Signs of severe dehydration in an infant include all of the following, EXCEPT:

In an infant, bulging fontanelles are not a sign of severe dehydration. In fact, bulging fontanelles can indicate increased intracranial pressure or other conditions rather than dehydration. The soft spots on an infant's head, or fontanelles, will typically appear sunken if the infant is dehydrated, which is a more reliable indicator of fluid loss.

On the other hand, profound tachycardia, delayed capillary refill, and dry mucous membranes are all classic signs of severe dehydration. Profound tachycardia indicates that the heart rate increases as the body attempts to maintain adequate blood flow in response to lower blood volume. Delayed capillary refill suggests poor peripheral perfusion, which can result from reduced blood volume. Dry mucous membranes indicate insufficient fluid levels in the body's tissues, further signifying dehydration. These signs are critical in assessing an infant's hydration status, while bulging fontanelles serve a different diagnostic purpose.