Apart from that, the differences in the outcome of the reconstructions also reflects the individual variation within the species. For my most recent reconstructions, I once again choose the two Sassenberg skeletons, bull and cow. The Sassenberg bull, a cast of whose skeleton can be seen here has extensive tooth wear and probably was an old specimen. The withers height of the skeleton is 165cm according to Frisch 2010, what means that in life it was probably 175cm tall at the withers. What is interesting is that the Sassenberg bull has unusually low processus spinosi in the shoulder regions, meaning that its hump is not as tall as in other aurochs specimens - compare, for example, with the Kopenhagen bull and other specimens - but still higher than in most domestic bulls. For my reconstruction, I drew higher spines, comparable to other specimens. This is not retouching, but more an attempt to appreciate the average of the species. Here is the result:
There are also a number of skeletons that have a deeper ribcage than this one. Here are some other bull skeletons that I reconstructed on paper a while ago:
From left to right, up to bottom: Sassenberg, Braunschweig, Vig, Kopenhagen. It becomes pretty obvious that an aurochs bull's gross morphology is somehow intermediate between that of a wisent and a Lidia bull. Especially the Kopenhagen bull is rather Lidia-like due to its compact body and the comparably small horns.
The Sassenberg cow is more from the gracile site as well, considering that the Cambridge cow has a way more robust and deep ribcage. Also the horns of this specimens are not that large, compared to others (but still way from small, also considering the keratinous sheath that must have covered them in life). Here is the result:
All in all, it looks like a large-horned mix of a Lidia and Sayaguesa cow with a strongly expressed hump.
Here are both the cow and the bull to same scale (bull 175cm at the shoulders, 145cm at the shoulders):
For the colouration, there are more possibilities than that regarding minor details (forelocks, the extent of the muzzle ring, the colour shades of the cow), but there are a few individuals of modern cattle that match a 100% what I intuitively consider an authentic colour possibility for European aurochs. Both happen to be Heck cattle, but you can easily find these colours in other auorchs-like breeds.
Here for the bull, a Heck bull in Northern Germany:
Maybe it is a kind of bias because this is the first Heck cow I ever saw in my life, but this cow just has the archetypical aurochs cow colour to me. There are other variants however that are also documented in cave art (such as black cows with a red saddle, entirely black cows or entirely brown cows).
I also did head detail portraits for both specimens:
While there are some cows of many breeds that do have a very reminiscent horn shape, I have not seen yet bulls of any domestic breed that have this kind of skull shape with the very elongated snout and frontal area and the small eyes with that prominent eye sockets, although some Lidia and Maltese individuals come more or less close (as far as I can tell comparing living animals in flesh with fossil bones).
I also started doing new aurochs models, and these recent reconstructions will be the basis for them.