A work in progress... bear with us as we grow!
Working the Quarries:
Working in the quarries is perhaps the single most rewarding aspect of our research. In this display, we have molded an actual quarry wall from one of our quarries and installed it here. You can see that the bones are distributed in the quarry as a normally graded bed with larger bones at the bottom and smaller bones towards the top. What does this tell you about how the bones came to be here? Could they have accumulated slowly in this location, or must they have come all at once (1)? This is a very important observation that we were able to quantify because of our use of high resolution GPS for mapping all the bones in the quarry. Included in the display is a functioning GPS rover that we use to make the positional measurements, accurate to less than a centimeter (just over ¼ inch). This functioning unit, one of several that we use, was donated by Mark Silver of iGage Corporation in Salt Lake City, and cost over $20,000 new. It is not only operational, but is actively taking measurements of its position.
- 2015 Weeks, S., Chadwick, A. and Brand, L. Large dinosaur bonebed deposited as debris flow: Lance Formation Niobrara County, Wyoming. Geological Society of America Abstracts with Programs. Vol. 47, No. 7, p.566
The research we are conducting on the site in Wyoming is taphonomy. The taphonomist attempts to reconstruct all of the events surrounding the death and subsequent history for the fossils, including activities at the time of death, cause of death, events surrounding burial, and the post burial changes that have resulted in the bones being as they are today. Taphonomy is not only important for reconstructing the history of fossils, but is also an important discipline in criminology today. Taphonomists are often employed in crime scene investigations to determine the cause of death, the time of death and other aspects of the crime scene from evidences present at the scene. Today, you are the taphonomist. Looking at the quarry wall, what can you say about the fate of these animals? Keep that question in mind as we move on to consider the question: What can we infer about the environment of the dinosaurs at the time they met their demise?
Environment of the dinosaurs:
Did the dinosaurs die where they were living, or did they die elsewhere before they were transported to their present location? What kinds of geological events could explain the demise of many thousands of animals found in this one deposit? Was it an earthquake, an asteroid impact, a global scale flood, or a massive volcanic eruption? Or maybe more than one of these, or even all of them at once? Or something else? These are the kinds of questions that we are seeking answers for. Some of the possibilities come from the study of the sediments themselves. Were they deposited slowly over long periods of time, or did they accumulate rapidly, and even catastrophically?
One of the discoveries we made during our work on the bones was the presence of numerous sandstone layers in the Upper Cretaceous Lance Formation that had been disturbed by earthquakes (1). Such deposits are called seismites. One gigantic seismite is depicted in the background of this display. It is in a 5 meter (15 feet) thick bed of sandstone. The underlying bed is not disturbed, and the overlying contact is flat. But the sandstone bed itself is severely disrupted as if it had been shaken vigorously while still water saturated. The 5-meter-thick bed of sand was deposited so fast that water trapped by the sand during deposition did not have time to escape before the area was hit with an earthquake of catastrophic proportions. This caused the disruption of the orderly internal structure of the bed, and paints a picture of rapidly accumulating sediments in deeper water in a tectonically (earth movements) active environment. Many such beds are present in the Lance Formation. What does this tell us about the sedimentary environment of the dinosaur-bearing sediments?
The plant materials associated with the dinosaur bones include beautifully preserved microscopic pollen grains and spores, some of which are shown photographically in the lower right corner. The red color is a stain used to visualize the light yellow grains. We also find petrified wood, lea impressions, seeds, coalified wood, amber (petrified plant sap), impressions of plants and even a flower. While these plants, like the dinosaur remains themselves could have been transported a significant distance to their burial spot, they may have been associated with the animals in life. We also find various invertebrate forms including clams and snails, also seen here. Much more taphonomic information can be gleaned from the study of these non-vertebrate (vertebrate animals are animals with backbones) remains. What do you think happened?
2011 Weeks, R. and A. Chadwick. A prominent seismite in the Upper Cretaceous Lance Formation in northeastern Wyoming as a stratigraphic marker. Geological Society of America Abstracts with Programs, Vol. 43, No. 5, p. 280
The Other Vertebrates:
Not all of the vertebrate animals we find are dinosaurs. Among the dinosaur remains in our quarries are evidences of a wide range of other vertebrate forms, mostly associated with water. These include fish, amphibiians, lizards, alligators and crocodiles, and turtles. The fish include Amia (the bowfin), Lepisosteus (the gar), several species of stingrays and batfish, and sharks. There are also small shrew-sized mammals of forms unfamiliar to us today called multituberculates, because their teeth have many bumps of tubercules in rows, and opossum-like marsupials. Mammals and dinosaurs both occur as fossils in middle Triassic rocks. They do not appear to change much through the rocks of the Mesozoic, and the marsupials would be easily recognizable to us as opossum-like. What do the non-dinosaurian vertebrates tell you about the taphonomy of the dinosaurs?
What makes an animal a dinosaur? The only universal characteristic shared by all dinosaurs and not found in any other taxa is found in the structure of the acetabulum. The acetabulum is the place where the hip bones come together that holds the head of the femur and connects the pelvic girdle to the legs. Most typically, as is the case in our bodies, the acetabulum is entirely closed at the back by bone, so it forms a cup for the head of the femur. In dinosaurs, and in no other forms, the acetabulum was open, meaning that the back of the structure was not sealed off by bone.
Furthermore, the two great orders of dinosaurs are also differentiated by the relationship of the bones around the acetabulum (the pelvis). The giant sauropods and carnivorous theropods all have the lizard-like hip with the forward pointing pubic bone (Saurischia). While the herbivorous dinosaurs all have the bird-like hip with the backward pointing pubic bone (Ornithischia). Thus the hips are really important for dinosaur taxonomy.
The Dinosaurs: Edmontosaurus
For our main bonebed, Edmontosaurus annectens, the duckbilled dinosaur, is king. Nearly 90% of the bones we find there are either identified as Edmontosaurus or could be safely assumed to be from this taxon. This display is intended to give you a feel for just how big and what an amazing creature this animal was. Some of his features:
He eats grass like an ox. Edmontosaurus was herbivorous, a plant eating dinosaur.
His strength is in his loins. Like most small and midsized dinosaurs, Edmontosaurus walked primarily on his massive hind legs.
He moves his tail like a cedar tree. Edmontosaurus had a tail that was a meter thick at the base and several meters long.
His bones are as strong pieces of brass. Please examine the Edmontosaurus bones in the case and elsewhere in the museum. Of course, these are petrified bones, but the size and weight of these bones is immense.
His ribs are like bars of iron. Look at the rib on display.
Edmontosaurus was a formidable creature, at maturity, as large as the largest Tyrannosaurus. It seem likely that mature, healthy Edmontosaurus could easily outrun Tyrannosaurus and other predators, as this was their only known defense.
The Dinosaurs: Herbivores
Most herbivores are members of the Order Ornithischia, the bird-hipped dinosaurs. In our site we find the following ornithischian dinosaurs:
Edmontosaurus – the duckbilled dinosaur
Triceratops – the three-horned dinosaur
Pachycephalosaurus – the bone headed dinosaur
Thescelosaurus – sheep-sized dinosaur
Nodosaurus – armadillo like armored dinosaur
The Dinosaurs: Carnivores
The carnivorous dinosaurs of the Lance Formation are all members of the Order Saurischia, the lizard-hipped dinosaurs. Several of them are only known from teeth, although we are finding more bones of these fascinating dinosaurs each year.
Tyrannosaurus – the king of carnivores
Nanotyrannus – a smaller cousin of Tyrannosaurus
Struthiomimus – the ostrich mimic dinosaur
Anzu – the large oviraptor
Dromaeosaurus – the raptor alliance
Troodon – the small chicken sized dinosaur