Dr. digger, a paleontologist, finds a fossil that he describes in his journal. the creature was approximately 1 meter long, with its backbone fused into a large shell covering the body cavity. it had a beaklike mouth, without teeth, and all four limbs were in the form of flippers. based on anatomical similarities, to which modern animal is dr. digger’s creature most closely related?

The answer is a sea turtle.

The creature had a backbone, so it must be vertebrate. Among the vertebrates, there are no infinitive number of animals with shells. It could be only turtles. The characteristic such as a beaklike mouth without teeth supports a surmise. Limbs in the form of flippers suggest that animal must live in the water, and with such a dimensions it could live only in seas. All of these speak for the sea turtle fossil.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.