Kim, the ridgeless RR rescuee whom we've had for five months now, has turned out to be a little more than he seems. He looks like a pure RR, if a little on the stocky, blocky side, and his sister/littermate, whom we visited for the first time today, is almost a dead ringer for him; they're hard to tell apart if you don't know at least one of them well.
From speaking to the neighbour who rescued Kim's sister Gipsy, we found out that the abusive and neglectful previous owner of both dogs had stolen them from a farm some way from here as pups, but not before discovering something of their provenance. Apparently they are mostly RR, but Bullmastiff was introduced into the bloodline at some stage a few generations earlier … or was it Great Dane … he wasn't sure.
So I had a good look at both breeds on YouTube and, based on Kim's somewhat stocky build and broad, blocky head, my money's on Mullmastiff. Great Danes have rather narrow heads and are not a stocky breed by any means. Also, Kim's lower lip juts a little, so it's level with his upper lips, and I saw a similar look on the lower lip on the Bullmastiffs.
The odd thing is that they are as small as they are, if they're RR crossed with Mastiff. Kim's approx. 21 - 22" at the withers (can't get an accurate fix because he won't stay still), and his sister Gipsy is quite small, certainly no bigger than four fifths the size of Kim, and she's more lightly built than Kim in both head and body, looking exactly like a purebred RR, to my untutored eye anyway.
So, anyone wanting to hazard a guess as to which of those big breeds is hovering in the background in the genetic makeup of these two can see both on YouTube at:
http://www.youtube.com/watch?v=dHIrxOr4ES8The female, Gipsy, is the one doing most of the work, btw ;-)
Best, Lachlan