Step 1: Check Statement I.
Gigantopithecus was a giant ape (extinct) from the Miocene–Pleistocene of Asia. It belongs to the family Hominidae, subfamily Ponginae (closely related to orangutans).
Thus, Statement I is correct.
Step 2: Check Statement II.
Equus is a living genus including horses, donkeys, and zebras, and is the only surviving genus of the family Equidae.
Thus, Statement II is correct.
Step 3: Check Statement III.
Gomphotherium is an extinct proboscidean (order Proboscidea), related to elephants, with long lower jaws and shovel-like tusks.
Thus, Statement III is correct.
Step 4: Conclusion.
All three statements (I, II, III) are correct.
Final Answer:
\[
\boxed{\text{(D) Statements I, II and III are correct.}}
\]
| Group I | Group II |
| P. Dissepiment | 1. Echinodermata |
| Q. Delthyrium | 2. Trilobita |
| R. Pygidium | 3. Brachiopoda |
| S. Ambulacrum | 4. Anthozoa |