In Yoni's survey of international urinals, he commented on the aquas super genus of urinals. In my comments on that post, I noted how that particular urinal was a member of an increasing rare order of urinalas vulgaris, a.k.a. "pee walls." These urinals are essentially porcelain or tile walls with a single drain down at one edge (see a great example here [link]). Although that particular specimen Yoni documented was sporting trendy "privacy barriers," which is unusual for a urinal of that age, and had a larger tile pattern, studying the drain structure and general layout, it's clear that it's a member of the older vulgaris order.
Experts in the field of urinalogeny have long been searching for the evolutionary pathway between these simpler pee walls and the more complex, individual modern urinal. I believe that I'm the first to document a missing link in this evolutionary chain, discovered in a basement bathroom in a wedding hall in Crown Heights, Brooklyn:
Furthermore, it's possible that the barriers seen in the British specimen actually are early versions of the full-length dividers seen here, and not, as I previously suspected, privacy barriers, which are generally a modern evolutionary trait. Thus, it seems that urinals started growing the dividers from their upper regions, where there is no demand for complicated individual draining systems. Perhaps tile grout (gloopus tilum) was actually incorporated into the urinal species itself (an endosymbiosis)?
These extensions gradually descended downwards, while the lower trough-type drain closed in on itself to form a pipe and individual drain openings. Then, to get our modern urinals, the individual tiles merely needed to separate and shrink upwards, while allowing their underground pipe connections to stretch.
This theory also helps explain urinal reproduction. The tiled structure of pee walls points to binary fission as the likely mechanism. However, this evolutionary pathway suggests that the modern urinal reproduces by using "runners" to sprout up new urinals.
As this is a recent find, I am open to other alternative explanations, so let's hear 'em in the comments!