GEL 113 Homework 11 Answer sheet

Study Questions for Chapter 17: Reptilian Synapsids

Part I: True or False:

1.T 2.F 3.F 4.F 5.F 6.T

Part II: Multiple Choice:

1.B 2.C 3.C 4.B 5.D 6.A

Part III: Thought Questions:

1. Synapsids are a clade of animals which includes some ancient reptiles and all mammals. Mammals are living representatives of the synapsids.

2. a) The most likely primary function of the pelycosaur sail was thermoregulation - helping the animal warm up by absorbing solar heat, and also cool down by shedding heat like a radiator.

b) Evidence for a thermoregulatory role for the sail consists of experiments using a water filled drum about the size of a pelycosaur, which showed that the presence of a sail increases the rate at which it warms up.

c) Another possible function of the sail would be for display, either in mating or defense (scare away potential predators).

3. The evidence for endothermy in therapsids is circumstantial. They lived in high temperate regions so they must have been able to withstand cold temperatures. Some had a lumber region which would suggest the presence of a diaphragm which suggests a higher metabolic rate (greater volume of air taken in with each breath). Their bones do not show growth rings, but instead are highly vascularized which is most common in endothermic animals. They show some indication of having had whiskers, which would suggest that they may have had hair (insulation). Some fossil therapsids have been found at the bottom of burrows, curled up in a fashion similar to that of cats and dogs which is used for heat retention.

4. Dicynodonts were herbivores. They had tusks for pulling up roots and sharp beaks for slicing up vegetation. They were an important part of the Late Permian and Triassic terrestrial ecosystem because they served as a food source for carnivorous archosaurs, protomammals and eventually early dinosaurs.