THIS PARTICULAR set of dino-facts is based upon work done by Jack Horner and other associates of The Museum of the Rockies in Bozeman, Montana. The data has been used in order to theorize about the behavior of dinosaurs in that area.

Students should have some working knowledge about the three dinosaurs mentioned before beginning this activity. It is sufficient for them to know that several different dinosaurs lived at the same time (roughly 80 million years ago) in this vicinity. Three of these dinosaurs were Orodromeus (mountain runner) which was a swift plant eater; Troödon (wounding teeth) which was a small but fierce predator (carnivore); and Maiasaura (good mother lizard), a larger herbivore. There is good fossil evidence to show that all three laid eggs in nests. The environment at that time included volcanoes and a few mountains to the west (not the Rockies as they were in the process of uplifting) and to the east, a warm interior seaway which divided North America from north to south. The nesting sites included two islands surrounded by a shallow alkaline lake

Objectives: Students will gain an understanding of paleontological field work. Students will analyze evidence gathered by paleontologists. Students will work cooperatively to develop and support their own hypotheses about dinosaur behavior based upon the dino-facts. In learning more about dinosaur behavior, students will also gain an understanding of the processes involved in making hypotheses about past events in earth's history.


Duplicate the "Dino-Fact" section below. Cut out and laminate each card and place in an envelope. Make one set of "Dino-Facts" for each group of students.


1) Distribute an envelope containing a set of "Dino-Facts" to each group of students.
2) Students should remove the facts and arrange them so that everyone in the group can see them. Read through each card with the students to make certain that the terms and content of each "Dino-Fact" are understood.
3) Students are to discuss the facts quietly within their groups. By grouping various facts together, students should develop at least one hypothesis about dinosaur behavior. Ideas will be written on paper and then presented to the rest of the class with an explanation of the support of each hypothesis. (Multiple hypotheses are certainly to be encouraged!)
Example: Clue #1 states that maiasaurs probably ate nearly 200 lb. of vegetation each day. Clue #11 states that they have been found in herds up to 10,000 in number. A class discussion around these two facts might result in a theory such as:
The maiasaurs must have migrated because they would need to find new food sources.
Use other examples only if necessary.
4) Allow sufficient group discussion time and offer guidance only when necessary.
5) Students will then present their hypotheses to the rest of the class.
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1) Read Maia: A Dinosaur Grows Up by Jack Horner and James Gorman. Have students make note of the comparison of their own hypotheses with those presented in the book.
2) Have students note the use of modern birds in the "Dino-Facts." Comparison to living organisms is a useful tool for scientist working with the past. Can students think of other examples?
3) Can students think of any possible experiments to test any of their hypotheses? (Relate to #2 here. A possibility would be to consider herds of large herbivorous animals today. Do they migrate?)


#1) Maiasaurs were herbivorous. Adults weighed roughly 3-4 tons. They probably ate about 200 lb. of food each day.

#2) Many Maiasaura nests have been found at two sites, Egg Mountain and Egg Island. At the time of the dinosaurs, each of these sites was an island. Although islands are rather limiting in space, the nests are usually found 25-30 feet apart.

#3) The sharp serrated teeth of a small dinosaur called Troödon have been found in the nesting areas of maiasaurs.

#4) Large numbers of bones found at one location in Montana indicate that there existed a herd of maiasaurs of nearly 10,000 individuals. These individuals varied in size from 9' to 25' in length.

#5) The dinosaur nests at both of the Egg Mountain locations have been found at three different depths. Several layers of sandstone were deposited between the nesting horizons.

#6) The bones of most newborn birds are not fully ossified (hardened into bone). The ends are still relatively soft and spongy and made of cartilage. As a result, newborn birds can stand up only momentarily. Their bones will not support them.

#7) An adult Maiasaura reached a size of 25-30 feet in length. It weighed 3-4 tons.

#8) The shells found in the nests of the Maiasaura are all broken up.

#9) The front teeth of many dinosaurs like Maiasaura are very interesting. There is a heavy enamel layer on the outside of the upper teeth, but that very same layer is on the inside of the lower teeth. Therefore as the teeth come together, a self-sharpening effect takes place. The teeth become like chisels.

#10) The shells found in the nests of Orodromeus are not all broken up. The lower egg shell is usually intact.

#11) The presence of large numbers of bones at one site suggest that maiasaurs were found in herds up to 10,000 in number.

#12) The bones of the hatchlings of Maiasaura are not fully ossified. The ends are still relatively soft and spongy and cartilaginous.

#13) Examination of the embryos of Maiasaura show wear on the front teeth. This has occurred before hatching.

#14) At birth, maiasaurs are about 12 inches in length. Bones have been found in the nests of maiasaurs that were over 3 feet in length. This is very common.

#15) The bones of the hatchlings of Orodromeus are fully ossified. That means that the ends of the bones are fully developed and very strong.
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