It's actually a complex plant!
Given some of the characteristics of the Yara, such as a 'large mouth with no teeth', it's attachment to trees, and a relatively nonsensical body structure, this makes more sense that's it's not actually an animal, it's a predatory plant. The large mouth with no teeth made me think of the Rafflesia flower.
Rafflesia flowers are absolutely gigantic flowers, three feet across, and are known parasites. They loves tapping into vines because vines are a great source of water. And, contrary to popular assumption, the Rafflesia itself is not a carnivorous plant. True, it smells of rotting meat because it loves attracting insects, but it doesn't actually eat the insects itself - they're used (possibly) in the pollination process. (The pollination process of Rafflesia flowers isn't well understood at this point.)
So the Rafflesia-like flowers form the head of the Yara, modified a bit to give it yellow spots, and thus the appearance of yellow eyes. The suctions cups of of the fingers? Well, they're actually part of the vine that the Rafflesia flower is part of. That's right - the Yara is actually composed of two plants working together.
Something like the Devil's Snare would be perfect for this, unfortunately, we have no confirmation of it's existence, so we're going to do this based off a plant we do know exists - bladderworts. These lovely little suckers use vacuums to suck in bugs, but there's no reason why such a mechanism couldn't be adapted with some sharp needle-like growths to suck blood into the plant. And it's native to Australia. (Of course it's native to Australia, why wouldn't it be?)
Except now we run into another problem - bladderworts aren't vines. So, naturally, we'll need to introduce a host vine into this equation. (Technically four, including the tree.) So we have a Rafflesia-like flower which serves as the head, which inserts into a hapless vine. The vine then grows over the tree, but it needs extra water where it can get it due to the Rafflesia's flower need for water, so the vine adapts to serve a symbiotic relationship with bladderworts. Whenever someone goes by the tree and rests against the bladderworts, they impale him and suck up the blood for extra nutrients and water.