According to the Henderson's Chicken Chart they are two different breeds but when I did a search on BYC for the Welsumer's I got a Marans page, so now I'm confused.
Welsummers and Marans are definitely separate breeds. If you see a problem with a BYC page (like it has conflicting or wrong information), you might want to send the link via PM to Nifty or one of the mods, especially if it's an "official" page, so that the misinformation can be repaired.
Whoa, yeah, try to get the problem fixed!
The Marans folks would flip over before they're in the grave if they thought someone thought a Welsummer was a Marans. I actually dont know that much about Welsummers, but I do believe the Marans originated in France, there is always an "s" at the end, there is a very passionate following (yeah, I'm getting there) for this historic breed. Welsummers are cool too, but an entirely different breed that puts out a deep terra cotta colored eggs. (Marans lay a darker brown egg).......Good luck, its actually a fun subject to explore!
OK, seems my confusion came from my putting Welsumer in the search engine under hatching eggs and only came up with a thread on Marans, must be someone in that thread mentions Welsumer's but the thread is 14 pages long so I didn't actually see that, just my assumption.
When you're doing the search, make sure you type "Welsummer" with two "m"s. I do see the word with one "m" occasionally, but you'll find much more info if you spell it with two.