Cuttlings

Cuttlings are a species of humanoid cephalopods from the Cephalopod dimension. They look the same as octolings and inklings but have 'BONES. 'This means that cuttlings do not have the ability to leave their humanoid form. (cuttlings are not canon outside of this universe)

members

-Captain Cuttlefish

-Callie

-Marie

origins

Cuttlings evolved alongside inklings and octarians but at some point they decided fuck you we are growing bones. This made them unable to morph into their cuttlefish form and put them at a disadvantage against the octarians and inklings. Long story short the cuttlings nearly went extinct and only a few remain today. They are shunned by the rest of society for being different (cephalopods are very specist).

theory behind cuttlings

Captain cuttlefish is the only character in a splatoon game to have the name Cuttlefish. He is stated to be an inkling on inkipedia but this could easily be him attempting to hide his identity. Hence why his grandchildren Callie and Marie adopt the title of "Squid sisters" to avoid being exposed as cuttlings. In splatoon, captain cuttlefish is seen to have ribs, no other characters have or reference bones in any way besides Callie and Marie, who are related to him.