First of all, having been stung recently, I’d like to distinguish between transitional fossils and intermediate fossils. The number of true transitionals is small, and although this partly reflects the very nature of cladistics (nothing is ever assumed to descend from a known type, but shares a common ancestor, which is always a hypothetical node on the cladogram, not a species), it matters as soon as you move away from gradualism.
Zeno’s paradox does depend on the infinite division of a change, and so is most relevant to Darwinian gradualism - if the paradox were valid, then gradualism would be impossible in principle - but fortunately, the number of genes that can change is finite, and so the paradox doesn’t apply even there.
But the philosophical resolution of the paradox was achieved in ancient times by Aristotelian metaphysics, by saying that each of those infinite divisions was only a potency, and that in reality only a finite number of steps would be actualised - in the original paradox, the runner’s paces would actually be 1 metre, or whatever, long. In evolution, if evolution occurs by discrete changes of form, in contradiction of Darwin’s recycled scholastic dictum Natura non facit saltus, then nature too moves in “paces”, and not through an infinite (and therefore non-traversible, if Zeno were correct) continuum.
So moving away from a “change of gene frequencies” model of evolution to some variety of saltational model (including special creation of any kind that isn’t simply gradual gene substitution - for example, the “nudging” of an entire package of complementary genetic changes) - then the number of transitions that ever existed would be strictly finite. To apply that to your example, Australopithecus - let’s assume for argument’s sake a human ancestor - did not gradually morph into, or through, a continuum of forms, but truly transitioned, let’s say into or through H erectus, H Neanderthalis, Denisovans and a few more distinct forms that haven’t been discovered or were never preserved.
In that case, finding a new transitional just adds +1 to the limited menagerie. We are no longer assuming a chronological version of the scholastic “principle of plenitude” in which every variant must have existed in principle, even if there is no evidence for it.
Hybridisation of those few forms, as in our own case, increases the possibilities, but at most by creating one new form from two, or more likely by being absorbed into the existing form.
Evolutionary intermediates, in this scenario - such as a medium size Samotherium which, it is agreed, is not conceivably ancestral to the giraffe, become even less significant than under gradualism, because we are not committed to saying the giraffe neck must have been growing through many divergent and continuous branches. And as I pointed out before, it is as true now as in Darwin’s time that most “transitions” in the fossil record are constructed from intermediates not even believed to be in the direct line of descent.
The question then is whether the evidence favours either model over the other. As far as the fossil record goes, the stasis-saltation pattern has been well publicised since Gould (whose own explanation depends on “accelerated gardualist” assumptions below the resolution of the fossil record. There are good reasons to suppose the fossil record is not nearly as incomplete as gradualism demands.
Even simple sampling methodology confirms that: on an infinite continuum, one would expect to find few fossils of many forms, and seldom (unless in juxtaposition) more than one from any species. In fact, we find many billions of fossils from (currently) only around 250,000 species - a mere fraction of living species… of which incidentally a large poercentage are found as fossils.
That would a truly extraordinary ratio given gradualism, turning Darwin’s “How come we don’t find more species in the fossils?” into the largely ignored “How come we find so many of each species?”
Population genetics applied to transitions tells us only that there appears to be common descent, not whether the large-scale changes occured at a more or less constant rate or not, unless one makes the assumption (contested by many including Gould and Eldredge) that all evolution is essentially scaled-up population genetics.
And so I do say that Zeno’s paradox is irrelevant
(a) because if true it renders gradualism, and all change, logically impossible. That is the very thing Zeno sought to prove by it.
(b) because under the Aristotelian scheme that resolves the paradox, actualised forms are discrete entities anyway, and the number of transitions is strictly finite. It predicts that one will inevitably find variations (if there’s a small, a medium and a large, one can arrange them in ascending order, and that may or may not correpsond to some real sequence of changes), but that one will only actually find a limited number of such variations. The gaps will be real, and will require some explanation beyond “Join the dots.”