It's not from flatland, I had this kind of stuff a long time before i started to flatland.

It's because not wearing gloves. Especially in winter, you just have too dry skin. Try putting some balsam or hand cream(with glicerine) on it everyday after flatlanding and before sleep.

i get it too. my hands are ruined, they are one solid, dry calous. and no matter how many times i wash them they are still like black on the palms

Ive tried gloves. ive tried every grip out there

i never had this problem in 15 years of racing mountainbikes downhill...

gloves actually make it worse if anything..

I'm not a dermatologist, but I did stay in a Holiday Inn Express once...

That looks to me like a combination of things... dry skin, abrasion, and possibly a fungus of the same strain as athlete's foot. I used to get the fungus on my fingers when I worked in a Subway for a few years and had to A: wash my hands every few minutes, and B: put on those goddamn sanitary plastic gloves.

Try to get that crack to heal up as much as you can... I'd use Neosporin or something similar and keep it bandaged as best as you can. Try to baby it. If the crack seals up after a few days, get some Lamisil or Tinactin and try and treat it like regular old athlete's foot. If it starts to clear up after that, find yourself some good skin lotion (I like St. Ives) and keep your hands moisturized as best as you can manage.

But you shouldn't completely trust me on this; it's been several years since I stayed in that hotel. If you're worried (and insured) go see a doctor. Or a dermatologist.

If you're not all that worried, maybe you'll get lucky and it'll just go away.

ive got a blister before in that same spot from worn grips. i could be that it too dry outside so it just cracked.

maybe a long shot, but perhaps wash your hands frequently when riding. its posible a form of athelete's foot/ fungus that grows on sweaty hands. that particular area may be very susceptable. do your grips have flanges? that may also contribute.

couldnt hurt.

yep i get exact same problems  hands are so hard i can put naked flame on em and not feel a thing , my guess is its just the british climate though as i found after 2 months in spain it all healed up and hands were relatively normal again and that was with riding more than usual so i just put it down to climate and riding .