The largest predators in Earth\u2019s oceans are typically vertebrates, so when palaeontologists recently announced they\u2019d found fossils from a 19m-long octopus that lived during the Late Cretaceous, it\u2019s no surprise a lot of people were left scratching their heads.<\/p>\n
This colossal cephalopod is perhaps the closest palaeontologists have ever got to finding a real-life kraken.<\/p>\n
At approximately 19m in length, it\u2019s not only the largest\u00a0octopus\u00a0that ever lived, but perhaps the largest underwater predator from the Late Cretaceous; larger even than\u00a0Mosasaurus hoffmani<\/em>, a 17m-long marine reptile that was long considered the\u00a0apex predator\u00a0of the period.<\/p>\n Such large estimates also make\u00a0N.haggarti<\/em>\u00a0the largest non-colonial invertebrate ever discovered. The largest known prior to\u00a0N.haggarti\u2019<\/em>s discovery were the\u00a03m-long millipede ancestor\u00a0Arthropleura<\/em>\u00a0and the\u00a02.5m-long predatory sea scorpion\u00a0Jaeklopterus<\/em>.<\/em><\/p>\n Today, the title of \u2018largest non-colonial invertebrate\u2019 is held by the enigmatic\u00a0colossal squid\u00a0(Mesonychoteuthis hamiltoni<\/em>), a distant relative of\u00a0N.haggarti<\/em>\u00a0that can reportedly grow up to 14m in length – though the largest ever, officially recorded complete specimen only measured 4.2m.<\/p>\n N.haggarti\u00a0<\/em>belongs to a genus of extinct octopuses that was first described in 2008 following the discovery of a smaller (but still relatively large) species known as\u00a0Nanaimoteuthis jeletzkyi<\/em>. This close relative was originally estimated to have reached sizes of 1.1m, but according to a recent study that re-estimated the size of\u00a0N.haggarti<\/em>, it may have grown to lengths of 7.7m.<\/p>\n Both\u00a0N.haggarti<\/em>\u00a0and\u00a0N.heletzkyi\u00a0<\/em>are what\u2019s known as cirrate octopuses. This group is distinguished from other octopuses by having small, internal shells and two fins on their heads,\u00a0which they use to swim. They\u2019re also exclusively deep-sea creatures, living at depths in excess of 300m and sometimes as deep as several thousand metres!<\/p>\n Nanaimoteuthis<\/em>\u00a0is the oldest known member of this group and therefore a long-lost ancestor of several living, ridiculously cute species such as the\u00a0dumbo octopus, the flapjack octopus, and the big-finned jellyhead octopus – seriously, check out photos of these deepsea critters, they\u2019re\u00a0amongst the cutest animals on Earth.<\/p>\n While\u00a0N.haggarti\u00a0<\/em>has made the headlines in recent weeks, the species was actually discovered in 2008 and at the same time as\u00a0N.jeletzkyi<\/em>.<\/p>\n It was originally named\u00a0Paleocirroteuthis haggarti<\/em>\u00a0based on the discovery of two partial lower jaws from rocks belonging to the 84-million-year-old Haslam Formation on Vancouver Island, Canada. At the time they were discovered, both\u00a0N.jeletzkyi\u00a0<\/em>and\u00a0P.haggarti\u00a0<\/em>were considered\u00a0vampire squid\u00a0based on the size and shape of their jaws.<\/p>\n After\u00a0recently re-examining more than a dozen fossil jaws\u00a0previously found on Vancouver Island, as well as in Hokkaido, Japan, researchers identified a giant, exceptionally well-preserved specimen. This specimen allowed them to revise\u00a0Paleocirroteuthis haggarti<\/em>, re-assign it to\u00a0Nanaimoteuthis<\/em>, and identify the genus as a type of octopus, rather than a\u00a0vampire squid.<\/p>\n As well as revising the taxonomy of this giant octopus, researchers were able to use this newly identified, well-preserved specimen to re-estimate its size. They did this by studying the relationships between jaw size, head size, and body size in living octopuses, which led them to their new, jaw-dropping estimates of 7-19m.<\/p>\n Even the lowest estimates place\u00a0N.haggarti<\/em>\u00a0in a similar size bracket to the colossal squid and make it nearly twice the size of the\u00a0Giant Pacific Octopus\u00a0(Enteroctopus dofleini<\/em>) – the largest species of octopus alive today, measuring 5m across when stretching its arms.<\/p>\n Based on where specimens of\u00a0N.haggarti\u00a0<\/em>and\u00a0N.jeletzkyi<\/em>\u00a0have been found – Vancouver Island, Canada, and Hokkaido, Japan – researchers believe these giant octopuses inhabited the North Pacific Ocean.<\/p>\n The smaller of the two species of\u00a0Nanaimoteuthis<\/em>,\u00a0N.jeletzkyi,<\/em>\u00a0lived from 100 to 72 million years ago, while the larger,\u00a0N.haggarti<\/em>, lived for a much shorter period roughly 84 million years ago.<\/p>\n As cirrate octopuses, it\u2019s believed both\u00a0N.haggarti\u00a0<\/em>and\u00a0N.jeletzkyi\u00a0<\/em>inhabited deep waters, though perhaps not quite as deep as many of their living relatives. The cutest of\u00a0Nanaimoteuthis\u2019<\/em>\u00a0relatives, the dumbo octopus, has been sighted at depths exceeding 7,000m!<\/p>\n It\u2019s unknown exactly how deep these giant octopuses would have ventured; researchers think they stuck primarily to the shelf seas of the circum-North Pacific, which was the largest ocean during the Late Cretaceous. The mean depth of the Pacific Ocean today is 4,000m.<\/p>\n Most living octopuses are carnivorous, consuming a variety of soft and hard prey. Their diets consist mainly of crustaceans, shelled molluscs, and bony fishes, though they are also known to eat cephalopods, including squid, cuttlefish, and even other octopuses!<\/p>\n The act of feeding on hard prey creates identifiable patterns of wear on the mouthparts of octopuses. From studying these patterns on extant octopuses and comparing them to patterns seen on specimens of\u00a0N.haggarti\u00a0<\/em>and\u00a0N.jeletzkyi<\/em>, researchers have been able to work out that these giant, extinct octopuses ate more hard-shelled animals than their living relatives.<\/p>\n Hard, coil-shelled cephalopods known as ammonites were some of the most abundant animals in Late Cretaceous oceans. These iconic invertebrates were preyed on by mosasaurs,\u00a0pliosaurs, plesiosaurs, ichthyosaurs, and – if the latest research is anything to go off – giant octopuses as well.<\/p>\n During their research, the authors of the latest study on\u00a0N.haggarti<\/em>\u00a0also spotted long scratches distributed on wide areas of the jaw, which they believe reflects \u201cthe dynamic use of the entire jaw for dismantling prey.\u201d This kind of behaviour in cephalopods has been linked to highly developed brains and increased levels of cognition, suggesting this boneless behemoth was not only giant, but devilishly smart too.<\/p>\n It\u2019s likely only the largest predators of the period could have taken on a fully-grown\u00a0N.haggarti\u00a0<\/em>– and even then they might have gotten more than they bargained for, soon finding themselves as dinner for the \u2018Kraken of the Cretaceous\u2019.<\/p>\n N.jeletzkyi<\/em>, on the other hand, may have been targeted by\u00a0lots of different predators, due to its smaller size. Based on the preserved stomach contents of mosasaurs and other marine reptiles, we know they had a particular taste for cephalopods; though it\u2019s uncertain whether they dined on\u00a0N.jeletzkyi\u00a0<\/em>specifically.<\/p>\n While\u00a0N.haggarti\u00a0<\/em>may have been depicted warring with, and even consuming, mosasaurs, it seems unlikely the two predators would have ever met.\u00a0N.haggarti\u00a0<\/em>was most likely a deep-dwelling octopus, while mosasaurs were primarily shallow-water marine reptiles that needed to stay near the surface where they could breathe atmospheric air.<\/p>\n That said,\u00a0sperm whales\u00a0(air-breathing marine mammals) are capable of holding their breath for more than two hours as they dive to depths of more than 3,000m to hunt giant and colossal squid – it\u2019s not beyond the realms of imagination to think some mosasaurs might have been able to do the same.<\/p>\n Not everyone has accepted the jaw-dropping estimated lengths proposed by this latest study on\u00a0N.haggarti<\/em>, published April 23rd, 2026, in the journal\u00a0Science<\/em>.<\/p>\n Craig R. McClain, an animal body size expert at Duke University in Durham, USA, suggested in a recent post on\u00a0Bluesky<\/em>that lengths of 7-19m may be overestimated.<\/p>\n \u201cI know everyone wants there to be a Giant Cretaceous Octopus but after looking at methods and tables, I really don\u2019t think this is a reality,\u201d wrote McClain shortly after the release of the latest study.<\/p>\n Other researchers have pointed out that determining body size in cephalopods from their jaws alone is very species dependent, suggesting that deriving size estimates of extinct species from extant species is fraught with problems.<\/p>\n The evolutionary history of octopuses has puzzled palaeontologists for centuries. Just recently, a 300-million-year-old fossil thought to be the world\u2019s oldest octopus was\u00a0re-identified as a long-lost relative of modern nautiluses.<\/p>\n Using the latest synchrotron imaging techniques, the University of Reading\u2019s Thomas Clements examined the controversial fossil and found evidence of a ribbon-like feeding structure (known as a radula) that had 11 tooth-like elements per row. Since octopuses only have seven or nine, this ruled them out of his prehistoric lineup.<\/p>\n Instead, the tooth-like elements matched those of a fossil nautiloid known as\u00a0Paleocadmus pohli<\/em>, which was already known from the same site where the supposed \u2018oldest octopus fossil\u2019 was found.<\/p>\n Like octopuses, nautiluses are cephalopods – themselves a group of derived molluscs. These exclusively marine animals are characterised by a prominent head and a set of arms (or tentacles) modified from the primitive foot of their molluscan ancestors. Based on fossil evidence, they emerged in the Cambrian roughly 530 million years ago.<\/p>\n However, it wasn\u2019t until nearly 400 million years later, in the Middle Jurassic (approximately 155 million years ago), that octopuses finally appeared. This makes\u00a0N.jeletzyki<\/em>\u00a0and\u00a0N.haggarti\u00a0<\/em>some of the earliest octopuses, as well as some of the largest.<\/p>\n It\u2019s thought octopuses evolved from hard-shelled, squid-like ancestors that ultimately lost their shells. As other cephalopods, such as ammonites, evolved larger (and harder) shells in response to the emergence of more diverse predators during the Mesozoic Marine Revolution, octopuses decided to do the opposite, losing their shells in order to become more agile.<\/p>\n The loss of their protective shells is believed to be a key factor in the evolution of higher intelligence in octopuses. That\u2019s not to say that other, hard-shelled cephalopods aren\u2019t smart though;\u00a0cuttlefish\u00a0have solved many of the same human-set puzzles octopuses have and are known to communicate using skin colour\/pattern changes, as well as their\u00a0own form of sign language!<\/p>\nWhat group does this giant octopus belong to?<\/strong><\/h2>\n
How was this giant octopus discovered?<\/strong><\/h2>\n
Where did this giant octopus live?<\/strong><\/h2>\n
What did this giant octopus eat?<\/strong><\/h2>\n
Did anything prey on this giant octopus?<\/strong><\/h2>\n
Was this giant octopus really that big?<\/strong><\/h2>\n
When did octopuses evolve?<\/strong><\/h2>\n