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We present resolved HI observations of two galaxies, UGC 9037 and UGC 12506,members of a rare subset of galaxies detected by the ALFALFA extragalactic HIsurvey characterized by high HI mass and high gas fraction for their stellarmasses. Both of these galaxies have M$_*>10^{10}$ M$_\odot$ and M$_\text{HI}>$M$_*$, as well as typical star formation rates for their stellar masses. Howcan such galaxies have avoided consuming their massive gas reservoirs? From gaskinematics, stability, star formation, and dark matter distributions of the twogalaxies, we infer two radically different histories. UGC 9037 has high centralHI surface density ($>10$ M$_\odot$ pc$^{-2}$). Its gas at most radii appearsto be marginally unstable with non-circular flows across the disk. Theseproperties are consistent with UGC 9037 having recently acquired its gas andthat it will soon undergo major star formation. UGC 12506 has low surfacedensities of HI, and its gas is stable over most of the disk. We predict itsgas to be HI-dominated at all except the smallest radii. We claim a very highdark matter halo spin parameter for UGC 12506 ($\lambda=0.15$), suggesting thatits gas is older, and has never undergone a period of star formationsignificant enough to consume the bulk of its gas.

HIghMass - High HI Mass, HI-rich Galaxies at z~0: High-Resolution VLA Imaging of UGC 9037 and UGC 12506