Trivia time
What would students of Standardbred breeding find odd about Sir Dalrae's p, 1:56 $678,314 breeding.
looking,
I thought to give some others a chance to answer your question, however the stampede has been overwhelming

The transitional accomplishments of Sir Dalrae for a young horse were quite remarkable, although certainly not rare (at least then or in earlier times).
A golden cross of Volomite-Margaret Spangler (by Guy Axworthy) has left behind pacing bloodlines far too numerous to count.
http://www.mi-harness.net/publct/hh/fourkind.html http://www.***/publct/mrgtspnglr.html
In addition there was at one time a race created by the Hambletonian Society named The "Hambletonian Pace" with its premise being the possibility to recover stakes payments for owners of trotters that had made the transition to the pacing gate (believe that same race today is the Tompkins-Geers Stakes).
I'm sure there are many other family's of trotting-bred horses that have made the gait transition (and vice versa), which I've failed to mention.
In addition there have been some very notable double-gaited horses with perhaps the most notable having been Calumet Evelyn. Hodgen was another double-gaited horse that most people today do not recall for that quality.