The expected growth mark marker for a 6 month old infant is that the infant can transfer objects from hand to hand, rolls from prone to supine, sits well unsupported, presents with stranger anxiety, and that the patient can babble.
It is called the Rugae.
Rugae is a term used in anatomy to refer to a series of ridges produced by folding of the wall of an organ. For example the gastric rugae which allows for expansion of the stomach after the consumption of foods and drinks. The rugae of the vagina are the transverse ridges on the mucous membrane lining the vagina. They allow the vagina to stretch during childbirth.
An air mass bringing dry, frigid winds to North Dakota
Organs or skeletal elements of animals and organisms