Table 3 Comparison of Grimpoteuthis imperator sp. nov. with all other presently known species of Grimpoteuthis, listed in alphabetical order

G. abyssicola O’Shea, 1999

Tasman Sea, South Pacific Ocean, 35° 35.1′ S, 160° 57.1′ E (https://tinyurl.com/uzuj4w9), 3145–3180 m depth

...having fewer suckers (68–74 vs. 77), shorter cirri (1.0× vs. 2.5× MSD), presence of a radula, and shell characters (weak shoulder blades vs. no shoulder blades, parallel shell wings vs. expanded shell wings)

G. bathynectes Voss & Pearcy, 1990

Tufts Abyssal Plain, North Pacific Ocean, 45° 01.1′ N, 135° 12.0′ W (https://tinyurl.com/w7b4nv2), 3932 m depth

...having more suckers (68–74 vs. 47–58), shorter cirri (1.0× vs. 1.1× MSD), presence of a radula, different position of web nodules (33–34 vs. 26), and shell characters (weak shoulder blades vs. no shoulder blades)

G. boylei Collins, 2003

Porcupine Abyssal Plain, North Atlantic Ocean, 48° 47′ N, 16° 30′ W (https://tinyurl.com/ubcxk5w), 4845–4847 m depth

...having more suckers (68–74 vs. 55–58), shorter cirri (1.0× vs. 1.9× MSD), different position of web nodules (33–34 vs. 31), and absence of enlarged suckers near web nodules

G. challengeri Collins, 2003

Porcupine Abyssal Plain, North Atlantic Ocean, 48° 56′ N, 15° 45′ W (https://tinyurl.com/u77dj8q), 4828–4838 m depth

...having shorter cirri (1.0× vs. 2.5× MSD), absence of enlarged suckers near web nodules, and shell characters (weak shoulder blades vs. well-developed shoulder blades)

G. discoveryi Collins, 2003

Porcupine Seabight, North Atlantic Ocean, 49° 35′ N, 14° 01′ W (https://tinyurl.com/tuz78ms), 4190–4255 m depth

...having more suckers (68–74 vs. 56–61), shorter cirri (1.0× vs. 1.2× MSD), presence of a radula, different position of web nodules (33–34 vs. 31), and absence of enlarged suckers near web nodules

G. hippocrepium Hoyle, 1904

Panama Basin, East Pacific Ocean, 02° 35′ N, 83° 53′ W (https://tinyurl.com/vl5rmjh), 3332 m depth

...having more suckers (68–74 vs. 50), different position of web nodules (33–34 vs. 25), and shell characters (weak shoulder blades vs. no shoulder blades, convex shell saddle vs. flat shell saddle)

G. innominata O’Shea, 1999

Chatham Rise, South Pacific Ocean, 42° 36.79′ S, 176° 09.81′ W (https://tinyurl.com/ux4stlu), 2000 m

...having more suckers (68–74 vs. 50–60), presence of a radula, different position of web nodules (33–34 vs. 22–24), gill shape (half-orange vs. semi-sepioid), and shell characters (weak shoulder blades vs. well-developed shoulder blades, parallel shell wings vs. expanded shell wings, convex shell saddle vs. convex shell saddle with median ridge)

G. meangensis Hoyle, 1885

Southwest off Pulau Kakalotan, South Pacific Ocean, 04° 33′ N, 127° 06′ E (https://tinyurl.com/rzfjdsm), 925 m depth

...having more suckers (68–74 vs. 60–70) and shell characters (weak shoulder blades vs. well-developed shoulder blades, convex shell saddle vs. flat shell saddle)

G. megaptera Verrill, 1885

Atlantic Abyssal Plain, North Atlantic Ocean, 36° 05.5′ N, 69° 51.8′ W (https://tinyurl.com/u8mnezr), 4600 m depth

...having shorter cirri (1.0× vs. 2.0× MSD)

G. pacifica (Hoyle, 1885)

Coral Sea, South Pacific Ocean, 13° 50′ S, 151° 49′ E (https://tinyurl.com/u9c8gx3), 4500 m depth

...having more suckers (68–74 vs. 52), shorter cirri (1.0× vs. 2.0× MSD), location of proximal cirri (between suckers 4–5 vs. 6–8), and absence of enlarged suckers near web nodules

G. plena Verrill, 1885

Atlantic Abyssal Plain, North Atlantic Ocean, 37° 35′ N, 71° 18.8′ W (https://tinyurl.com/vu3ynqs), 2000 m depth

...having more suckers (68–74 vs. 55), shorter cirri (1.0× vs. 1.2–1.6× MSD), and absence of enlarged suckers near web nodules

G. tuftsi Voss & Pearcy, 1990

Tufts Abyssal Plain, North Pacific Ocean, 45° 05.2′ N, 134° 43.4′ W (https://tinyurl.com/rf58bpj), 3900 m depth

...having shorter cirri (1.0× vs. 1.5–3.5× MSD), absence of enlarged suckers near web nodules, absence of a thin web between suckers, significantly shorter arms, and shell characters (weak shoulder blades vs. well-developed shoulder blades, convex shell saddle vs. convex shell saddle with transverse groove)

G. umbellata Fischer, 1883

Iberian Abyssal Plain, North Atlantic Ocean, 37° 55′ N, 20° 22′ W (https://tinyurl.com/rtxcfj8), 2235 m depth

...having more suckers (68–74 vs. 65–68) and shorter cirri (1.0× vs. 1.2× MSD)—note that the single (and LECTOTYPE) specimen is badly damaged and likely a G. discoveryi or G. wuelkeri [31]

G. wuelkeri Grimpe, 1920

Gulf of Cadiz, North Atlantic Ocean, 35° 46′ N, 08° 16′ W (https://tinyurl.com/ufb2cx8), 2055 m depth

...having shorter cirri (1.0× vs. 2.5× MSD), different position of the web nodules (33–34 vs. 28), gill lamellae count (8 vs. 6–7), and shell characters (weak shoulder blades vs. well-developed shoulder blades, convex shell saddle vs. convex shell saddle with median ridge)