Members of the Sepiolida are short (mostly 2-8 cm ML), broad cephalopods with a rounded posterior mantle.

Brief diagnosis

A sepioid ...

• with a short, rounded body.
• without a cuttlebone.

1. Head
1. Eye pore outside of ventral eyelid.
   

   Figure. Lateral view of head of Rossia sp., 19 mm ML, female, preserved. Arrow points to eye pore.

2. Mantle
1. Dorsal margin fused to or free from head.
2. Ventral mantle adductor present.


Figure. Ventral view of mantle cavity of Rossia sp., preserved. Arrow points to the cut surface of the ventral mantle adductor where it had attached to the ventral mantle wall. Anteriorly the adductor muscles pass to either side of the intestine. Photograph by R. Young.

3. Fins
1. Fins broad (length ca. less than two times, usually equal to, individual fin width).
2. Attachment of posterior fin-lobes broadly separated.
   
   
4. Shell
1. Shell a thin or rudimentary gladius or absent.