The anatomy of Glaurung

[Galin]

Tolkien painted a picture of Glaurung (Glorund) too -- if you have JRRT Artist and Illustrator for example, see page 51. It's early but I thought some might be interested in any case. And while not about Glaurung specifically, in 1938 Tolkien gave a lecture on Dragons (to children), using slides of his own drawings of Glorund, the 'coiled dragon' and others. In this he noted

'(...) Of course, size is also a consideration... A respectable dragon should be twenty feet or more.

The true dragon at his least was sufficiently large to be a terrible foe... It was the function of dragons to tax the skill of heroes,...'

I general he described...

'... a serpent creature but with four legs and claws; his neck varied in length but had a hideous head with long jaws and teeth or snake-tongue. He was usually heavily armoured especially on his head and back and flanks. Nonetheless he was pretty bendable (up and down or sideways), could even tie himself in knots on occasion, and had a long poweful tail...' (...) JRRT

There's more of this lecture published in Hammond And Scull's Reader's Guide