Tag Archives: Formations

Shark bites in the Cretaceous Sea

One of the most exciting things in paleontology is being able to definitively establish the interaction of two species from the fossil record. It is thrilling to picture a moment in time, millions of years ago, when two animals were at the same place, at the same time, and be able from fossil evidence to glean something about their interaction and behavior.

One dramatic example of this is finding a fossil with clear evidence that it was bitten by a shark. During the Late Cretaceous, North America was cut in half by an interior sea that extended the Gulf of Mexico across the mid-continent to connect with the Arctic Ocean in the north, effectively creating two land masses where today there is one.

In this last period from the Age of Dinosaurs, fantastic and strange creatures swam the seas. Today, the sediments from that ocean are exposed in badlands across much of western Kansas, Nebraska, and South Dakota. These geologic formations, like the Niobrara Formation, preserve a rich record of the ocean life, and clearly show what a scary ocean it was.

Tylosaurus model from the Carnegie Collection

Giant marine lizards thrived in the sea. These beasts, close relatives of modern snakes and lizards, were called mosasaurs. There were several kinds that likely had different modes of life, some making use of resources close to the surface, and other species specializing in deep-water feeding, with the largest of them reaching 50 feet in length. They were joined by another group of marine reptiles called plesiosaurs. Plesiosaurs occur in two basic body plans, with the unimaginative names of long-necked and short-necked for obvious reasons.

Long-necked plesiosaur Styxosaurus

The long-necked plesiosaurs have been described as looking like a turtle with a snake threaded through its shell. They had a stocky, turtle-like body, enormously long necks capped by a remarkably small head, and stumpy tails. They had four large flippers that helped to propel them through the water as well.

Short-necked plesiosaurs had large heads attached to short, thick necks. The long-necked forms most likely specialized in eating smaller fish with their small heads, maybe using their long necks to “snake” their way amongst their prey before being noticed. The short-necked forms obviously ate large prey, as evidenced by their massive heads and powerful jaws. (You can find models of both long and short-necked forms, as well as mosasaurs as part of the collection of dinosaur toys).

Living alongside these giants of the sea were animals that we would easily recognize, at least for their general body plan—these were the sharks. There was a significant amount of shark diversity in the Interior Sea as well, from relatively small forms that likely ate near the sea floor, to mid-sized forms that ate smaller fish and scavenged on dead carcasses, to several very large species that rivaled the modern great white shark in size and ferocity.

On occasion, when finding remains of fish or the marine reptiles, we find evidence of those remains having been bitten by sharks. The most compelling evidence is when teeth are found embedded in the fossil remains, but also punctures and tooth scratches can be a telltale sign.

Several plesiosaurs have been found as partial skeletons, with bites in several areas of their body, suggesting that after they died and settled to the ocean floor their carcass was scavenged by mid-sized sharks.

Cretoxyrhina bites the back of a mosasaur in the Late Cretaceous. Painting by Dan Varner.

And in one dramatic example, the great white of the Kansas seas bite the back of a mosasaurs, cutting a section of vertebrae completely out of the giant lizard. The section of back, with its included vertebrae, was later spit out by the shark after having been mostly digested. The gristly remains settled to the ocean floor to lie there for millions of years before being found and placed in a museum.

Today we are fascinated by tales of shark attack, with the movie Jaws being a prime example. You can learn about these dangerous animals in another post, but perhaps it gives you some comfort to know that the denizens of the ancient seas also were subject to shark bites!

Additional information about this specimen can be found at Oceans of Kansas.

What’s the difference between igneous, metamorphic, and sedimentary rocks?

There is something basic in our desire to classify things. Early humans no doubt looked around them at the natural world and instinctively began to group, and subgroup, things. Maybe they grouped things that flew, things that swam, things with leaves, or whatever. And, we have been doing it ever since, trying to create a taxonomy of the natural world that helps us to make sense of it.

Trouble is, our taxonomies are always a best guess, or an approximation, of nature, and this is very evident in the three major groups of rocks. Introductory geology students are usually taught about igneous, metamorphic, and sedimentary rocks, but this really is an oversimplification of nature.

Igneous rocks are those that form from a full melt, where the mineral material is completely turned to a liquid state. From a hot, liquid state, the mix is cooled at various rates and under various conditions to create a variety of igneous rocks. If the mixture cools underground, we call the liquid rock magma, and the rock that forms from it is called an intrusive igneous rock. If the liquid comes to the surface and cools faster, we call it lava, and the rock is an extrusive igneous rock.

Sedimentary rocks generally start with any of the already-formed rock types, and through weathering, transport, and re-deposition, lay down new rock combinations. For example, weathering of a rock may form sand-sized grains that get transported to a beach where it is later solidified into a rock called sandstone. There are other common sedimentary rocks like shale, siltstone, and limestone.

Metamorphic rocks are the hardest to understand in concept, I think. This process is similar to igneous in that it involves heat to cook the rock, but for metamorphic rocks the process does not progress to a full melt of liquid rock. Instead, the heat, and often high pressures of geologic processes, transforms the mineral and rock structure. This is common in mountain-building processes, where the intense pressure of tectonic plates colliding squeezes the rock with immense pressures.

Geologists name the layers of rock that we map to help unravel geologic history. There is a whole code for the naming of rock formations.

But this neat taxonomy of igneous, metamorphic, and sedimentary is not always clear-cut. Many rock types are really a combination of processes; we should not expect that nature falls into our simple categories. Take ash fall deposits for example. Ash is spewed from volcanoes during an eruption (an igneous process) and then blown across the landscape, often forming very thick deposits (a sedimentary process). There are several examples of ash like this across the Central Plains, far from where the ash originated. One prime example is at Ash Fall State Park in central Nebraska where a herd of rhinos was buried by a thick ash deposit.

Travertine is another rock that has a mixed origin. Water is heated at depth by proximity to magma (igneous) and picks up minerals. The water can then travel to the surface where it cools and deposits the minerals layer upon layer (sedimentary), building up travertine. This rock often has interesting texture and colors due to mineral impurities, making it a nice decorative stone used for tiles.

So, we start with basic guidelines as way to understand geologic processes. I have described this as “lying” to intro students, not maliciously, but by giving them principles that are true enough, but oversimplified. If you go on in geology you spend the rest of your education learning the exceptions to the rules.

My National Geographic moment

“A photographer from National Geographic wants to talk to you.” These words, or words to those effect, met me as I came into the museum office one day back in 2001, and they definitely caught my attention.

It was 2001 and I was Assistant Director of the Sternberg Museum of Natural History. We had just reopened the museum in its new location in Hays, Kansas, a few years before in 1999. The museum had enjoyed some tremendous success at attracting visitors and media attention from across the state. And now someone from National Geographic wanted to talk to us? Wow. I returned Jonathan Blair’s call and began an unusual week of activity.

It turns out that the magazine was going to run a story on pterosaurs, the flying reptiles from the Mesozoic, and they hired Jonathan to get pictures to illustrate it. He had already traveled to some of the great museum collections for pterosaurs in Europe and the United States, but he wanted to visit Sternberg. The Sternberg’s collection of pterosaur material is about the third or fourth largest in the nation, and very significant.

The Sternberg Museum, on the campus of Fort Hays State University, was managed for many years by George F. Sternberg, famed fossil collector. He spent his free time out in the chalk, the Niobrara Formation of western Kansas, collecting the fish and swimming and flying reptiles that left their remains millions of years ago. Sternberg supplemented his salary at the museum by selling specimens to other museums, but if he collected something really nice it went into “his” museum. Over the years, the museum’s collection grew in size and quality.

Besides our amazing collection of fossils, Jonathan had heard about our life-sized pterosaur models we had just installed in our walk-through Cretaceous exhibit. And he had a crazy idea—let’s take a life model of the beast and “fly” it over the very rocks where its remains can be found. He wanted to take one of our life-sized model and photograph it over the chalk beds.

Well, I can bend over backwards for National Geographic, but taking one of our brand new models down from the ceiling, which had not been easy to install in the first place, and which since had walls built up around them, and truck them 70 miles to hang from a crane in the chalk sounded a bit risky to me.

But I did offer to help in any way we could, so I did the next best thing—I found him another pterosaur model.

Over the next several days we made plans and preparations for the big event. We needed to get the model that I was able to find shipped to the museum. It had been kept in storage and was a little beaten up, but the company that supplied it sent a staff member to clean, fix it, and touch up the paint for its big moment. The model, being life-sized, had a twenty foot wing span, flimsy neck with a large head at the end, and feet that stuck out the back, giving the whole thing a cross shape, making it too long in any direction. Not exactly the easiest thing to get into a truck and ship!

We scouted a location for the big photo shoot. I took Jonathan to the Castle Rock area, a well-known outcropping of the chalk that has easy access and grand vistas. We needed to secure special permission as we were going to bring in a crane and another truck to transport the pterosaur model.

We needed to arrange for a crane to make the 70 mile one-way trip from Hays to the chalk beds. On this, and on so many other occasions, I marveled at the “can do” spirit of western Kansas people. You want something done just ask a former farm kid. While he might look at you funny, he will get it done.

In between all this activity, I remember some spectacular meals shared with Jonathan, listening to his many adventures from around the world while taking photographs. He also shot pictures around the museum, and he took a couple of photos of me that I have cherished ever since.

Greg dusts the life-sized models of Pteranodon sternbergii in the Sternberg Museum of Natural History

Greg dusts the life-sized models of Pteranodon sternbergii at the Sternberg Museum of Natural History. Photograph by Jonathan Blair.

The big day arrived and all was going well. The weather cooperated, the truck was loaded with its ungainly cargo, and the crane made it to the site. We had also brought along a number of crew members to help hold the model. We wanted to lift it into the air for the photograph, but if you know anything about western Kansas, you know it is windy. I was not sure what would happen when you lifted such a thing into the gusty winds, and how hard it might be to control. The only control we had were guy-wires coming down from the wing tips to hold it against unruly behavior.

With trepidation we gave the signal to the crane operator to lift, and the hundred pound model took to the air. And in the end, the wind was no issue—the model, like the animal it represented, was built for the air. It found a comfortable equilibrium and settled into the wind easily. Jonathan snapped his pictures, and just like that we had what he had come after.

Life-sized model of a pterosaur, an ancient flying reptile, soars onces again over western Kansas

Life-sized model of a pterosaur, an ancient flying reptile, soars once again over western Kansas

We took more photos at a few other locations, all of which could have made fantastic desktop images, but he knew he was done. We packed up and came home, and all those days preparation resulted in the lead image for the story. It was all Jonathan’s photo and idea, and I enjoyed the part I played in making it happen—one of the perks for working at a museum.

See the National Geographic story.

Jonathan Blair’s web page

Spending time in Purgatoire

One of the many places that I have been fortunate to spend time in is Purgatoire. Perhaps not the same thing you are thinking, but I am referring to the Purgatoire River Canyon in southeastern Colorado. Located south of La Junta, this area is an often-overlooked gem. The scenic vistas could be used for your desktop wallpaper!

Purgatoire River Canyon in southeastern Colorado

The many names applied to the region can be confusing. The Purgatoire River has cut a dramatic canyon in this part of the plains, and with the Rocky Mountain Front Range far to the west, it can be almost startling to come upon the deep canyon in an otherwise rolling plains landscape. Anglo settlers bastardized the name of the river, and instead of the eloquent Purgatoire, ended up calling the area Picket Wire, so both names alternately apply.

The area is managed predominately by two federal agencies, the United States Department of Agriculture’s Forest Service and the Department of Defense through the Army. The military uses their lands for maneuver practice, as I understand it, tanks and other mechanized equipment. Some years ago the Army carved off some of their land and gave it to the Forest Service to manage as part of the Comanche National Grassland. The Forest Service land is used for recreation and also the preservation of significant historic and prehistoric resources.

Petroglyph of human and horse figures

Rourke Ranch house in the Purgatoire Canyon

The historic resources include Native American petroglyphs and other archeological sites, early Spanish homestead sites and churches, early American homesteads. The prehistoric resources include dinosaurs and other prehistoric animals, both body fossils and trace fossils. I was very fortunate to have been involved in the documentation of some of the first dinosaur fossils from the region (Schumacher and Liggett 2004).

Dinosaur trace fossils, in particular dinosaur tracks, are well preserved in one section of the Morrison Formation in the bottom of the canyon. These tracks were discovered in 1935 by a young girl as can be seen in this newspaper clipping from the Topeka Capital Journal. However, the tracks are most definitely not those of a Tyrannosaurus rex (mentioned in the clipping) as that beast did not stalk the Earth for at least 90 million years after the track-makers walked here. This track site is the largest continuous track site of dinosaurs known from North America, and contains over 1,400 prints.

Newspaper clipping announcing the discovery of the Purgatoire track site

However, because of the remoteness of the site, scientists turned their attention to other dinosaur tracks found in Texas, and the Colorado tracks were essentially forgotten for many decades. However, a newer generation of scientists have re-examined the track site. Of interest is the fact that the site shows five parallel sauropod tracks, suggesting that at least in this case, the animals walked along together spread out, not walking in a line (Lockley 1991).

There are actually several track layers in the rocks. Also preserved are several three-toed theropod, or meat-eating dinosaur. While it is difficult to exactly match the track to the species of dinosaur that made them, the large sauropod tracks were made by an animal like Apatosaurus (Brontosaurus of old) and the meat-eating tracks are similar to what an Allosaurus would make.

A well-preserved theropod dinosaur track in the Purgatoire Canyon

View of the Purgatoire River track site using low altitude photography

In addition to the tracks, the canyon is also now yielding body fossils of dinosaurs. It is really no surprise since the Morrison Formation is extensively exposed along the river canyons. The Morrison is the name given to a wide-spread formation that is the most prolific producer of Jurassic dinosaurs in North America. The formation outcrops in North Dakota, South Dakota, Montana, Wyoming, Colorado, Oklahoma, Texas, New Mexico, Arizona, Utah, and Idaho. Every Jurassic dinosaur you have ever heard of comes from the Morrison; animals such as Allosaurus, Apatosaurus, Diplodocus, Stegosaurus, and Camarasaurus all come from this formation. (See Formations for information about what that means.)

Stratigraphic section of the Purgatoire River Canyon showing the geologic formations that outcrop

Given the Purgatoire River’s remoteness, and the fact that it was controlled for many years by the Army, few people were able to explore the region until more recent decades. Thus, now it is one of the last areas of the Morrison Formation exposures to be explored. And it is proving to be as rich as expected.

Over the last decade, the Forest Service has been conducting Passport in Time (PIT) programs in the canyons, looking for new dinosaur sites, and excavating sites. Many people, scientists, graduate students, and the lay public have enjoyed excavating dinosaurs in this beautiful and remote canyon. And several significant specimens have come out of the area. The Forest Service has partnered with many museums from the region to study this treasure-trove and to allow people to enjoy this amazing region.

Volunteers excavate dinosaur fossils from the Woody site

Dinosaur vertebra from the Woody Site being prepared at the Sternberg Museum of Natural History

Plastered dinosaur bone being carried out of the LC Site

Volunteers excavate dinosaur bones from the Morrison Formation at the LC site

The Forest Service offers tours of the canyon and track site. If you are interested contact the Forest Service Office at 1420 East 3^rd, La Junta, CO 81050, 719-384-2181. If you plan to visit the area on your own, be aware of a couple of things. You cannot drive into the canyon without prior authorization. You can hike in on your own, but it is several miles in and out, and the summer temperatures can be brutal, so bring plenty of water and plan accordingly.

A large section of Dakota Formation slumping away from the main block provides a dramatic hiking experience

Lockley, M. G. 1991. Tracking Dinosaurs: A New Look at an Ancient World. Cambridge University Press, New York.

Schumacher, B. A., and G. A. Liggett. 2004. The dinosaurs of Picketwire Canyonlands, a glimpse into the Morrison Basin of southeastern Colorado. Journal of Vertebrate Paleontology 24(Supplement to 3):110A. (Poster page 1 and page 2).

Many other dinosaur facts can be found here at Boneblogger. Just search or select the category.

Dinosaurs dragging their bellies—Huh?

Isaac Newton famously wrote in 1676,“If I have seen further it is by standing on the shoulders of Giants.” This gets to the heart of the scientific process—a gradual addition and refinement of human knowledge and understanding of the natural world. But, of course, sometimes even giants had wacky ideas.

The particular “giant” to whom I refer is Charles H. Sternberg, famed fossil collector. Sternberg began collecting fossils when he was seventeen, at a time when it was not exactly commonplace, in about 1867. And he dedicated his life to this unusual pastime, founding a family of fossil collectors when his sons continued the tradition for a second generation. Together, the Sternberg family collected a huge number of fossils for museums and science. There is hardly a major museum in the world that does not have one of their discoveries on display.

Sternberg started his career in the hills of western Kansas, collecting fossil plants from the Dakota Formation. He sent his specimens back to the young Smithsonian Institution, for which he received a letter of acknowledgment that he treasured his whole life. He was bitten by the “fossil bug.”

A rare photograph of Charles Sternberg (right) with his twin brother Edward (left).

By 1875, he enrolled in college where he studied briefly under Benjamin Mudge. Mudge organized a fossil collecting trip for 1876 to collect for O. C. Marsh, the Yale College paleontologist. Sternberg was too late to sign up with Mudge, and bitterly disappointed, and somewhat brazenly, he wrote a letter to Edward D. Cope, Marsh’s rival.

Sternberg wrote, “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. I said, however, that I was too poor to go at my own expense, and asked him to send me three hundred dollars to buy a team of ponies, a wagon, and a camp outfit, and to hire a cook and driver. I sent no recommendations from well-known men as to my honesty or executive ability, mentioning only my work in the Dakota Group.” (Sternberg 1909, pg 33).

Sternberg anxiously awaited a reply, and when he opened Cope’s letter, a draft for $300 fell out, a very significant sum. So began his professional fossil hunting career. Over the years he collected throughout the American and Canadian west. In the twilight of his career he semi-retired to San Diego, and was allowed to use the title of curator at the natural history museum.

Museums and libraries are marvelous places, full of fascinating treasures. It was while reading in the archive at Fort Hays State University’s Forsyth Library that I came across a carefully saved clipping of an article from the Los Angles Time Sunday Magazine from December 20, 1931, titled “The habits of dinosaurs,” written from an interview with the 80 year old fossil collector.

In the article, Sternberg is quoted as giving his vision of the life of some of the dinosaurs that he had collected over the many years. While I recognize that it is not really fair to judge the views of earlier experts, especially with the perspective of almost three quarters of a century of additional knowledge, but it can be damn funny.

Sternberg is quoted as authoritatively saying, “Dinosaurs were lizards. They stood and walked like lizards, not like elephants or rhinos. That is to say, the normal positions of their feet were outside the line of the body, just like the alligators of today, not inside or even with the line of the body, as are the feet of horses, elephants and other mammals. Moreover, the dinosaur, instead of standing up, on straight legs, as usually pictured, bent its legs outward, as do the lizards, and dragged it belly on the ground, again like the alligators, monitors and other large lizards of the present day.”

Dinosaur reconstructions of that period typically showed dinosaurs with spindly, lizard-like limbs, and tails dragging, but with a generally upright posture. Sternberg evidently did not agree, arguing in favor of his views with some odd reasoning.

Citing fossils of preserved dinosaur skin, he said, “Furthermore, the skin on the lower side of the abdomen of this dinosaur was much thinner and more delicate than on other parts of the body. This is further and strong argument for my claim that the dinosaur dragged its belly on the ground, as do the alligators of today, which so protect their vital parts from carnivorous animals…you may be sure that no tender-stomached dinosaur, whether it weighed forty tons or forty pounds, would voluntarily expose its tenderest and most vital parts to attacks by the tyrant dinosaur or any other carnivorous creature by walking erect.”

Illustration from Los Angles Times Sunday Magazine, 1931

Illustration from Los Angles Times Sunday Magazine showing Sternberg's idea of dinosaur stance.

I totally agree. I hate walking around with my “tenderest” parts exposed. The accompanying illustration of Sternberg’s vision of the Mesozoic is hilarious, with giant sauropod (long-necked) dinosaurs hunkered down, presumably guarding soft spots. I am not really sure how Sternberg expected it would work for a forty ton animal to push itself along the ground with its legs sprawled out to the side, much less how it would support its own weight on its chest, but details, details.

Even though the article claims that Sternberg was a “man of facts and not fancies,” he was prone to exuberant musing about the prehistoric beasts he collected. While he could be wacky, we owe a great debt to the entire family for their contributions to science.

Further reading about the Sternberg family:

Everhart, M. Oceans of Kansas website, summary of the work of Charles H. Sternberg.

Everhart, M. J. 2005. Oceans of Kansas: A Natural History of the Western Interior Sea. Indiana University Press, Bloomington.

Liggett, G. A. 2001. Dinosaurus to Dung Beetles: Expeditions Through Time, Guide to the Sternberg Museum of Natural History. Sternberg Museum of Natural History, Hays, Kansas.

Rogers, K. 1991. The Sternberg Fossil Hunters: A Dinosaur Dynasty. Mountain Press Publishing Company, Missoula, Montana.

Sternberg, C. H. 1909. The Life of a Fossil Hunter.

Other interesting dinosaur facts are found here at Boneblogger. Search or select the category for more.

Sternberg, C. H. 1917. Hunting Dinosaurs in the Bad Lands of the Red Deer River Alberta, Canada. Charles H. Sternberg, San Diego.

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