Between these a V-shaped ridge extending proximally serves for the insertion of the flexor pollicis longus.

The phalangeal formula in the flippers of cetaceans (marine mammals) varies widely due to hyperphalangy (the increase in number of phalanx bones in the digits).

[14] In vertebrates, proximal phalanges have a similar placement in the corresponding limbs, be they paw, wing or fin.

The distal phalanges are cone-shaped in most mammals, including most primates, but relatively wide and flat in humans.

The morphology of the distal phalanges of human thumbs closely reflects an adaptation for a refined precision grip with pad-to-pad contact.

[12] In Neanderthals, the apical tufts were expanded and more robust than in modern and early upper Paleolithic humans.

A proposal that Neanderthal distal phalanges was an adaptation to colder climate (than in Africa) is not supported by a recent comparison showing that in hominins, cold-adapted populations possessed smaller apical tufts than do warm-adapted populations.

[15] In non-human, living primates the apical tufts vary in size, but they are never larger than in humans.

Enlarged apical tufts, to the extent they actually reflect expanded digital pulps, may have played a significant role in enhancing friction between the hand and held objects during Neolithic toolmaking.

[11] Among non-human primates phylogenesis and style of locomotion appear to play a role in apical tuft size.

Suspensory primates and New World monkeys have the smallest apical tufts, while terrestrial quadrupeds and Strepsirrhines have the largest.

[18] The evolutionary process continued over time, and a very derived form of hyperphalangy, with six or more phalanges per digit, evolved convergently in rorqual whales and oceanic dolphins, and was likely associated with another wave of signaling within the interdigital tissues.

[19] In ungulates (hoofed mammals) the forelimb is optimized for speed and endurance by a combination of length of stride and rapid step; the proximal forelimb segments are short with large muscles, while the distal segments are elongated with less musculature.

The giraffe, the largest even-toed ungulate, has large terminal phalanges and fused metacarpal bones able to absorb the stress from running.

[20] The sloth spends its life hanging upside-down from branches, and has highly specialized third and fourth digits for the purpose.

The arboreal specialization of these terminal phalanges makes it impossible for the sloth to walk on the ground where the animal has to drag its body with its claws.