All of the illustrations and photographs on this website are the copyright of Scott Hartman, unless otherwise noted. If you are interested in licensing any of them, please contact me.
Because skeletal reconstructions combine scientific data with various levels of educated inference they fall into a something of a copyright gray area. To avoid misunderstandings I'll elaborate on how I* view them:
The skeletal diagrams I produce are intended as scientific representations of real animals. As a result items like general proportions, pose, and specific anatomical details (e.g. the position and shape of the eye socket) are not copyrightable. Moreover, I want them to be used as references.
That said, the images themselves are copyrighted - you can't decide to put one in a book, museum display, etc. without licensing them. And while the pose itself can be copied (in fact, please do) the outline of the image cannot be - i.e. if you make your own skeletals please adopt the pose, but you can't cut and paste the outline onto a children's toy without permission.
Could you clarify for specific scenarios?
Sure, but first let's make use of an analogy: I run a blog on this website as well. The ideas and data I share on the blog cannot be copyrighted, but the specific words in the order I've arranged them belong to me. People are free to take those concepts and write about them on their own blogs (in fact I want them to), use them as the basis for a documentary, etc, although doing so without attribution is impolite. If you like you can print out my blogs and read them in the privacy of your own home, or even share them with a colleague. On the other hand you cannot take the blog posts and make them into a book and sell them. In my view skeletal reconstructions work in much the same way.
Putting that into specifics - if you are making use of the images as a reference for creating non-commercial artwork, you don't need permission. If you later decide to post that work online (in a non-commercial sense) that's fine too, but please cite me (better yet, link to my site).
If you are doing commercial work and want to reproduce or modify the images in any way you need permission. If you are doing commercial work and want to use them as general anatomical references I don't feel that breaks copyright law, but that doesn't excuse being impolite. Recognition and links are the currency of the internet (and common courtesy is the currency of human decency), so please use them.
As a general policy I would prefer to be contacted ahead of any commercial use - I enjoy learning how my work is being used, and as an added benefit I can make sure the commercial work isn't too derivative before there is any trouble. Better yet, hire me. My rates are reasonable, I have 17 years of experience doing commissions and consulting for all manner of media projects, and I bend over backwards to make sure the needs of clients are met. I realize that not every project has the same budget (or even a proper budget at all), but if you contact me we can at least make sure proper credit is given, and that there will be no hard feelings after the fact.
As many internet denizens know, there is a thing called "fair use." If you know what it is and it applies to you, go right ahead and fairly use my content, but please make sure you credit me when using them. At times the internet skates dangerously close to (and sometimes right over) the line that delineates fair use. I'm usually pretty reasonable, especially with academic or educational applications, so if you are in doubt at all please drop me a line first.
*I am not a lawyer, so you should not construe my statements as in any way indicative of the legal views of other content owners.