ANSWERS

Unit 7: Link and Think

1. Order Xenarthra (formerly Edentata); sloths

2. The answers follow; check out the World Wide Web to see pictures of giant sloths and a glyptodont, both extinct xenarthrans.

	Pangolin	Anteater	Armadillo	Two- and three-toed _____
Any teeth?	no	no	yes	yes
Body armor?	yes	no	yes	no
Claws?	yes	yes	yes	yes
Long tongue?	yes	yes	no	no
Eats insects?	yes	yes	yes	no
Xenarthrous processes on lumbar vertebrae?	no	yes	yes	yes
Native countries	Africa and Asia	Americas	Americas	Americas

3. Like the pangolin and anteater, it has long claws good for digging, has a long tongue, and eats insects; it belongs to Order Tubulidentata.

4. It is a lagomorph. Lagomorphs are distinguished from the other two by the enamel on both the front and back surfaces of the tooth (lip and tongue sides) and by the second pair of top molars. Rodents and hyraxes only have enamel on the lip side of their incisors; also, they only have one pair of upper incisors, not two like the lagomorphs. Note about dental formulas: Dental formulas describe four sets of teeth: the incisors, canines, premolars, and molars. What look like four fractions are really the number of uppers over the number of lowers for each type of tooth. The numbers only describe the teeth for one side of the skull. The guinea pig formula is 1/1, 0/0, 1/1, 3/2; from this we gather that they have no canines (0/0) and have three upper molars and two lower molars on each side of the face (3/2). The total number of teeth for a guinea pig is (1 + 1 + 0 + 0 + 1 +1 + 3 + 2) X 2 = 18

5. Elephants and sirenians