks must have been made by large birds now extinct. Eminent geologists of the day agreed with Hitchcock (2). But by the end of the century they had been "proven" wrong. These tracks were not avian, they were reptilian (Dean 1969).

Science marches on of course, and we now know that in a sense, Hitchcock and his colleagues were correct. The creatures that left footprints in the Connecticut River Valley and southeast Utah were indeed birds. But they also were dinosaurs, specifically theropods (study the images below before discussing this at cocktail parties).

Dinosaur classification (3). While all birds are dinosaurs, not all dinosaurs are birds; similarly, birds are a subset of theropods (from Zureks).

Evolution of birds from a dinosaur ancestor; Manti-La Sal National Forest, Bull Canyon Tracksite.

You might be wondering why dinosaurs traveled the rim of Bull Canyon. Well ... actually they didn't. There was no Bull Canyon 157 million years ago. Instead this was a broad coastal plain, where large bipeds could cruise along at 2.5–3.5 mph (Hunt-Foster 2016).

The Bull Canyon Tracksite includes at least 50 well-preserved large theropod tracks, to 18 x 14 inches in size. But aside from footprints little is known about these creatures, for no bones have been found. So rather than naming a species, paleontologists named their tracks: Megalosauripus. These are ichnofossils—"a fossil record of biological activity by lifeforms but not the preserved remains of the organism itself." They're also called trace fossils, the term I learned.

Theropods passed this way, in a pack perhaps.

They were big! (40-pound dog for scale).

Megalosauripus is a theropod track, not the theropod itself.

The wet sand where theropods once walked is now sandstone, part of the Moab Member of the Curtis Formation, dating from 157 million years ago (Late Jurassic). The setting was dynamic—changing sea level, oscillating shoreline, occasional sand dunes—making classification and dating of rock units difficult (Mathis 2021). But no matter. Whatever geologists decide to call the rock, its theropod tracks go on and on and on. They occur across Arches National Park, east to the Bull Canyon area and the Colorado–Utah state line, and perhaps as far south as Blanding. This is the Moab Megatracksite, also known as the Dinosaur Freeway. A conservative estimate of its size is 700 square miles; as of 2016, c. 3000 tracks had been reported from 30 sites (Hunt-Foster 2016).

Dinosaur Stomping Grounds, aka Jurassic Dancefloor, with at least 2000 theropod tracks (Sierra Club).

Our visit to the Bull Canyon Tracksite last fall was but a brief introduction. Many more opportunities to commune with large extinct birds await. Fortunately many of the sites are on public land, and there's a handy guide available (Hunt-Foster 2016). We shall return!

Dreaming of giant birds after a day in the field.

Eye of the Ichthyosaur

My visit to the volcanoes of eastern California last May was far too short, but there was nothing I could do. Life called. So after hiking up Panum volcano I raced east past Mono Lake, crossed into Nevada in the Bodie Hills, stopped briefly for gas and groceries in Hawthorne, and raced on. My destination was Berlin in the Shoshone Mountains.

This would be my third attempt. The first was canceled by the covid pandemic. Then the park shut down while pandemic stimulus funds were used for road improvements (still unpaved and washes out occasionally, so check before going). But this year I made it, just in time to set up camp before dark.

Looking west from Berlin across Ione Valley to the Paradise Range beyond, a fine example of the basin-and-range topography that covers much of Nevada.

Berlin is one of Nevada's many abandoned gold-mining towns. It was at its peak at the turn of the century (19th–20th), with a population of about 250 miners and their support staff: blacksmiths, woodcutters, charbonniers, a doctor, a nurse, and a prostitute. Yet by 1911 everyone was gone, a typical boom–bust story. But Berlin didn't disappear entirely. Some buildings remained intact long enough for history buffs to drum up protection.

Berlin Mill in 1910.

Two stamp batteries center bottom, for crushing ore plus water and mercury.

Several decades later Berlin experienced a revival of sorts, thanks to the many curiously-shaped stones in a draw nearby (miners supposedly used them as dinner plates!). In 1928 paleontologist Siemon Mueller of Stanford University examined them, and determined that they were fossilized bones of large marine reptiles—ichthyosaurs. But he left the fossils in place due the remoteness of the site.

 

For geologist and bishop Nicholaus Steno, science was a way to understand God's work (source).

On the morning of August 13,1894, mason Michael Bergin picked up a stone to add to the new Episcopalian church in Laramie, Wyoming. But upon inspecting it, he spotted a fossil very different from the others he had found.

"CURIOUS FOSSIL. Found in the Sandstone Rock of the Cathedral" announced a headline in the Laramie Boomerang (newspaper) later that day. "It is a shell exactly like a miniature buffalo head ... the solid part corresponding to the head is about an inch in diameter, the horns about an inch long and three inches from tip to tip." Bergin set the stone aside for Professor J.D. Conley, curator of the University of Wyoming Museum.

Stonemasons at St. Matthew’s Cathedral regularly found fossils, saving the better ones for Professor Conley. He had already identified the clam-like allorisma, snail-like bellerophon, and pinna, which resembled a razor shell oyster. "The professor is gathering facts to put into a bulletin on the subject," explained the Boomerang.

But the article ignored the remarkable mystery these creatures implied. They were marine—all inhabitants of oceans. Yet the stones were quarried just east of Laramie. How did sea shells end up so far from a sea, and 7000+ feet above sea level?

A Persistent Question

Four centuries earlier, in the Apennine Mountains of Italy, scientist Nicholaus Steno asked the same question, but in Latin: “Quomodo res marinae in locis a mari remotis derelictae fuere?” How was marine life abandoned in places far from the sea?

No answer was immediately forthcoming. In the 1600s, geology did not exist, and knowledge was strongly shaped by church teachings, which did not address things like sea shells high in the mountains. Steno had to rely on field work and his own clever mind to solve the puzzle.

After examining many specimens, all of which looked like sea shells down to the finest level of detail, he concluded they were sea shells, now entombed in rock. They must have risen from sea level, thousands of vertical feet! This meant the surface of the Earth was dynamic, changing dramatically since the Creation. Steno's findings contradicted strict biblical interpretation—that God had created an immutable Earth—but the Church did not object. Science was increasingly seen as a way to understand and appreciate God's work.

Steno's interpretation of an angular unconformity, from his Prodromus, 1671.

Yellow very roughly outlines the Casper Formation (above and below ground).

With an able imagination, you can tour the Laramie area 300 million years ago. Start in a dune field at the foot of the Ancestral Front Range. Venture into shallow waters of the Paleozoic sea and then to its depths. At the final stop, careful beach combing should turn up some of its ancient inhabitants.

"Grotto at Sand Creek"—S.H. Knight photo, 1899 (AHC).

2. Visit Roger Canyon to see the Paleozoic seafloor up close. From Reynolds St. in Laramie, go north on 9th about 0.7 mi to where it becomes Roger Canyon Rd. ZERO YOUR TRIP ODOMETER HERE. At 6.9 mi ("No Winter Maintenance" sign) stop in the tiny turnout right (private land; stay on shoulder). Across the road is the reclaimed university quarry. Here the Casper is limey sandstone (well-cemented). Head up the canyon. At 8.0 mi, you will enter public land and limestone—having traveled back in time to when the water was deeper and the seafloor covered in limey muck. Public land continues for about a mile.

I too wended my way to this wonderful group of chalk outcrops.

“At first glance Kansas is_________, but there are_________things to see.”

The first blank contained words like boring, monotonous, covered in corn, flatter than a pancake. The second would counter with interesting, unusual, entertaining, educational, surprising, etc.

Some of my own impressions match the first blank: mile after mile of corn and sorghum (milo), orthogonal networks of perfectly straight roads, very few people except in widely-scattered small towns, and expansive vistas with little topographic relief (Kansas truly is flatter than a pancake, as has been shown scientifically (1)).

Pancake on left, Kansas on right (1).

Modern-day creature of the chalk. This tarantula was 15 ft up, crawling straight down the face!

Tylosaurus, the Kansas marine fossil.

Little Jerusalem, Kansas (source).

Chalk in a small draw on the Smoky Valley Ranch.

“One common method of quantifying ‘flatness’ in geodesy is the ‘flattening’ ratio. … we approximated the local ellipsoid [for both Kansas and a well-cooked pancake] with a second-order polynomial line fit to the cross-sections. These polynomial equations allowed us to estimate the local ellipsoid’s semi-major and semi-minor axes and thus we can calculate the flattening measure f.” Full details here.

(2) Other posts about Kansas Chalk: To Kansas to See the Chalk, A Ghost Rock Speaks and Charismatic Kansan Megafauna.

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!!