Alright, an hour in and I feel like I'm making progress. The basic proportions are getting there and I dove in one one of the tw ends, which are the most complicated. In addition to screen grabs I found a rendered 3D model that I can turn around, zoom in on, etc. This is helping fill in the blanks on details the screen grabs don't show.
a couple more hours and I feel pretty satisfied with the overall shape and form. The screen grabs don't show everything so the 3D mode of a real bone is filling in the gaps a bit. But, there are times I'm trying more to match the shapes I'm seeing in the screen-used bone. The way the light kicks in certain spots or has shadows that don't necessarily lineup with the medical 3D file.
Some of the dark/light you're seeing in the sculpt is discoloration in the clay. It's not that bumpy. Right now everything is pretty smooth. A little more aligning of some details and I'll do a pass to add the "rough" spots and texture.
My finished bone sculpt went into some silicon this week. After cutting the mold open to free my clay model, I was surprised how little damage there was. Didn't really matter, as I planned on scrapping the clay sculpt. I poured a rotocast cast in the mold and the first cast turned out great. I might do another one to see if I can hide some of the seam lines a bit more.
Also, I made progress on my monolith display stand. I built the monolith in Fusion 360 and printed it out with a hollow back (like an open face box. Then glued a 3/4" chuck of MDF in the back so the whole thing has some weight. I'll be drilling a couple pegs for the front that the bone will hang from.
Now I'm on to painting. I want to try to match the coloration, weathering and scratches of my screen grabs.