It is just a foot

The Purpose of Cat Feet in Dogs Cat feet are known to help dogs with endurance. Indeed, according to research conducted by Christine Zink in 2020, cat feet are seen in dogs selectively bred to move effortlessly over rocky or uneven ground.
 Zink has compared cat-footed dogs with the knobby tires of an ATV meant for improving grip on uneven surfaces.
It's therefore not a coincidence that many dog breeds blessed with cat feet were selectively bred for agility in moving in all directions or over rough ground.
Being round and with short third digital bones, these paws require less energy to lift off the ground. 
The perfect example of a cat-footed dog is the Afghan hound, a breed that was selectively bred to hunt prey over rocky ground.
However, not all cat feet in dogs are desirable. Depending on the breed, cat feet may be a highly desirable trait or a major fault.

​References
Dog Discoveries,https://dogdiscoveries.com/curiosity/discovering-cat-feet-in-dogs

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