Chris,

I am finding a number of entries where there is both "Genus (Subgenus) species" and "Genus species", both as preferred taxon

e.g.
NHMSYS0020470264 Cyanapion gyllenhalii
NHMSYS0020151953 Cyanapion (Bothryorrhynchapion) gyllenhalii

both are preferred and appear on the NBN Gateway, although there is no map associated with the non-subgenus version

There are a number of other examples, particularly in the mollusca e.g. all the following are listed as preferred:
NHMSYS0020528111 Arion (Kobeltia) hortensis
NHMSYS0001701912 Arion hortensis (this has a common name of Arion (Kobeltia) distinctus!)
NBNSYS0100001650 Arion hortensis agg.
NHMSYS0000377646 Arion hortensis seg.

To say the least, this is confusing!

Craig