There are variety of dwarfisms and each can have its own genetics; the most common kind of dwarfism is Achondroplasia; these individuals have common facial features and patterns of limb shortening; the same gene mutation can occur in other species; Cocker Spaniels have this gene; they are essentially achondroplastic dwarfs.
Woops; Daucshounds not spaniels;
For the most part the other types of dwarfism are not encountered by the general public because they are excedinlgy rare and typically fatal (one type is literally called Thanatophoric Dwarfism)
I know something about dwarfs because I am a radiologist of a certain age; when I did my training back in the 70s there was no CT and certainly no MRI; mostly just plain radiographs (old fashioned xrays). Now there is not much you can see that is unique on plain radiographs but bones are certainly visible and most forms of dwarfism produce very specific patterns of bone abnormality. The first chapter of the basic resident text in Radiology was on bone and there were over 30 pages on all varieties of dwarfism; since I had virtually no experience in Radiology when I started this text I quickly became discouraged. But the chairman of my department was a bone radiologist and he loved complex rare diseases so he collected radiographs of dwarfs; Several times a month a Chairman of Radiology at Baby's Hospital in Manhattan would come to give us conference. My boss would always whip out some obscure dwarf film to try to fool him; for the most part the visiting professor was ! ! calm; he endured his occaisonal mistake with much dignitiy; but one day when shown a particularly severe case he sighed and said "Harold (my boss) there are only two kinds of dwarves; live one and dead ones (pause) this is a dead one.
