TangTang,
the undulate(Balistapus undulates) and blueline(Pseudobalistes fuscus) are two seperate triggers. there's actually over thirty different triggers. I have a list of all of the triggers that I have been able to find on the net.
1.Starry triggerfish, Abalistes stellatus
2.Undulate triggerfish, Balistapus undulates
3.Gray triggerfish, Balistes capriscus
4.Bluespotted triggerfish, Balistes forcipitus
5.Finescale triggerfish, Balistes polylepis
6.Queen triggerfish, Balistes vetula
7.Clown triggerfish, Balistoides conspicillum
8.Titan triggerfish, Balistoides viridescens
9.Rough triggerfish, Canthidermis maculates
10.Ocean triggerfish, Canthidermis sufflamen
11.Indian triggerfish, Melichthys indicus
12.Black Durgeon triggerfish, Melichthys niger
13.Pink-tail triggerfish, Melichthys vidua
14.Niger triggerfish, Odonus niger
15.Yellow-faced triggerfish, Pseudobalistes flavimarginatus
16.Blue-and-Gold triggerfish, Pseudobalistes fuscus
17.Blunthead triggerfish, Pseudobalistes naufragium
18.Huma Huma triggerfish, Rhinecanthus aculeatus
19.Assasi triggerfish, Rhinecanthus assasi
20.Lunula Trigger, Rhinecanthus lunula
21.Rectangular triggerfish, Rhinecanthus rectangulus
22.Black-Patch triggerfish, Rhinecanthus verrucosus
23.Whitetail triggerfish, Sufflamen albicaudatum
24.Half-moon triggerfish, Sufflamen albicaudatus
25.Bursa triggerfish, Sufflamen bursa
26.Bridle triggerfish, Sufflamen fraenatum
27.Blue-throated triggerfish, Xanthichthys auromarginatus
28.Blue-lined triggerfish, Xanthichthys caeruleolineatus
29.Striped triggerfish, Xanthicthys lineopunctatus
30.Crosshatch triggerfish, Xanthichthys mento
31.Outrigger triggerfish, Xanthichthys punctatus
32.Sargassum triggerfish, Xanthichthys ringens
I have seen all but 7 of them.