Question

1. count the growth rings on one of the costal scales (identified in fig. 21.4) on your specimen and estimate the turtles age.
2. how many toes are present on the forelimbs? on the hind limbs? how does this compare to amphibians? to mammals?
3. what external features of the turtle are homologous in mammals?

Explanation:

1. To estimate the turtle's age, count the growth rings on a costal scale as each ring typically represents one year of growth.
2. Turtles usually have 3 - 5 toes on forelimbs and hind - limbs. Amphibians can vary widely in toe number, some having none (e.g., caecilians) and others having 4 - 5. Mammals also vary, with some having claws or hooves instead of distinct toes, but many have 4 - 5 digits on each limb.
3. External features of turtles that are homologous to mammals include the presence of a head with sensory organs (eyes, nose, etc.) as both have these for perception in their environment.

Answer:

1. Count growth rings on costal scale to estimate age.
2. Turtles usually have 3 - 5 toes on forelimbs and hind - limbs. Amphibians vary in toe number; mammals also vary with many having 4 - 5 digits.
3. Head with sensory organs is a homologous external feature.