Quote Originally Posted by The Summoner of Leviathan View Post
Arcanist can summon Carbuncle! In theory Summoners should still be able to summon Carby!
Only arcanist can summon carbuncle. The way the job is set up, arcanist learns Summon at level 4 which summons a caster/healer-type pet and Summon II at level 15 (class quest) which summons a tank/support-type pet. What pet is summoned depends on whether you are currently arcanist, summoner, or scholar.

Summon
Arcanist: Emerald Carbuncle (caster)
Summoner: Garuda-egi (caster)
Scholar: Fairy (healer)

Summon II
Arcanist: Topaz Carbuncle (tank)
Summoner: Titan-egi (tank)
Scholar: Fairy (support)

Summon III (SMN level 30 job ability)
Summoner: Ifrit-egi (DD)