If born from a natural birth, a small gallifreyan at birth has a tail, an evolutionary residue that is reabsorbed with age.
The dark line in the front of the eyes is a typical indicator of childhood and adolescence (generally this period ranges from birth to 24 years, but it's different according to the amount of temporal radiation absorbed by the body during growth. In fact the timelords have childhoods and adolescences that can last even more than 50 years).
The spots in the shoulders, in the legs and in the back begin to see after a few months from birth (or creation in a loom). The greater the age, the greater will be the presence of stains in the body and the size of them.
The arm in the adult is transparent so we can see the back and the size of it.
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(Sorry if the speech is a little weird, English isn't my mother tongue)