Step 1: Recall heart chambers in vertebrates.
The number of heart chambers changes across vertebrate classes. Fish have two, most reptiles have three, and birds and mammals have four.
Step 2: Check Pteropus.
Pteropus is the fruit bat, a mammal. Mammals have a four-chambered heart, so this does not fit.
Step 3: Check Scoliodon and Hippocampus.
Scoliodon is the dogfish shark and Hippocampus is the seahorse. Both are fishes, so each has a two-chambered heart. Neither fits.
Step 4: Check Chelone.
Chelone is a marine turtle, a reptile. Most reptiles have a three-chambered heart, with two atria and one partly divided ventricle. This fits.
Step 5: Confirm the reptile feature.
The turtle's heart is three-chambered, which is the typical reptilian pattern, even though the ventricle is partly split.
Step 6: State the answer.
The animal with a three-chambered heart is Chelone.
\[ \boxed{\text{Chelone}} \]