Humanoid, mammalian physiology with some small differences in the internal and external built.  For the internal, it goes mostly with vocals and digestive system, as well as metabolism too.  For the external, individuals of Highborns and Primatarians can grow physical features of their marked creature. While they cannot grow fur, they can grow wings, talons, claws, etc.. While most Highborns possess sharp jaws or bigger canines (depending on mark), some can even grow sabre teeth and extend their jaw gape to 90 degrees. For most of the modern day Highborns, these features are only accessible to them after they reach their prime or in other words become mature. 