I remember frequently checking this book out from my grade school library; it was hardcover, no dust jacket; limited to mammals (worldwide species). It was a ‘tall’ sized book and may have had a pinstripe or harlequin design, on the front cover was an oval/circle template with jungle animals. (I do remember a giraffe). The inner illustrations were not photos, but looked painted/drawn. It looked like an old book, maybe from the ‘40s-‘50s?
A long shot, but I’d suggest looking up the books of Dahlov Ipcar, who paints LOTS of exotic animals and started writing for children in 1947. See here for much more:
https://groups.google.com/forum/#!search/90th$20dahlov$20ipcar$20lenona/rec.arts.books.childrens/GvTAY49E5rA/m9jPZ90uUi4J
Thanks for the suggestion, but I don’t think the illustrations were by Ipcar. The ones in this book seemed more, i don’t know, lifelike. realistic, maybe? They didn’t have an “artsy” style to them like Ipcar’s work usually does. I think the book was middle school (grades 3-5) level.