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Seven-arm Octopus
Large female Haliphron atlanticus (0.69 m ML) caught in 2002.
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Order: Octopoda Superfamily: Argonautoida Family: Alloposidae Verrill, 1881 Genus: Haliphron Steenstrup, 1861 Species: H. atlanticus
Binomial name
Haliphron atlanticus Steenstrup, 1861
Synonyms
Alloposus mollis Verrill, 1880 ?Octopus alberti Joubin, 1895 Alloposus pacificus Ijima & Ikeda, 1902 Heptapus danai Joubin, 1929 Alloposus hardyi Robson, 1930 ?Alloposina albatrossi Robson, 1932

The Seven-arm Octopus (Haliphron atlanticus) is the largest known species of octopus based on scientific records, with a total estimated length of 4 m and weight of 75 kg.^[1][2] However, there have been disputed claims of even larger octopuses of the species Enteroctopus dofleini.

Contents 1 Description 2 See also 3 References 4 Further reading 5 External links

The Seven-arm Octopus is so named because in males the hectocotylus (a specially modified arm used in egg fertilization) is coiled in a sac beneath the right eye. Due to this species' thick gelatinous tissue, it is easily overlooked, giving the appearance of just seven arms.

In 2002, a single specimen of giant proportions was caught by fisheries trawling off the eastern Chatham Rise, New Zealand. This specimen, the largest of this species and of all octopuses, was the first validated record of Haliphron from the South Pacific. It had a mantle length of 0.69 m, total length of 2.90 m, and weight of 61.0 kg, although it was incomplete.

The type specimen of H. atlanticus was collected in the Atlantic Ocean at 38°N 34°W. It is deposited at the Kobenhavns Universitet, Zoologisk Museum in Copenhagen.^[3]

The genera Alloposina Grimpe, 1922, Alloposus Verrill, 1880 and Heptapus Joubin, 1929 are junior synonyms of Haliphron.

Haliphron atlanticus (70 mm ML)

Oral view of the same specimen

• North Pacific Giant Octopus (Enteroctopus dofleini)
• Cephalopod size

1. ^ O'Shea, S. 2004. The giant octopus Haliphron atlanticus (Mollusca : Octopoda) in New Zealand waters. New Zealand Journal of Zoology 31(1): 7-13.
2. ^ O'Shea, S. 2002. Haliphron atlanticus — a giant gelatinous octopus. Biodiversity Update 5: 1.
3. ^ Current Classification of Recent Cephalopoda

• Bakken, T. & T. Holthe 2002. Haliphron atlanticum (Cephalopoda, Alloposidae) caught in Skorafjorden (64°N), Norway. Fauna norv. 22: 37-38.
• Willassen, E. 1986. Haliphron atlanticus Steenstrup (Cephalopoda: Octopoda) from the coast of Norway. Sarsia 71: 35-40.

• CephBase: Seven-arm Octopus
• Tree of Life web project: Haliphron atlanticus
• The giant octopus Haliphron atlanticus (Mollusca: Octopoda) in New Zealand waters
• BBC News: Giant octopus puzzles scientists