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In an alien world, due to changes in the ecosystem animals that were once mostly arboreal started having to spend more time in open plains, adapting to fill a new niche of grasslands/bush eaters and predators. The predator in question evolved from a creature with long, four- fingered limbs, employing knuckle walking on the ground to conserve its claws, which it used for climbing and taking down prey.

In this scenario, could a previously arboreal predator maintain its knuckle walking while becoming a predominantly cursorial predator? What changes would their front limbs suffer to allow this?

Additional information: The creature is roughly the size of a small spotted hyena and was originally a quadrupedal digitigrade, with limbs ending in structures similar to zygodactyl birds (2 opposable digits, slightly smaller than the two middle digits, with the middle ones being used for knuckle walking). Its prey was also originally adapted for arboreal life, and there were no other predators of prey already filling the new niches. In the new environment there are still trees, which it will climb for resting, like some modern day big cats. Its neck has 15 vertebrae and is flexible like an owl's, previously used to search for prey along with its sharp vision. The mandibles aren't used in active prey takedown. Its overall skeletal structure is similar to our world's due to coming from an similarly structured ancestor (yes, I know how unlikely that would be).

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    $\begingroup$ this depends on what you mean by cursorial, can it knuckle walk sure but it will not be fast. knuckle walking has evolved more than once, look up chalicothere. but if it has zygodactyl hands what it does will not be identical to knuckle walking anyway. you might be better off with it walking normally on one set of toes and using the others for climbing. $\endgroup$
    – John
    Apr 13, 2020 at 13:46
  • $\begingroup$ The marsupial lion Thylacoleo is in several ways like what you describe - an arboreal creature which kept it claws on transitioning to carnivory, and used them (with a koala-like grip) to dispatch prey. I thought maybe it was a knuckle walker - but it was plantigrade, with retractile claws. tandfonline.com/doi/abs/10.1671/039.029.0424 $\endgroup$
    – Willk
    Apr 13, 2020 at 15:35
  • $\begingroup$ sounds terrifying youtu.be/n7gcats5uCQ $\endgroup$
    – Ewan
    May 14, 2020 at 12:46
  • $\begingroup$ @Ewan it does, though I envision mine to be something more in between a chimpanzee and a leopard $\endgroup$
    – ProjectApex
    May 14, 2020 at 14:44

2 Answers 2

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In order to become cursorial, the knuckles would have to become more hoof-like, and the bones above the knuckles would thicken and extend to support the animal's weight

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It is possible, but the creature's "hands" would need to evolve towards hoofs or something similar. The middle two "fingers" would evolve to become strong enough to support the animal's weight for faster walking. The joints of the middle two "fingers" would have limited mobility and would only be able to hook onto trees for climbing.

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