Museum of Natural History - Dinosaur Hall Self-Guided Study

This display was constructed in the early 1980s, and thus there have been changes in our views and names of the dinosaurs. We will try to note some of them here. However, it is the hall with more actual type dinosaurs on display than any other in the country. What you will see here are mainly the real bones, and not casts. This will have to change because of the gradual deterioration of the skeletons, so enjoy them while you can. You may be the last generation that will see real skeletal material on display.

Look at the map on the brochure. Note that the hall labeled Dinosaurs has a main entrance to the right of the elephant on the first floor map. Enter through this main entrance. [If you are interested, later you can walk into the small room labeled early life and watch the demos of how life might have begun.] As you enter the Dinosaur hall you will see a time line on a column in the center, a demo on how to become a fossil dinosaur on the left, and the dinosaurs in front of you.

Turn right up the ramp and follow the conquest of land. Note some of the adaptations plants had to have, the sizes of some of the early plant fossils, and depictions of early vertebrates. This small area essentially covers the Devonian time period.

Follow the plant hall through the Carboniferous. Note that the plants at this time were the very large lycopods and sphenopsids, as well as the seed ferns and ferns. Some of the early trees were precursors to the gymnosperms, the trunk in the center is one of these. Note that these plants capitalized on secondary xylem growth for support. Look to the left wall and you will see more of the gymnosperm tree forms. However, most of the tall trees of the Paleozoic belonged to the lower vascular plant groups. The lycopods, again on your left side with a very large trunk base, grew from secondary cortex formation, the tree ferns utilized roots around stems, and the sphenopsids utilized large hollow piths with some secondary vascular tissues formed - look to the right wall to see these adaptations. Estimate the relative sizes of these "trees" within the forest.

Animals were probably not able to get much nutrition from the plants of the Paleozoic unless they were eating the reproductive plant parts. At the end of the Paleozoic plants you will see Eryops on the right beside the tree forms. Estimate the length of the head, the length of the body and width of the head.

Now move on into the Mesozoic time period. Note the cycad types of plants near the end on the right side. These had large, squat, fleshy trunks but they are covered with leaf bases. The leaf bases tend to be hard and quite spiny. Look at the reconstructions of the plants, and note that there were not many leaves per plant (How many leaves do you see?) and that the soft apex was also very protected. Also here are fossil conifer woods with their very large trunks, but remember these trunks were secondary xylem (wood). Contemplate the types of food that the dinosaurs had available. You will see reconstructions later in the dinosaur dioramas.

There is a small "bridge" ahead of you - walk to it and look at the Cretaceous dioramas. Note that the large trees are conifers mainly and that the flowering plants were shrubs in flooded stream bank areas. Then turn back into the Mesozoic plants, and turn right to go into the reptiles. Here you will see the stem reptiles in the middle in a glass case.

Look to the right wall, "Early Reptiles" (the sailfin reptiles). Compare the skulls and stances of the two sailfins you see here with Eryops.

As you look at these sailfins, behind you in a glass case are the herbivorous early reptiles - dicynodonts, etc. Look at the dentition.

Finally go forward to the "What is a dinosaur" display and make note of characteristics. Compare this list with the list we gave you and note any differences.

Turn left to enter the main part of the dinosaur hall, noting the diorama of the Upper Triassic on your right. This portrays ALL the animals from all parts of the world and across the complete time period. However, the plants are taken only from the western United States during the Carnian. Most of the dioramas in this hall were done in the 1960s. What do you note about the reconstructions of the dinosaurs that indicate they were done during this time?

Go on into the hall and do the same for the Jurassic diorama on your right.

This one is mainly western US Morrison Formation (approximately Callovian), thus there is not as much mixing of animals as in the other dioramas.

Look at the dinosaurs in the central display of the hall. Begin with Allosaurus. Pay attention to the scapula, skull and tail. These will come up later. Examine the belly bones (gastralia) and see that this beast had a girdle. This allows the carnivore to eat large quantities of food at one sitting, hold it within the stomach while on the move without busting a gut, and digest over time.

Stegosaurus is the next skeleton beside you and there is a reconstructed one behind you. Compare number of bumps, hooks and grooves on the femur and ilium of the Stegosaurus and Allosaurus. More bumps and grooves indicate bigger and/or more muscles. Which of these two genera had a larger and more elaborate muscle system in the upper leg?

Note that in the Stegosaurus there were more muscles associated with the tail (see knobs and bumps again) than with the leg. The skeleton you are looking at here is unusual for this particular collection, because it is a composite of 50 different skeletons. Look at the plates and count the number present. Stegosaurs normally have 17 plates and clearly there are extra here in this skeletal reconstruction. Now look at the model Stegosaur next to the wall. This model was build in the 1930s for a World Fair display. Count the plates. This is only one aspect of the model that dates it. Look down under the fern in front of you. What reptilian lineage is represented by the animal lurking under the fern?

The next skeleton in the middle is Camarosaurus. You will also see its skull here with a skull of the large Diplodocus in the middle of the skeletons. These two genera existed during the same time period at the same place (coeval). Based on teeth and form of skull, do you think they competed for a food source?

Note the Camarosaurus and the position of the head and neck. This is a taphonomic phenomenon and should never appear in reconstructions. It occurs because of the differential drying of the nuchal ligament.

Now move to the front of the Diplodocus skeleton, and partly down the other side. Here look for the extremely large appendages compared to the central body portion. As a matter of comparison this central body portion is not much different from the elephant in the main rotunda. Look at the structure of the vertebrae in the neck. Look at the curvature of the complete tail. At the point where the curvature changes direction, there are four fused vertebrae which probably gave the tail a solid base for a tip that could whip about. This is difficult to see, but try.

Turn to the left and look at the Triceratops. Note the stance on the front versus the back legs. If you were to straighten the front leg (give it an upright position) would the articulation at the elbow fit together and support the front of the animal?

Note the large frill which probably serves many functions in this animal. One of them is the attachment of the very large jaw muscles, making this beast a powerful chewer.

Compare the skull of Triceratops with the mounted skull just behind it. One of these is a Centrosaurinae and the other is a Chasmosaurinae. Which is which?

Note particularly the nose septum and the horns.

The specimen labeled Brachyceratops is now considered to be a baby Styracosaurus. Note that the frill develops early but the ornamentation does not - it develops at sexual maturity. Likewise Monoclonius is now considered to be a growth stage of Centrosaurus.

On the wall is a small Heterodontosaurus which is one of the oldest dinosaurs from the Late Triassic. Look at the canine-like teeth in the mouth of this specimen.

Next on the wall is a Thescelosaurus neglectus skeleton. It has this specific name, and is a type specimen, because it was put into storage without study for years "neglected" until Gilmore found it in the basement and discovered it was a new species. This is probably a juvenile which has a blunt snout - a juvenile character of all dinosaurs except the oviraptors.

Next is a series of bone material from the euornithopod lineage. Note the specimens showing the dental battery with the three rows of interlocked teeth. Remember this occlusive type of dentition makes these the only dinosaur group capable of grinding up their food. Now look at the ossified tail tendons on the fossil on the wall. How does this tail structure compare with that you saw in the Allosaurus across the display?

The complete skull you see next is Edmontosaurus. Note how the teeth are inset from the margins of the jaw. Remember that this is a plurokinetic skull which allows the grinding motion of the dentition.

Finally we have reached the cast of a medium sized Tyrannosaurus rex. When you look at the row of teeth, compare the evenness of the teeth with those of the Edmontosaurus skull. What does this indicate about the process of tooth replacement in these two dinosaurs?

Note the very large multiple foramina in the skull. These are for the attachment of multiple, very large jaw muscles giving this animal maximum power for biting. Compare the size of this skull and the teeth with that of Allosaurus across the hall.

Next along the wall is the most prized specimen in the whole collection. This is the only reasonably complete skeleton of Ceratosaurus in the world and is the type specimen. However, the pubic bone on this skeleton is a cast (not the original), and the boot shape is probably incorrect. The actual shape should be more like a club.

You are now at the "11th Hour" diorama (1960s). Again the animals are cluster together into a great Late Cretaceous smorgasbord of forms from all over the world with some questionable reconstructions. For example, look at the Edmontosaurus body with the Anatotitan head.

Turn back to the central display and look at the Stegosaurus excavation. This is another type specimen on display and was the most complete skeleton known until 1993, when a new one was found by the Denver Museum paleontologists.

Look across to the Allosaurus skeleton on the other side of the hall. Note the scapula on this side of the animal. Compare with the left side you saw earlier, comment on the difference and tell us which one has suffered a break and regrowth of bone.

Note the Maiasaur and the eggs and move down to Camptosaurus. These two specimens were described as different species and are both type specimens. However, they represent an adult and a juvenile form. Observe the ilium on the adult. Do you notice any unusual feature (pathology) on the adult not present on the juvenile?

Note the position in this hall of the Camptosaurus, Allosaurus, Stegosaurus. Now walk up the stairs under the pterodactyl hanging from the ceiling. Up here are displays on living fossils and flight. Walk around to the balcony area so that you can view the skeletons you just noted below. Note whether the legs of these three genera, front and back, are sprawled or upright. Secondly compare the width of the pelvic area. Allosaurus could probably run faster in a straight line, but Camptosaurus was more maneuverable. Walk around the balcony and face the specimens mounted on the wall across from you. This will give you an overall impression of their size.

Once you are finished here, go back down the stairs, walk around the back where there is a display on excavating dinosaurs, and down into the ancient seas hall. Look at the Pleisiosaurs, Ichthyosaurs and other marine reptiles as you pass through.

Exit this hall back into the main rotunda, turn around the corner to the right and go up the stairs. Walk across the rotunda and into the bone hall. Items you should look at here are the giraffe and ostrich neck and compare the vertebrae to those in Diplodocus. What features of the neck vertebrae are similar in the giraffe, ostrich and Diplodocus?

Note the display on tooth structure for herbivore versus carnivore.

Examine the running birds paying attention to the pelvis, leg bones and feet; in particular compare the bones of the feet and ankle in these birds with those of Allosaurus.

In the area describing bone function and development, take a moment to examine some of the features adapted to function.

Study the crocodilian skeleton noting the pelvis and the sprawling stance.

Now as you turn around and leave this hall, note many convergent features of the mammal skeletal structure with that seen in the dinosaurs. You do not have to list particulars here, just get an overview, e.g. herbivore skull vs. carnivore skull, leg bones of fast and slow moving animals, etc.