No piece of work is immune from error, and I’ve rarely seen any paper without a mistake in there somewhere if you dig deep enough, even if it’s just a typo. Even so, the point of peer review is to iron out papers and reduce the amount of mistakes and maximise the amount of accuracy. Given the review and editorial process, this makes the scientific literature proper rightly the primary source of research material and information for academics.
However, while the vast majority of what you will (or should!) see cited in a paper is other academic papers this is not the only source. The point of citations is of course to allow other people to track down your information source and not everything is in the scientific, or primary, literature.
At the other end of the scale we have popular literature. Non-reviewed and quite probably non-expert written material. Normal dinosaur books aimed at the public, news articles, bits in magazines, and these days most blogs (including this one) and the like.
However, somewhere in the middle we have what is often called the grey literature. It’s written by an authoritative source and was probably checked, if not actually reviewed, by other professionals. It might contain detailed references and ‘proper’ figures with scale bars, detailed labels, contain specimen numbers and so on. Things like Peter Dodson’s “Horned Dinosaurs” or the “Complete Dinosaur” book and similar fall into this category. So too to various articles in some journals (like opinion pieces, book reviews and the like) and, in all probability, the really solid and referenced blogs like Tetrapod Zoology.
There’s nothing wrong with citing any of these in a paper, in theory at least. And if your only source for a given point or bit of information is the ‘Jumbo A-Z of dinosaurs’ then so be it. However, it’s not what you should be going for if Smith et al. in a paper in Nature is available. No paper is perfect, but much like the concept of argument from authority, it’s generally better to head to the primary literature, though it’s not always possible.