Dinosaurs under the big sky


Download 3.06 Mb.
Size3.06 Mb.
1   ...   5   6   7   8   9   10   11   12   ...   34


For many decades, scientists thought that birds and reptiles were distinct, unrelated groups of vertebrate animals because reptiles were thought to have all been cold-blooded and birds were known to be warm-blooded. This way of thinking was based on early classification systems, which used warm-bloodedness as a way of grouping animals and which did not take into consideration the idea that different groups of animals could be related because of evolution . Now that we understand extinction and evolution, we are better able to classify animals, and we realize that animals with the most shared characteristics are the most closely related to one another.
We now know that warm-blooded animals evolved from cold-blooded animals, and therefore warm- and cold-blooded animals can be in the same group. Birds share more characteristics with Dromaeosaurid and Troodontid dinosaurs (a group named Deinonychosauria), than with any other group of animals. Therefore, we can hypothesize that birds evolved from this group of dinosaurs. This means that birds are actually a group of reptiles, rather than a distinct

group unto themselves. Birds are living dinosaurs.

Until someone can demonstrate that another group of animals shares more characteristics with birds than do dinosaurs, the theory is considered to be strong, and therefore, scientifically true. Recent discovery of preserved protein in a Museum of the Rockies Tyrannosaurus rex provided strong, additional support for this theory . The T-rex protein is most similar to that of a modern bird.

Some of the important characteristics shared by some dinosaurs, and all birds include the following: 1. Furcula, or wishbone (MOR 1125B)

2. Hollow bones (MOR 1181B)

3. Extra-long digit of the hand (MOR 747R)

4. Oblong, hard-shelled eggs (MOR 702)

5. Semilunate carpal bone of the wrist, the bone that allows a bird wing to fold to

the side of the arm (MOR 747B)

6. Three-toed foot (MOR 747R)

7. Feathers

8. Egg brooding

Case Contents: Tyrannosaurus furcula (wishbone); Bambiraptor furcula;

Troodon egg; modern chicken skeleton;

Deinonychus left hand, semilunate carpal (wrist bone),

and right foot

Ornithominius hollow toe bone
NOTE: The Archaeopteryx is the earliest known bird. It lived 150 million years ago and is the only bird fossil known from the entire Jurassic Period. The original specimen was found in the mid-1800’s and is in the collection of the Berlin Museum of Natural History, Germany. Archaeopteryx gave scientists the first evidence of what the earliest birds were like. The fine-grained stone surrounding the body also preserved impressions of feathers. It was the first time feathers had been seen on a prehistoric animal. Archaeopteryx had sharp teeth, clawed fingers, and a long bony tail. Other than the feathers, Archaeopteryx was very similar to small theropod dinosaurs (How Dinosaurs Took Flight, pp. 8, 49).



In paleontology, articulated skeletons are specimens in which the bones remain in the positions they occupied during the animals’ life. A specimen needed to be quickly buried after death to remain articulated. Articulated skeletons are very important for studies of dinosaur locomotion, stance, and a variety of other activities; but unless they are completely dismantled, it is difficult to study individual bones. Disarticulated specimens, where the bones are apart or separated, are easier to collect from the field and allow for more thorough study of individual bones. For example, disarticulated skulls are the best skull specimens for research purposes.
The skulls of all vertebrate animals are made up of numerous individual bones, all of which function to contain various organs such as the brain, eyes, hearing apparatus, and mouth. In

humans and most other mammals, these separate bones fuse together tightly as an animal grows older. In many reptiles, including some dinosaurs, many of the bones remain separate, which allows the skull to be more flexible in life. When dinosaur skulls are found articulated (together) we can presume that the animal was either buried very quickly by sediment or that it was an old adult, and the bones were fused together. When we find skulls disarticulated (apart) it could mean that the skull was exposed to the weather for a period of time, or that it belonged to a juvenile.

Case Contents: In this case you see two casts of the best Tenontosaurus skull ever

discovered. It was found completely disarticulated, and the individual bones had suffered

only minor distortion during fossilization. The exploded skull to the right shows each of

the individual bones, while the articulated skull to the left shows how all the bones fit

together. Note: The skull of the “Catherine” Tyrannosaurus rex (B-rex) skeleton is another

example of a perfectly disarticulated skull. The 40+ skull pieces were exceptionally well-

preserved. The B-rex skull on display in the Hall of Horns and Teeth is a replica cast.

No, we don’t mean the BIG events 65 million years ago. We’re talking about the ordinary life and death of dinosaurs. What were some of the ways dinosaurs died and how do we know?
Taphonomy is the study of what happens to organic remains from the time the organism dies until its remains are found. Paleontologists use taphonomy to look for clues to what happened to the dinosaurs just before and just after their deaths such as evidence of predator or scavenger activity (See A Muddy Diplodocus Grave display) or pathologies and other abnormalities indicating diseases or injuries (See Allosaurus’ Tough Life display). (DBS, pp. 28-29)

Share with your friends:
1   ...   5   6   7   8   9   10   11   12   ...   34

The database is protected by copyright ©dentisty.org 2019
send message

    Main page