Although the edge-on optical disk of this galaxy looks flat, the extended HI disk is clearly warped into an "integral sign". This galaxy is isolated, so the warp is thought to be a stationary feature that is caused by gas orbiting in a non-spherical dark matter halo potential
As with NGC 4013 this galaxy is isolated (though it does have a faint tidal stream), and yet it's neutral hydrogen shows an integral sign warp (the main disk HI has been removed for clarity). (B&M fig 8.30)
It is thought that the warp in this disk is a transitory response to a merger - a gas rich galaxy has recently merged with the more massive spheroidal galaxy, and the gas is in the process of settling down into a steady flat disk