**Core Concept**
Scaphocephaly is a congenital condition characterized by an elongated skull shape, resulting from premature closure of a specific cranial suture. This premature closure leads to an abnormal skull growth pattern, causing the skull to become narrower and longer.

**Why the Correct Answer is Right**
The premature closure of the sagittal suture is responsible for scaphocephaly. The sagittal suture is a fibrous joint that separates the two parietal bones in the skull. Normally, it remains open until the late teenage years or early twenties. However, premature closure of this suture can occur due to various factors, such as genetic conditions, trauma, or abnormal growth patterns. As a result, the skull grows more rapidly in the anterior-posterior direction, leading to the characteristic scaphocephalic shape.

**Why Each Wrong Option is Incorrect**
**Option A:** Premature closure of the coronal suture can lead to brachycephaly, characterized by a short, broad skull shape. This is not associated with scaphocephaly.
**Option B:** Premature closure of the lambdoid suture is not typically associated with scaphocephaly, and may lead to other cranial deformities.
**Option C:** Premature closure of the metopic suture can lead to trigonocephaly, characterized by a triangular forehead shape. This is not associated with scaphocephaly.

**Clinical Pearl / High-Yield Fact**
Remember that scaphocephaly is often associated with craniosynostosis, a condition where one or more of the cranial sutures close prematurely, leading to abnormal skull growth and potentially increased intracranial pressure.

**Correct Answer:** D. Sagittal suture