Some unpublished Devil Dinosaur art.
You can see Jack took extra care to make sure each panel had plenty of great contrast. A lot of comics pencilers during that era would simply give the inkers a basic outline of the characters, then the inkers would have to spot blacks and even illustrate the backgrounds from scratch, so Jack was great at giving his inkers everything they needed to do their job fast and efficiently. Not only is Jack being unselfish by putting in the extra work — saving his inkers the time and effort it takes to do a good job spotting blacks and drawing the backgrounds — but I think this approach is an example of Kirby being a perfectionist: he really wanted the final image to be something he was satisfied with; he wanted all the elements (foreground, background, shading) to work together in harmony to create a cohesive and dynamic image that met his expectations in terms of craftsmanship and quality.
It’s fun to see how Jack gave different surfaces different textures with his pencil-work. Notice how the linework on the rocks contrasts with the linework of the grass and the linework on the mountain in panel one. I don’t think any of Jack’s inkers always captured that diversity of shading in Jack’s penciled linework — they tended to fill in many (or most) shaded areas with all-black because that was how comics were traditionally done.
I wonder if Jack would have preferred for his inkers to try and more faithfully delineate his pencil strokes in those shaded areas, or did he understandably assume the inkers would fill in those shaded areas in all black (since that was the standard), and the different textures in the penciling phase was a way of filling in the black areas as he was going along that Jack found enjoyable, and/or he found the final result aesthetically pleasing; or maybe that approach simply helped him find the final composition by sketching, and those different textures gave the finished piece a 3-dimensional look he found visually satisfying. A lot of artists simply insert a little “x” in an area that is supposed to be all-black, but as you can see above, filling in those areas with different types of directional lines was part of Jack’s drawing process.
Notice Jack’s shading in the final panel above of the belly of the attacking dinosaur gives the illusion of movement forward. If those shaded area were inked in all-black you would lose that effect. Same with the shadow under the dinosaur, the lines point towards the right enhancing this illusion of left-to-right movement. Observe how the shading lines under Devil’s tail makes it look like it’s swinging horizontally.
Inkers like Mike Royer were incredibly faithful to Jack’s pencils back in the 70s, but I’ve noticed that when Mike does modern recreations of Jack’s work, instead of filling in shaded areas in all-black (as was the traditional method during the 60s and 70s) Mike embellishes the individual pencil lines in the shading, giving the art a look that is even more faithful to Jack’s original pencils.