: But even then, the difference is in the overall proportions (the Great Dane's
: skull is very wolf-like, while the pug's has a reduced snout/flatter face,
: larger eye sockets, and is much smaller overall). While it does show how
: much variation can be produced within a species, it's still totally
: artificial. In nature, there is very little morphological difference
: between subspecies of a given species. The natural subspecies of Canis
: lupus are all largely indistinguishable from each other. Same for the
: various tiger subspecies (e.g., Bengal, Sumatran, Siberian). The untrained
: eye would be unable to tell them apart.

Speaking of the pug's skull. It's overall morphology has many features indicative of what is called neoteny or paedomorphism, the retention of juvenile features into adulthood. The Wiki articles on lap dogs and the origins of the domestic dog and this blog post mention breeding dogs that retained neotenized or "cute" features like small size, reduced snout, flatter face, bigger eyes in relation to the head, and so on, as well as neotenized behaviors (being more sociable and docile like young grey wolves). Just look at how cute this grey wolf puppy is:

And here's what's supposedly the skeleton of a newborn wolf being shown in a museum or exhibit of some kind:

Just compare that with the wolf and dog skulls in my previous post.

: You have to go up to the taxonomic level of family to get differences in
: morphology and skeletal structure between member species of the same
: taxon.

That should read "to get significant differences."