Find the Coelocanth, an ancient fish with extant (living) descendants. 

1. Where are the descendants found today?:  

Off the coast of Africa and in Indonesia

2. Examine the fish specimens mounted on the wall behind the Coelocanth.  What do you notice about the tail configuration of the fossil fish from Green River and that of the Coelocanth?  

They have a 3-lobed tail, they are extraordinarily similar (almost identical) and they are thick and a vertebrae can be seen running through the tail.

3. Compare the pectoral fin supports for these fish with that for the Coelocanth.  How do they differ?

They differ in that one of the pectoral fins is more paddle like and extraordinarily thick. While the other is more “arm like” and seems to be slightly thinner.

4. Early bony fishes had what kind of covering? (look up on the wall)  What happens to the scales with later day bony fishes?

They had large and thick scale coverings, and as they evolved they changed to become smaller and thinner.

1. Find the 42-foot long skeleton of Kronosaurus, a marine dinosaur in ROMER HALL.  How many “fingers” are there in its paddle-like front fin?: Five “finges”

2. What is the primitive (most ancient) phalangeal formula for reptiles?  (HINT:  look at some of the other reptile skeletons in the room and note that our phalangeal formula is 2-3-3-3-3 or 2 for the thumb and 3 for all other fingers.): 3-3-3

3. What is the formula for Kronosaurus? : 3-3-3-3-3

4. What has happened to the phalangeal formula?  (This is known as “hyperphalangy”.) : It has removed the “thumb” and increased

5. What would be the advantage of the condition of hyperphalangy?

The advantage of hyperphalangy is that it allows for the creation of a paddle-like “hand” proving advantageous for marine organism because as it is moving through its environment it can move fast and efficiently.

6. Do you see evidence of hyperphalangy in other reptiles in the room?  If so, list them.: Mystriosarus, Diadectos, Adaphosaurus

7. Can you find other examples of hyperphalangy in the museum? What are they?: Whales

8. How do you think that hyperphalangy arises?  (HINT:  remember back to the comparison with the number of thoracic vertebrate in a chick versus a snake and how that was caused.)

Hyperphalangy arises because it is an adapatation to the organims enviornemnt. It not only provides an advantage (in the case of the Kronpsaurus) but it allows the organims to better interact with the enviornment. Suiting their individual needs for survival. It also, in this case, will help the animal swim better. 

9. Where are the external nares located on Kronosaurus?

They are located directly under the eye sockets on the head of the Kronosaurus. 

10. Compare this position to where the nostrils are located on other reptiles? Why do you think they are located in this position?

Other reptiles have their nares located under the eye sockets in the skull. I think the Kronosaurus has them located their as well because it is a marine creature that breaths air, and it is needed so it can stick its head above water and breath air as efficiently and easily as possible.

11. Do you see this alteration in position of external nares in any other group elsewhere in the museum?

Yes, another group that I saw, which was located in the great mammal hall, was the whale that was hanging from the ceiling.

12. Are these similarities between phytosaurs (Kronosaurus) and the other group due to recent common ancestry or to similar ecologies?  What is the evidence for your answer?

They are similar because of similar ecologies. Both are marine organisms living under water. They also both breath air and both have hypophalanges. The similar environments and then the fact that they both breathe is what makes them so similar, they both require the same adaptation to best survive in their environment.