Joe Warren was the 2006 World Champion in Greco-Roman wrestling. Bibiano was a 3-time Mundials Champion in BJJ.
I believe this is the first time that a BJJ Mundials Champ has ever gone up against a wrestling World/Olympic Champion in MMA. (Although the defining, excluding factor here is that there have not been all that many wrestling World/Olympic Champions, not just team members or medalists, to come in and compete regularly in MMA.)
We're far past the style-vs.-style days, and there have certainly already been high-level, even world-class wrestler-vs.-BJJer matchups before (e.g., Kerr-Gurgel, Busta-Lindland, Lindland-Fabio Leopoldo) - but has there ever been an actual World Champion wrestler vs. World Champion BJJ-er before? I can't think of any. The closest I can come up with are the Lindland examples against Busta and Leopoldo, which consisted of an Olympic silver medalist fighting two Mundials Champs.
So is Bibiano-Warren the first? Of course they're both modern-era cross-trained MMA-ers, and it would have been a far more historically significant milestone had this happened several years ago (especially in the 90's and the less multi-dimensional NHB era) - but that would still be an interesting historical footnote to this matchup.
Kevin Jackson vs Sam Adkins
Coleman vs Mutant Morais
i don't think warren will give up a submission
busta vs hendo?
anunaki - busta vs hendo?
Hendo was a national Greco champ and an Olympian, but never a world or Olympic champion.
If your first two MMA fights are booked as Chase Beebe and Kid Yamamoto, and you happen to defeat both, you just might be a complete badass.
Interesting fact WB, love Joe Warren's intense pace and tenacity.
A recent tidbit I got from one of Joe's recent interview. Warren couldn't hear his corner in the Chase Beebe fight but did hear Chase's corner, so he followed his opponent's instructions intended for Beebe. Part of the instructions were to knee so Warren knee'ed and won with a vicious knee and massive cut to Chase's Head.
Kneeblock - Bitteti vs. Frye is actually the first recorded Mundials champ vs. World class wrestler contest I can think of, though I believe it predated the first mundials.
Frye-Bitetti was hugely significant both at-the-time (back when being a BJJ BB in itself was still almost mythically invincible) and historically since it was the first time that a wrestler had beaten down a BJJ BB (let alone a high-level one like Bitetti).
But it would be dubious to categorize Frye as a truly world-class wrestler. As Coleman notably put it when describing the difference in levels of wrestling between himself and Frye - Coleman himself was a world-class wrestler who had made the Olympic team, placed 7th at the Olympics, took 2nd at the World Cup, and had been a D1 NCAA champion - while Frye was an NCAA wrestler who wasn't even a champion at the collegiate level, or even a major player on the senior national level, much less a truly "world" class wrestler.
(By contrast, I included Kerr as being "world class" because he was a NCAA champion and a U.S. Senior National Champion, who actually beat Kurt Angle - more times than Angle beat him, btw - and Angle of course was unquestionably world-class as an Olympic and World Champion.)
anunaki - busta vs hendo?
As HB already pointed out, Hendo never won or even medaled at an Olympics or World Championships. So Hendo-Busta doesn't even trump Lindland-Busta, since Lindland not only made the Olympic team like Hendo did, but medaled.
So I guess so far, behind Bibiano-Warren, it's still Lindland-Leopoldo and Lindland-Busta as the closest it's ever come to a true World Champion vs. World Champion matchup between wrestling and BJJ?