Balerion the Black Dread | Dragon

Balerion of "A Song if Ice and Fire", with Aegon by his side. Book inspired illustration done in 2014, the smoke and fire supposed to rise from the walls of Harrenhal, visible in the oldest panoramic variant of the image. It is also a test on Balerion's look and size: he should be able to swallow a mammoth, thus Aegon is just a tiny figure; and since GoT dragons supposed to have black bones I gave him black teeth. But maybe dragon skeletons just looked as such to ASoIaF characters in the books (I don't remember who was it that said the bones were black), but weren't really black when dragons were still alive? Also the skeletons are light colored in the tv show. Any ideas?