More recently two articles have been published, still a small number considering the research done on other organisms, that detail cranial anatomy as well as morphology. These are good papers and, the paper on juvenile cranial anatomy I can say for certain, because it is a JVP article so I could access it and read it, is quite informative and not a bad read at all. The other paper, focusing on morphology and cranial anatomy is available through Wiley's publication of the Zoological Journal of the Linnaen Society. The article was published in 2011 and was inspired by notes and illustrations of Alan Charig that were passed on to the lead author David Norman after Charig's passing in 1997. That makes it a touching story behind an interesting anatomical discussion I think.