err... i do think otherwise: like in the true world, Abyssal Lagiacruses are one kind of Lagiacrus that inhabits the most deep part of the oceans, their skin and glowing horns (they're the only ones of their races to make glow every single spike) should prove it, Normal Lagiacruses or Ivory Lagiacruses wouldn't mutate that fast from subspecies to subspecies, and probably wouldn't go in such a dangerous place like the ocean depths (where only specific creatures that have behaved the habitat would live due to water pressure)... to me Abyssal Lagiacruses are very powerful subspecies of lagiacrus that inhabit the depths and are rarely being seen around like real life abyss fishes.
Well, (unfortunately) it's already confirmed that the three different Lagiacri (the right plural form) are the same >subspecies< (not only species) by Capcom.
While it could be true with normal and Ivory Lagiacrus being the same species, I don't think Lagiacrus can get that adapted to a life in the dark deep sea that it can live there just by getting older or anything.
It's just not a very good thing of Capcom making them just one subspecies. (But the worst thing is still Abyssal Lagiacrus eating Plancton.... WHY!?)
Hellwolf, that doesn't explain, why the normal Lagiacrus turns a little darker, when he's on land for a short time.
It's pretty stupid, that Capcom just said, they're the same species. As Democide said, it COULD make sense for Ivory and normal Lagia, but an animal, that's adapted to live on land could NEVER turn into some super-specialised deap-sea monster (he's got those more fin-like feet, luminescent body parts as many real-life fish in deap-sea and most likely some modification for breathing underwater, wich he does).
I think about Ivory as an more experienced Lagaicrus, that decided to live and hunt on land though and I think, that's more or less the "best" explanation for it.
@The AWC: Why lagi turns a bit different color on land? Well, isn't it kinda obvious? Really simple, he just dries! You know when you make something wet and it changes color a bit, well the water on lagi just dries.