You can check out the whole O'Reilly menagerie at https://www.oreilly.com/animals.csp.
(disclaimer: I worked on the book)
A list of the animals, and some history:
http://www.oreilly.com/animals.csp https://www.oreilly.com/ideas/a-short-history-of-the-oreilly...
https://www.oreilly.com/content/a-short-history-of-the-oreil...
TL;DR:
> Some of the people at O’Reilly were taken aback: they thought the animals were weird, ugly, and a bit scary. But Tim [O'Reilly] got it immediately—he liked the quirkiness of the animals, thought it would help to make the books stand out from other publishers’ offerings—and it just felt right.
They even have a browser which helps you identify the animal:
https://www.oreilly.com/animals.csp