Deuman lore

What's up with the lack of story for the deuman race? It seems in comparison to the other races, it has barely anything behind it. I heard somewhere that deumans are related to draconic heritage, but couldn't find a source. Does much lore exist for this race? Another thing, why do PSO2 Deumans have horns, but PSP2I ones do not?

While I'm not a lore expert within the working of Phantasy Star, But Duemens in pso2 are "draconic like" because of Haddred's death or this case the result of time travel with his handkerchief that he wore that had his DNA being sent back to the past for the creation of the race, and with PSU's (PSP2I's) it's more has to do with the fact that they are a mutation from the SEED incident.