Brooklyn College
City University of New York

FIELD TRIP GUIDE APPENDIX

Page 7

HALL OF VERTEBRATE ORIGINS: Proceed back to the Hall of Saurischian Dinosaurs. Walk completely through it, and exit through the archway at the rear of the hall into the Hall of Vertebrate Origins (use map of 4th floor if necessary).

1. PTEROSAUR: Hanging from the ceiling is a skeleton of a pterosaur, a flying reptile of the Mesozoic Era (but not a dinosaur). Sketch one of the wings. Which finger forms the main support for the wing surface?

2. MOSASAUR & PLESIOSAUR: Proceed through the Hall of Vertebrate Origins. Notice the skeletons of the mosasaur and plesiosaur (hanging from ceiling) - two reptiles (but not dinosaurs) common in deposits of the Western Interior Seaway described during the first class meeting of the semester. What evidence can you cite that demonstrates that both of these animals were aquatic rather than land-dwelling?

HALL OF PRIMITIVE MAMMALS: Proceed to the Hall of Primitive Mammals, using the map of the 4th floor if necessary. Find the skeletons of Dimetrodon and Lycaenops. Both are members of the Synapsids, or mammal-like, reptiles - the reptile group from which mammals evolved in the late Triassic Period. They also are not dinosaurs. Mixed in with their obvious reptilian look, Synapsids have a variety of typically mammalian features. They are a curious amalgam of reptile and mammal.

1. DIMETRODON: Dimetrodon is an example of what are called "Pelycosaurs", i.e. "primitive" members of the mammal-like reptiles. They are primitive in the sense that they have few mammalian characteristics. What mammalian features, if any, can you see in this animal? If you are not sure (and there is no reason you should be since we haven't discussed these animals in class) look closely at the teeth. Are they all exactly the same shape? Are your teeth all exactly the same shape? (You are a mammal.)

2. LYCAENOPS: is an example of what are called "Therapsids", i.e. "advanced" members of the mammal-like reptiles. They are advanced in the sense that they possess a fairly large number of mammalian characteristics. They are the direct ancestors of mammals. Observe the body. It has a dog-like look to it, don't you think? (Dogs are mammals). Examine the teeth. Notice the enlarged, dog-like canine teeth. Do carnivorous reptiles (e.g. dinosaurs) have enlarged canines? Do carnivorous mammals (e.g. dogs & cats) have enlarged canines? Finally, you might ponder why, with all its mammalian features Lycaenops is still a reptile. The answer is in the jaw. Can you come up with an explanation?