For further information about dwarfism in donkeys please follow these links:

Love Long Ears. A miniature donkey website with silhouettes of visually identified dwarf donkeys. Also contains pages on measuring for disproportion and dwarfism identification.
http://www.lovelongears.com/sidebyside.html
http://www.lovelongears.com/silhouettes.html
http://www.lovelongears.com/dwarfmeasure1.html

Case Story Romeo. A story about a dwarf donkey named Romeo and the identification of his disorder.
http://www.lovelongears.com/dwarf_romeo.html

Some types of dwarfism can already be tested e. g. at UC Davies: https://www.vgl.ucdavis.edu/services/coatcolordexter.php

Dwarfism in "Deutscher Schäferhund, Saarloos Wolfshund, Tschechoslowakischer Wolfshund" can already be tested e. g. at Laboklin, Germany: http://www.laboklin.de/index.php?link=labogen/pages/html/de/erbkrankheiten/hund/hund_zwergenwuchs.htm

You are wondering about this little dwarf elephant? You can read more about him here: https://news.mongabay.com/2013/12/little-elephant-is-the-first-scientific-record-of-dwarfism-in-the-wild/