In Islam, are there limits on sex between a married couple?
Anal sex is strictly strictly forbidden
Though there is no direct verse related to it but there but this is general consensus among Sunnis Muslim that Anal sex between husband and wife is not allowable. It is also stated in tafsir of the above verse that sex must occur only where it is supposed to be, not in any additional place.
Here are some hadiths that shows it is prohibited.