  We present VLA D-array HI observations of the RSCG42 and FGC1287 galaxy
groups, in the outskirts of the Abell 1367 cluster. These groups are projected
~ 1.8 and 2.7 Mpc west from the cluster centre. The Arecibo Galaxy Environment
survey provided evidence for HI extending over as much as 200kpc in both
groups. Our new, higher resolution observations reveal that the complex HI
features detected by Arecibo are in reality two extraordinary long HI tails
extending for ~160 and 250 kpc, respectively, i.e., among the longest HI
structures ever observed in groups of galaxies. Although in the case of RSCG42
the morphology and dynamics of the HI tail, as well as the optical properties
of the group members, support a low-velocity tidal interaction scenario, less
clear is the origin of the unique features associated with FGC1287. This galaxy
displays an exceptionally long 'dog leg' HI tail and the large distance from
the X-ray emitting region of Abell 1367 makes a ram-pressure stripping scenario
highly unlikely. At the same time a low-velocity tidal interaction seems unable
to explain the extraordinary length of the tail and the lack of any sign of
disturbance in the optical properties of FGC1287. An intriguing possibility
could be that this galaxy might have recently experienced a high-speed
interaction with another member of the Coma-Abell 1367 Great Wall. We searched
for the interloper responsible for this feature and, although we find a
possible candidate, we show that without additional observations it is
impossible to settle this issue. While the mechanism responsible for this
extraordinary HI tail remains to be determined, our discovery highlights how
little we know about environmental effects in galaxy groups.
