A small, lens-shaped radial sesamoid embedded into the APL tendon is a primitive state found in all known Carnivora genera except in the red and giant pandas and the extinct Simocyon where it is hypertrophied (enlarged) into a sixth digit or a so called "false thumb", a derived trait that first appeared in ursids.
Recently, scientists at the Royal Veterinary College in the United Kingdom have discovered that the elephant possesses a sixth false toe — a sesamoid, located similarly to the giant panda's extra "thumb".
Out of racing for a time due to an injury, Placid Ark came back in 1988 to win the Bobby Lewis Quality before a shattered sesamoid resulted in the gelding having to be euthanized.