What morphological feature serves as the quickest identifier separating the Cardigan Welsh Corgi from the Pembroke?

The Cardigan has a long, fox-like tail

The most striking physical marker used for the immediate differentiation between the Cardigan Welsh Corgi and the Pembroke Welsh Corgi involves the tail structure. The Cardigan is characterized by possessing a full, long tail, often described as a fox-like tail or a brush tail. Conversely, the Pembroke Welsh Corgi is often naturally born with a shortened tail or has historically had its tail docked to conform to established breed standards, resulting in a short or absent tail. This clear morphological difference, maintained through generations, is substantial enough to solidify their standing as two distinct, separate entries in official classification systems for recognized dog breeds, despite sharing ancestral lineage in Wales.