We report the discovery of SDSS J0909+4449, an exceptional system
consisting of a quasar at z = 2.788 strongly lensed by a group of
galaxies at z ˜ 0.9 into three images separated by up to 14 arcsec
based on archival data collected by the Sloan Digital Sky Survey,
extended Baryon Oscillation Spectroscopic Survey, Beijing-Arizona Sky
Survey, the Mayall z-band Legacy Survey, and the Gemini Telescope. We
discuss two hypotheses on the nature of SDSS J0909+4449, i.e. a rare
triply imaged quasar in the naked cusp configuration and a typical
quadruply imaged quasar with the fourth image undetected in this data.
We find that simple lens models can provide excellent fits to the
observed image positions and the non-detection under either hypothesis.
Deeper imaging data, spectroscopic observations, and follow-up
light-curve measurements will be helpful in determining which hypothesis
is correct and provide better constraints on the lens mass distribution.
Nevertheless, given its unusually large image separations, SDSS
J0909+4449 will be a unique probe for the mass structure and the
underlying cooling and stellar feedback processes on group or cluster