  We present a new radial velocity measurement that, together with a
trigonometric parallax, proper motion and signs of low gravity from the
literature, confirms that SDSS J111010.01+011613.1 is a new T5.5 bona fide
member of AB Doradus. Fitting $\lambda/\Delta\lambda$ $\approx$ 6000 FIRE
spectroscopy in the 1.20-1.33 $\mu$m region to BT-Settl atmosphere models
yielded a radial velocity of $7.5 \pm 3.8$ km s$^{-1}$. At such a young age
(110-130 Myr), current evolution models predict a mass of $\sim$ 10-12
$M_{\mathrm{Jup}}$, thus placing SDSS J1110+0116 well into the planetary-mass
regime. We compare the fundamental properties of SDSS J1110+0116 with a
sequence of seven recently identified M8-T5 brown dwarf bona fide or
high-confidence candidate members of AB Doradus. We also note that its
near-infrared $J-K$ color is redder than field T5-T6 brown dwarfs, however its
absolute $J$-band magnitude is similar to them. SDSS J1110+0116 is one of the
few age-calibrated T dwarfs known to date, as well as one of the coolest bona
fide members of a young moving group.
