What is a wraxapod?

No idea, it's a made-up word.

If you read through the page, it gives a description about what Wraxapods are. While they are a made-up animal, it is highly likely that E.E. Knight took inspiration from a prehistoric beast known as an Indricothere, which is the world's largest known land mammal that ever existed. Indricotheres could grow to be three times the size of an elephant, had long giraffe-like necks that could browse the tops of trees, and were covered in thick hides and were essentially invincible to any predators once they reached adulthood, and are also believed to be close relatives to rhinos.

Hope that helps. ^^