This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Which of the following is not present at bih? 
Select and explain. 
A. Mastoid tip, B. Mastoid antrum, C. Ethmoidal labrynth, D. Endolymphatic sinus
A: Mastoid tip
Answer: A: Mastoid tip 
Explanation: The mastoid process is absent or rudimentary in neonatal skull. It forms postnatally as sternocleidomastoid develops and pulls on the bone Web search