Members of the cat family – including domestic cats and wild cats like the lion – have dewclaws. Generally a dewclaw grows on the inside of each front leg but not on either hind leg.
The dewclaw on some cats is not vestigial. Wild felids use the dewclaw in hunting, where it provides an additional claw with which to catch and hold prey. The dewclaw may not be used by domestic cats, however, and pet owners should trim their cat's dewclaws regularly so they do not curve into the vestigal pad.
↑ 1.01.1Clipping a Cat's Claws (Toenails). Pet Health Topics. Washington State University College of Veterinary Medicine (22 July 2009). Retrieved on 2 November 2013. “Cats have a nail on the inner side of each foot called the dew claw. Remember to trim these as they are not worn down when the cat scratches and can grow in a circle, growing into the foot.”
↑ 2.02.1Physiology. Lion ALERT. Retrieved on 2 November 2013. “Lions have four claws on their back feet but five on the front where the dew claw is found. This acts like a thumb and is used to hold down prey while the jaws rip away the meat from bone. Set well back from the other claws the dew claw does not appear in the print.”