Cephalopods, which include squids and octopuses, vary enormously in size. The smallest are only about 1 centimetre (0.39 in) long and weigh less than 1 gram (0.035 oz) at maturity, while the giant squid can exceed 10 metres (33 ft) in length and the colossal squid can weigh almost 500 kilograms (1,100 lb) or more, making them the largest living invertebrates. Living species range in mass more than three-billion-fold, or across nine orders of magnitude, from the lightest hatchlings to the heaviest adults. Certain cephalopod species are also noted for having individual body parts of exceptional size. Cephalopods were at one time the largest of all organisms on Earth, and numerous species of comparable size to the largest present day squids are known from the fossil record, including enormous examples of ammonoids, belemnoids, nautiloids, orthoceratoids, teuthids, and vampyromorphids. In terms of mass, the largest of all known cephalopods were likely the giant shelled ammonoids and endocerid nautiloids, though perhaps still second to the largest living cephalopods when considering tissue mass alone. Cephalopods vastly larger than either giant or colossal squids have been postulated at various times. One of these was the St. Augustine Monster, a large carcass weighing several tonnes that washed ashore on the United States coast near St. Augustine, Florida, in 1896. Reanalyses in 1995 and 2004 of the original tissue samples—together with those of other similar carcasses—showed conclusively that they were all masses of the collagenous matrix of whale blubber. Giant cephalopods have fascinated humankind for ages. The earliest surviving records are perhaps those of Aristotle and Pliny the Elder, both of whom described squids of very large size. Tales of giant squid have been common among mariners since ancient times, and may have inspired the monstrous kraken of Nordic legend, said to be as large as an island and capable of engulfing and sinking any ship. Similar tentacled sea monsters are known from other parts of the globe, including the Akkorokamui of Japan and Te Wheke-a-Muturangi of New Zealand. The Lusca of the Caribbean and Scylla in Greek mythology may also derive from giant squid sightings, as might eyewitness accounts of other sea monsters such as sea serpents. Cephalopods of enormous size have featured prominently in fiction. Some of the best known examples include the giant squid from Jules Verne's 1870 novel Twenty Thousand Leagues Under the Seas and its various film adaptations; the giant octopus from the 1955 monster movie It Came from Beneath the Sea; and the giant squid from Peter Benchley's 1991 novel Beast and the TV film adaptation of the same name.
Due to its status as a charismatic megafaunal species, the giant squid has been proposed as an emblematic animal for marine invertebrate conservation. Life-sized models of the giant squid are a common sight in natural history museums around the world, and preserved specimens are much sought after for display.
Size in teuthology
Mantle length
Mantle length (ML) is the standard size measure for coleoid cephalopods (shell diameter being more common for nautiluses) and is almost universally reported in the scientific literature. The mantle is the cephalopod's "body", lying posterior to the head and enclosing the visceral mass and mantle cavity, the latter being used for locomotion by jet propulsion. Unless otherwise indicated, mantle length is measured dorsally over the midline of the mantle (sometimes specified as dorsal mantle length, DML). It is a straight-line measure, not measured over the curve of the body. In Decapodiformes (ten-limbed cephalopods), mantle length is measured from the anterior edge of the mantle (near the head), to the posterior end of the mantle or the apex of the united fins, whichever is longer. In Octopodiformes (eight-limbed cephalopods), the anterior edge of the mantle is not clearly delimited dorsally due to advanced head–mantle fusion, and mantle length is therefore taken from the midpoint between the eyes to the posterior end of the mantle. When ventral mantle length is meant instead of dorsal this is always specified as such and abbreviated VML. As an indication of overall size, mantle length is generally considered more reliable than total length because cephalopod limbs may easily be stretched beyond their natural length and are often damaged or missing in preserved specimens (this is particularly true of the long tentacles of many squid species). Nevertheless, mantle length is not equally applicable to all species. Certain benthic octopuses such as Callistoctopus ornatus are able to elongate and retract their mantles and therefore mantle length measurements, even when taken from a live specimen, may vary considerably. Another problematic case is that of the gelatinous cirroteuthids, whose weakly muscled mantles are prone to substantial shrinkage during preservation. The interocular distance may be a more reliable standard for this group.
Total length Total length (TL) is measured along the dorsal midline with the limbs outstretched and in line with the body axis. It is the greatest measurable extent of a specimen from the posterior end of the mantle or fins (or tail, if present) to the apex of the longest limb. It is recommended that arms and tentacles be measured in a relaxed state so as not to exaggerate their length, but historically this practice was not always followed and some of the more extreme published giant squid measurements have been attributed to artificial lengthening of the tentacles. Although total length is often mentioned in relation to the largest cephalopod species, it is otherwise seldom used in teuthology. As with mantle length, it is a straight-line measure. Total length is not to be confused with arm span—also known as arm spread, radial span, or radial spread—which may be much larger and is often reported for octopuses (for which the arms usually constitute the vast majority of the length). In squids, total length is inclusive of the feeding tentacles, which in some species may be longer than the mantle, head, and arms combined (chiroteuthids such as Asperoteuthis acanthoderma being a prime example). A related measure is standard length (SL), which is the combined length of the mantle, head, and arms, excluding the often long feeding tentacles. This measure is particularly useful for species such as the giant squid, where almost the entire bulk of the animal takes up less than half of its total length.
Mass Mass (often abbreviated WT for 'weight') is reported far less frequently than either mantle or total length, and accurate records do not exist for all of the large cephalopod species. It can also vary widely depending on the state of the specimen at the time of weighing (for example, whether it was measured live or dead, wet or dry, frozen or thawed, pre- or post-fixation, with or without egg mass, and so on).
Methods of size determination In contrast to the vast majority of living cephalopods, which are wholly soft-bodied, size determination of the few surviving shelled species (in terms of shell diameter) is comparatively straightforward and can be accomplished with a high level of precision. Whatever the type of cephalopod, in the absence of whole specimens, size can often be estimated from only partial remains. For example, cephalopod beaks can be used for mantle length, total length and body mass estimation, and this method has notably been used to estimate the maximum size of the colossal squid. The lower rostral length (LRL) of the beak is often used for this purpose. The rostral length of the lower and upper beaks is the standard measure of beak size in Decapodiformes; hood length is preferred for Octopodiformes. Mantle length has been estimated from video recordings of squid in the wild.
Early life stages
Hatchlings Hatchlings of Idiosepius thailandicus, possibly the smallest extant cephalopod species at maturity, have a mantle length of around 1 mm (0.039 in). The closely related Idiosepius pygmaeus weighs only 0.00033 g (1.2×10−5 oz) upon hatching and increases in weight to 0.175 g (0.0062 oz) as it reaches maturity in 50 days. Even smaller are the hatchlings of the commercially important Illex illecebrosus, with a mass of 0.00015 g (5.3×10−6 oz). Hatchlings of the giant Pacific octopus (Enteroctopus dofleini)—one of the two largest octopus species—weigh 0.0253 g (0.00089 oz) on average. At the other extreme are nautiluses, which upon hatching typically have a shell diameter of 25 mm (1 in) or more (depending on the species), the largest hatchling size among extant invertebrates. Hatchlings of Nautilus belauensis, one of the larger species, are estimated to weigh on the order of 5.9 g (0.21 oz) and mature at around 1.2 kg (2.6 lb) after almost 4000 days, or around 11 years.
Smallest adult size
The smallest adult size among living cephalopods is attained by the so-called pygmy squids, Idiosepius, and certain diminutive species of the genus Octopus, both of which weigh less than 1 gram (0.035 oz) at maturity. Idiosepius thailandicus is perhaps the smallest of all, with females averaging 10.4 mm (0.41 in) in mantle length and males 5.9 mm (0.23 in). Average wet weights are around 0.20 and 0.02 g (0.00705 and 0.00071 oz), respectively. Other tiny species include members of the bobtail squid family Sepiolidae; the myopsid squid genera Australiteuthis and Pickfordiateuthis; the oegopsid squid genera Abralia and Abraliopsis; the pygmy cuttlefish Sepia pulchra; and the ram's horn squid, Spirula spirula.
Male dwarfism The octopod superfamily Argonautoidea is characterised by markedly dwarfed males. The four extant genera of the group are Argonauta, Haliphron, Ocythoe, and Tremoctopus, all of which are exclusively pelagic. The greatest disparity in the size of the sexes is seen in the blanket octopuses of the genus Tremoctopus. Norman et al. (2002) reported a fully mature male Tremoctopus violaceus measuring 2.4 cm (0.94 in) in total length and weighing a mere 0.25 g (0.0088 oz). By comparison, the large females of this species reach total lengths of 2 m (6.6 ft) and probably some 10 kg (22 lb) in weight. This is the most extreme sexual size dimorphism known among non-microscopic animals, with mature females being at least 10,000 times heavier than males, and likely up to 40,000 times heavier. The related genera Argonauta and Ocythoe have similarly small males, but the females are not nearly as large as those of Tremoctopus, and the size dimorphism is therefore less pronounced. The females of the fourth argonautoid genus, Haliphron, are the largest of all up to length of 3.5 m (11 ft) and mass of 75 kg (165 lb) (and possibly the largest octopuses of any kind), but the males are also much larger, at up to 30 cm (12 in). So, the size dimorphism is least pronounced of all.
Extinct taxa Numerous species of so-called micromorphic ammonites are known. Maximites from the Upper Carboniferous is the smallest known ammonoid. Adult specimens reached only 10 mm (0.39 in) in shell diameter.
Maximum size
Scientifically validated records
Squids are the largest living cephalopods in terms of each of mantle length, total length, and mass, with the largest species by at least two of these measures being the colossal squid, Mesonychoteuthis hamiltoni. Reaching an estimated 3 m (9.8 ft) in mantle length and 10 m (33 ft) in total length, and weighing as much as 495 kg (1,091 lb), this species is also the largest of all extant invertebrates. The only other squid that approaches these dimensions is the giant squid of the genus Architeuthis, with females up to 275 kg (606 lb), 2.4 m (7.9 ft) in mantle length, and possibly as much as 15 m (49 ft) in total length, making it likely the longest of all cephalopods. The two largest octopus species—Enteroctopus dofleini and Haliphron atlanticus—can both exceed 70 kg (150 lb), and the former has a maximum total length of more than 6 m (20 ft). Cirrate (finned) octopods can also reach a large size, with the largest captured specimen likely being a Cirrothauma magna of 1.7 m (5.6 ft) total length and 33 cm (13 in) mantle length, though observations from submersibles suggest that members of this group can exceed 4 m (13 ft) in total length. Members of the other cephalopod groups are substantially smaller, although the largest cuttlefish can exceed 10 kg (22 lb) in weight and 50 cm (1.6 ft) in mantle length. Cephalopods of comparable size to the largest present day squid are known from fossil remains, including enormous examples of ammonoids, belemnoids, nautiloids, orthoceratoids, teuthids, and vampyromorphids.
Colossal squid (Mesonychoteuthis hamiltoni)
Though a substantial number of colossal squid (Mesonychoteuthis hamiltoni) remains have been recorded (Xavier et al., 1999 collated 188 geographical positions for whole or partial specimens caught by commercial and scientific fisheries), very few adult or subadult animals have ever been documented, making it difficult to estimate the maximum size of the species. McClain et al. (2015) stated that only 12 "complete" specimens were known. The largest known complete specimen of the colossal squid was a mature female captured in the Ross Sea in February 2007. Its weight was initially estimated at 450 kg (990 lb), its mantle length at 4 m (13 ft), and its total length at 8–10 m (26–33 ft). Once completely thawed the specimen was found to weigh 495 kg (1,091 lb), but to measure only 2.5 m (8.2 ft) in mantle length and 4.2 m (14 ft) in total length. It is likely that the specimen, and particularly its tentacles, shrank considerably post mortem as a result of dehydration, having been kept in a freezer for 14 months. (As reported by the Museum of New Zealand Te Papa Tongarewa, specimens of Nototodarus sloanii, the New Zealand arrow squid, can shrink by as much as 22% when dehydrated with alcohol solutions.) The colossal squid specimen contracted by a further 5% after several years in preservative fluid (first formalin and later propylene glycol). The fins of the 2007 Ross Sea specimen measured around 1.2 m (3.9 ft) across and it had a mantle width of 98.2 cm (3.22 ft). The arms ranged in length from 0.85 to 1.15 m (2.8 to 3.8 ft), while the two tentacles were around 2.1 m (6.9 ft) long.
Beaks recovered from sperm whale stomachs indicate the existence of animals surpassing even the 2007 Ross Sea specimen. That specimen had a lower rostral length (LRL) of 42.5 mm (1.67 in) and weighed 495 kg (1,091 lb), whereas the 300 kg (660 lb) submature female from 2003 had a LRL of 37 mm (1.5 in). By comparison, the largest known colossal squid beak from a sperm whale stomach measured 49 mm (1.9 in) in LRL. Though the number of large colossal squid specimens known to science is too small to get a good idea of the relationship between beak size and overall body size, a beak of such great size indicates a truly massive animal weighing perhaps as much as 600–700 kg (1,300–1,500 lb). However, the scaling relationship for this species shows considerable latitude, as demonstrated by a beak of 40 mm (1.6 in) LRL extracted from an animal weighing only 160 kg (350 lb).
Giant squid (Architeuthis dux)
The maximum size of the giant squid (Architeuthis dux) has long been a subject of both popular debate and academic inquiry. Unlike the colossal squid, the giant squid is known from a substantial number of mature specimens. The total number of recorded specimens (across all developmental stages) approaches a thousand, with approximately 700 documented as of 2015, of which around 460 had been measured in some way. This number has since increased substantially, with 57 specimens recorded from Japanese waters during an exceptional 15-month period between 2014 and 2015.
Based on a 40-year data set of more than 50 giant squid specimens, Roper & Shea (2013:114) suggest an average total length at maturity of 11 m (36 ft) and a "rarely encountered maximum length" of 14–15 m (46–49 ft). Of the nearly 100 specimens examined by Clyde Roper, the largest was "46 feet (14 m) long". O'Shea & Bolstad (2008) give a maximum total length of 13 m (43 ft) for females based on the examination of more than 130 specimens, measured post mortem and relaxed, as well as beaks recovered from sperm whales (which do not exceed the size of those found in the largest complete specimens). Steve O'Shea estimated the maximum total length for males at 10 m (33 ft). Older records of 18 m (59 ft) or more were likely exaggerated by stretching of the long feeding tentacles or resulted from inadequate measurement methods such as pacing. O'Shea has stated that, given the available evidence, the highest upper bound he would consider plausible for the giant squid's total length would be 15 m (49 ft), and that the likelihood that there exist 20-metre giant squid is "so exceedingly remote that you couldn't justify the effort in writing about it". Including the head and arms but excluding the tentacles (standard length, SL), the species very rarely exceeds 5 m (16 ft) according to O'Shea & Bolstad (2008). Paxton (2016a) considers 9.45 m (31.0 ft) to be the greatest reliably measured SL, based on a specimen reported by Verrill (1880a:192), and considers specimens of 10 m (33 ft) SL or more to be "very probable", but these conclusions have been criticised by giant squid experts. O'Shea (2003a) put the maximum weight of female giant squid at 275 kg (606 lb), based on the examination of some 105 specimens as well as beaks recovered from sperm whales (which do not exceed the size of those found in the largest complete specimens). Giant squid are sexually size dimorphic, with the maximum weight for males estimated at 150 kg (330 lb), though heavier specimens have occasionally been reported (such as a 190 kg (420 lb) specimen and a 163 kg (359 lb) specimen). Roper & Jereb (2010a:121) give a maximum weight of up to 500 kg (1,100 lb), and "possibly greater". Discredited weights of as much as a tonne (2,200 lb) or more are not uncommon in older literature (see below).
Other squid taxa
The third-heaviest extant squid species is Taningia danae, also known as the Dana octopus squid. The largest well documented specimen is a 160 cm ML mature female reported by Roper & Vecchione (1993) from the North Atlantic. The original paper consistently gave the mass of this specimen as 61.4 kg (135 lb), but according to Roper & Jereb (2010h:266) this figure is wrong and stems from a typographical error, the correct mass being 161.4 kg (356 lb). Another similarly large specimen—a female weighing 124 kg (273 lb)—was reported from northern Spanish waters by González et al. (2003:297) (see also initial reports). In July 2010, a sperm whale was photographed off the Azorean island of Faial with a large squid—likely T. danae—in its mouth. The specimen's maximum width, from fin tip to fin tip, was estimated at 1.5–2 m (4.9–6.6 ft); this would approximate its mantle length.
Onykia robusta, previously known as Moroteuthis robusta and sometimes called the robust clubhook squid, has a mantle length of up to 200 cm (6.6 ft). Some older records exceed this, such as the 91.5 in (232 cm) ML reported by Verrill (1876:237) from a specimen with a total length of 14 ft (4.3 m) (excluding the ends of the tentacles, which had been destroyed). Nesis (1987:192) likewise gave a maximum mantle length of 230 cm (7.5 ft), but Roper & Jereb (2010i:364) wrote that "this old record might be in error", with the species commonly growing to 160 cm (5.2 ft) ML. Glaubrecht & Salcedo-Vargas (2004:66) provided a maximum total length of 4–6 m (13–20 ft). Literature sources give a maximum weight of 50 kg (110 lb). There exist numerous published records of large individuals of this species.
The Humboldt squid (Dosidicus gigas), also known as the 'jumbo squid', grows to a maximum mantle length of at least 120 cm (3.9 ft), if not 150 cm (4.9 ft). The largest animals are found off the western coast of South America; northern populations reach 100 cm (3.3 ft) ML, and in general 50–80 cm (1.6–2.6 ft) ML is more typical for the species. Southern populations may have a total length approaching 2.5 m (8.2 ft), and possibly up to 3.7 m (12 ft). Again, specimens from the Northern Hemisphere are much smaller, with those off the Californian coast reaching total lengths of less than 1.7 m (5.6 ft). The Humboldt squid commonly attains a weight of around 20–30 kg (44–66 lb) and can reach a maximum of 50 kg (110 lb). There are anecdotal reports of much larger individual animals, including from diver Scott Cassell, who has dived with Humboldt squid over 300 times (reportedly more than any other person). Moroteuthopsis longimana, previously Kondakovia longimana and sometimes known as the giant warty squid, is a little known species with a circum-Antarctic distribution in the Southern Ocean. The largest complete specimen, found floating at the surface off the South Orkney Islands, had a mantle length of 108 cm (3.54 ft), but a damaged female specimen with an estimated mantle length of around 150 cm (4.9 ft) is known. The largest complete specimen had a wet weight of 29 kg (64 lb). The species' maximum weight has been estimated at 50 kg (110 lb).
Largest octopodes
The giant Pacific octopus (Enteroctopus dofleini) grows to more than 6.1 m (20 ft) in total length and at least 60 cm (2.0 ft) in mantle length. Cosgrove (1987) and Cosgrove & McDaniel (2009:69) gave a maximum confirmed weight of 71 kg (157 lb) for a live specimen collected in the mid-1960s. Norman et al. (2014:124) accept a maximum weight of at least 180 kg (400 lb), which approximates the 182.3 kg (402 lb) reported for a specimen caught off Santa Barbara, California, in 1945, of which photographic evidence survives. No specimens approaching this size have been reported since the middle of the 20th century, with recent specimens very rarely exceeding 50 kg (110 lb). It is possible that the maximum size of the species has decreased over this period, perhaps due to bioaccumulation of toxicants (see below). In 2002, a giant specimen of Haliphron atlanticus, the seven-arm octopus, was caught by fishermen trawling at a depth of 920 m (3,020 ft) off the eastern Chatham Rise, New Zealand. This specimen, the largest of this species and possibly of all octopuses, was the first validated record of Haliphron from the South Pacific. It had a mantle length of 0.69 m (2.3 ft), a total length of 2.90 m (9.5 ft), and a weight of 61.0 kg (134.5 lb), although it was incomplete. The total length of the specimen, when complete, has been estimated at 4 m (13 ft), and its weight at 75 kg (165 lb).
Extinct taxa
Certain extinct cephalopods rivalled or even exceeded the size of the largest living species. In particular, the subclass Ammonoidea is known to have included a considerable number of species that may be considered "giant" (defined by Stevens, 1988 as those exceeding 1 m (3.3 ft) in shell diameter). The largest confirmed ammonite, a specimen of Parapuzosia seppenradensis discovered in a German quarry in 1895, measures 1.742 m (5.72 ft) in diameter, though its living chamber is largely missing. The diameter of the complete shell has been estimated at 2.55 m (8.4 ft), assuming the living chamber took up one-fourth of the outer whorl. Teichert & Kummel (1960:6) suggested an even larger original shell diameter of around 3.5 m (11 ft) for this specimen, assuming the body chamber extended for three-fourths to one full whorl. In 1971 a portion of an ammonite possibly surpassing this specimen was reportedly found in a brickyard in Bottrop, western Germany. A specimen found by Jim Rockwood, from the Late Triassic near Williston Lake, British Columbia, was said to measure more than 8 ft (2.4 m) across, but was later determined to be a concretion.
Heteromorph ammonites are known to have exceeded 1 m (3.3 ft) in length also, but since their shells were uncoiled to varying degrees, they were overall much smaller than the largest non-heteromorphs. The greatest lengths of all were reached by the orthocones of endocerid nautiloids such as Endoceras, which may have exceeded 8 m (26 ft), although their maximum size is uncertain; while the largest well documented endocerid fossil is likely the 3-metre-long (9.8 ft) shell fragment housed at the Museum of Comparative Zoology, Harvard University, there are published reports of even larger specimens. Teichert (1927) mentioned specimens up to 5 m (16 ft) long from the Middle Ordovician limestone of Estonia and Frey (1995:72) gave a maximum shell length of 6 m (20 ft) for the group. On the subject of endocerid size, nautiloid specialist Rousseau H. Flower wrote:
They are not all large, by any means, but specimens twelve feet [3.7 m] in length have been collected, and fragments of greater diameter indicate a much greater maximum length. I am not wholly inclined to discredit a report of an endoceroid found in a quarry near Watertown New York, which was measured before it was broken up and found to attain a length of 30 feet [9.1 m]. However, the uncoiled length of the largest ammonites far exceeds that of even these giant endocerids. Parapuzosia seppenradensis, the largest known ammonite species, had an estimated maximum unrolled shell length of around 18 m (60 ft). It was also possibly the heaviest of all known cephalopods, past or present, with an estimated live mass of 1,456 kg (3,210 lb), of which the shell would constitute 705 kg. By comparison, the largest endocerids may have weighed around 1,000 kg (2,200 lb). In terms of mass, these are the largest known invertebrates that have ever lived, though perhaps still second to the largest living cephalopods when considering tissue mass alone, since in shell-bearing species the vast majority of the living tissue is restricted to the body chamber, which occupies only a fraction of the internal shell volume. They might also be the largest—or at least longest—shell-bearing animals that have ever lived. Cretaceous Yezo Group in Japan yields multiple taxa of large-sized cephalopod fossil remains. Oegopsid Yezoteuthis giganteus and Haboroteuthis poseidon are only known from jaw elements, which is close to size of that of giant squid. Species of Nanaimoteuthis, especially N. hikidai would be the largest known vampyromorph. Unnamed, incomplete upper jaw fossil that is approximately twice as large as that of the mature giant squid is also found there. In 2026, Nanaimoteuthis haggarti was estimated to be between 7 and 19 m long, making it possibly the largest animal in the Late Cretaceous oceans and even the largest known invertebrate. Though the upper estimates of its body length have been questioned by some researchers.
Historical claims
Misidentifications
The maximum sizes of certain cephalopod species, most notably the giant squid and giant Pacific octopus, have often been misreported and exaggerated. The literature on cephalopod size has been further muddied by the frequent misattribution of various squid specimens to the giant squid genus Architeuthis, often based solely on their large size. In the academic literature alone, such misidentifications encompass at least the oegopsid families Chiroteuthidae, Cranchiidae, Ommastrephidae, Onychoteuthidae, and Psychroteuthidae. This situation is further confused by the occasional usage of the common name 'giant squid' in reference to large squids of other genera. Perhaps the most notable misidentification relates to a photograph taken some time before 1993 by diver H. Kubota off southern Japan. The image shows a large individual of Onykia robusta (previously known as Moroteuthis robusta), which appears to be sick or dying, alongside a diver in shallow water. A video of the same animal appeared in a Japanese made-for-television film. The image was published in the 1993 book European Seashells by Guido T. Poppe and Yoshihiro Goto, where it was identified as Architeuthis dux, the giant squid, and said to have been taken in the North Atlantic. If true, this image would represent the first known photograph of a live giant squid. In The Search for the Giant Squid (1998), Richard Ellis wrote:
For a moment, I thought that some obscure photograph had captured the most elusive image in natural history. Fortunately for those who have devoted their lives to searching for Architeuthis, this was only an aberration, a case of mistaken identity. It would be more than a decade before the true first photographs of a live giant squid in the wild were taken on 30 September 2004 by Tsunemi Kubodera and Kyoichi Mori. Kubodera and his team subsequently became the first to film a live adult giant squid on 4 December 2006, and the first to film a live giant squid in its natural habitat in July 2012. These milestones were preceded by the first footage of a live (paralarval) giant squid in 2001, and the first image of a live adult giant squid on 15 January 2002. Since then, live giant squid have been photographed and filmed on a number of occasions.
Giant squid
Reports of giant squid (Architeuthis dux) specimens reaching or even exceeding 18 m (59 ft) in total length are widespread, but no animals approaching this size have been scientifically documented in recent times. This is despite there being hundreds of specimens available for study (c. 700 documented as of 2015, of which c. 460 measured in some way), including numerous recent examples, such as the 57 specimens recorded from Japanese waters over a 15-month period in 2014–2015. It is now thought likely that such lengths were achieved by great lengthening of the two long feeding tentacles, analogous to stretching elastic bands, or resulted from inadequate measurement methods such as pacing. On the subject of the oft-cited maximum size of 18 metres—or 60 feet—Dery (2013) quoted giant squid experts Steve O'Shea and Clyde Roper:
If this figure [45 ft or 14 m] seems a little short of the Brobdingnagian claims made for Architeuthis in most pop-science stories about the animal, that's probably because virtually every general-interest article dutifully repeats the magic number of 60 feet. Steve O'Shea deplores the media's perpetuation of what he believes to be a credulity-straining exaggeration, based on the 19th-century biologist Thomas Kirk's eyeball estimate of a specimen's length. In a comment on the final draft of this article, O'Shea wrote, "Kirk paced it, in his own words, for he had no ruler/measure handy, and I believe this misrepresentation has been perpetuated enough; if they were foot-on-foot, as in heel directly to toe, I would accept 57 (or 58, whatever the precise figure was), but I think perpetuating this as fact any longer is doing a disservice to science."
Roper, in his comments on the final draft of this article, was even more conservative, writing, "there are no confirmed records of giant squid longer than about 45 feet [14 m] total length. Most are in the 25–35-foot [7.6–10.7 m] range. I have examined specimens in museums and laboratories around the world—perhaps a 100 or so—and I believe the 60-foot number comes from fear, fantasy, and pulling the highly elastic tentacles out to the near breaking point when they are measured on the shore or on deck."
Largest reported animals
Paxton (2016a) investigated the maximum size of Architeuthis by performing a statistical analysis using data from literature records of giant squid specimens. He selected what he regarded as the largest size records for each of mantle length (ML), standard length (SL), and total length (TL). Paxton's study has been criticised by giant squid experts, who have called into question the reliability of some of the selected literature records. For mantle length, Paxton (2016a:83) considered the 11 ft (3.35 m) reported by Dell (1952:98) as the "longest measured", though "more reliably" the 9 ft 2 in (2.79 m) ML specimen from Lyall Bay, New Zealand, documented by Kirk (1880:312). Paxton added: "A 4.5 m [15 ft] specimen from Mauritius is often mistakenly cited but consultation of the primary paper (Staub, 1993) reveals an ill-defined length which is clearly not ML." The greatest measured ML of a giant squid recovered from a sperm whale is either the 2.4 m (7.9 ft) reported by Keil (1963:320) (though Paxton writes: "the account is confused and the 2.4 m figure probably refers to the head and ML combined") or the 6 ft 6 in (1.98 m) of a specimen that had been swallowed whole off the Azores, detailed by Clarke (1955:589) and Clarke (1956:257). The "longest visually estimated" ML, according to Paxton, is the c. 100 ft (30 m) of a specimen apparently observed in the North Atlantic off Portugal, attributed to a personal communication with T. Lipington. A more modest 4 m (13 ft) ML is also given, based on a sighting in the Indian Ocean sourced to the TV documentary of Lynch (2013). For standard length (excluding the tentacles), Paxton (2016a:83) cited the 31 ft (9.45 m) of the "Three Arms specimen" documented by Verrill (1880a:192) as the "longest measured". Among specimens recovered from sperm whales, the longest "definitely measured" SL is the 16 ft 3 in (4.95 m) reported by Clarke (1956:257) and the longest "visually estimated" SL is the c. 9 m (30 ft) attributed to a photograph of a sperm whale with giant squid remains in its jaws, though Paxton conceded that it is "[n]ot clear how much/what portion of body was eaten". For the "longest visually estimated", more extreme supposed SLs of c. 175 ft (53 m) and c. 100 ft (30 m) are cited to Starkey (1963) and Ellis (1998a:246), respectively (the latter an eyewitness account by Dennis Braun). Paxton treated these last two size estimates as SLs as opposed to TLs because "squid do not generally leave their tentacles exposed except when grabbing prey and this appears to be the case for Architeuthis". For total length, Paxton (2016a:83) considered three records as candidates for the "longest measured": the 19 m (62 ft) specimen of Berzin (1972:199), the 55 ft 2 in (16.81 m) specimen described by Kirk (1888) as Architeuthis longimanus—a strangely proportioned animal that has been much commented on—and the 55 ft (16.76 m) "Thimble Tickle specimen" reported by Verrill (1880a:191), which is often cited as the largest giant squid ever recorded. Of the last one, Paxton wrote: "Sometimes mistakenly cited as 17.37 m (57.0 ft) but the source is clear that it is 55 ft long." The first two records, particularly that of Berzin, are more questionable, as Paxton explained:
The accuracy of the two longest measured TLs of 19 and 16.81 m from a specimen found in the gut of a sperm whale from the Indian Ocean and from the specimen from New Zealand in 1887, respectively, should also be questioned but again are certainly not impossible. The New Zealand specimen (named Architeuthis longimanus Kirk, 1888) clearly has the largest ratio of TL to ML ever known in Architeuthis [...] which led [O'Shea & Bolstad, 2008] to suggest that the length was paced out and/or there was extensive post-mortem stretching. However, a re-reading of the original paper suggests that the specimen, although initially paced out, was actually measured, nevertheless the TL is at the edge of the 99.9% prediction interval range [...] and so it was certainly an unusual specimen. Berzin's (1972) Indian Ocean claim is suspect because of the roundness of the figure, the lack of detailed measurements and because in an associated photo, the mantle (whose length was not given) does not look very large compared to the men in the image. Consequently the measurement, if accurate, would represent another animal with very long tentacles.
However, as Paxton (2016a:86) pointed out, the genetic analysis of Winkelmann et al. (2013)—which concluded that there is likely a single, globally-distributed species of Architeuthis—did not encompass these two specimens, and it is therefore possible that there exists a second, as yet unsampled, giant squid species with proportionately longer tentacles. The 19 m (62 ft) total length of the Berzin specimen was later confirmed to be erroneous; according to Valentin Yukhov, who was involved in the specimen's discovery, it should have read 9 m (30 ft). The misprint was reproduced in the English translation published the following year and was later propagated in a number of papers on giant squid. With the Berzin specimen not being as large as originally reported, the longest giant squid recovered from a sperm whale is the 34 ft 5 in (10.49 m) TL individual recorded by Clarke (1956:257) (this specimen also has the longest confirmed ML and SL of any giant squid from a sperm whale). Paxton considered the "longest visually estimated" TL to be the 60 ft (18 m) published by Murray (1874:121), from an eyewitness account by fisherman Theophilus Picot, who claimed to have struck the floating animal from his boat, causing it to attack. Picot managed to hack off one of its tentacles, which was subsequently examined by a number of authors. Perhaps the largest of all recorded giant squid specimens was the one found floating at the surface off Saint-Gilles, Réunion, on 4 March 2016. Although due to its great size the specimen could not be retrieved in its entirety, the head and arm crown were saved. Crucially, this meant the beak could be measured to estimate the mantle length and total length of the specimen. Using different allometric scaling equations, the lower rostral length of the beak, at 19.74 mm (0.777 in), gave an estimated dorsal mantle length of 215.3–306.0 cm (7.064–10.039 ft) and this, in turn, was used to estimate the total length at 11.025–15.664 m (36.17–51.39 ft).
Supposed sucker scars
More extreme and outlandish giant squid size claims—belonging firmly in the realm of cryptozoology—have appeared in the works of authors such as Bernard Heuvelmans, Willy Ley, and Ivan T. Sanderson. The existence of these gargantuan squids is often supported by reference to the giant circular scars sometimes found on sperm whales, which are assumed to have been inflicted by the suckers of struggling giant squid. Sometimes these claims are accompanied by extrapolations of body size based on the isometric upscaling of a "typical" giant squid. However, such scars are not necessarily of squid origin and may instead represent fungal growths or bite marks, with sea lampreys (Petromyzon marinus) being one possible source. Even in the case of genuine giant squid sucker marks it is possible that subsequent skin growth has enlarged them well beyond their original dimensions.
Nevertheless, claims of enormous sucker scars are widespread in the literature. Richard Ellis collected some of "the more egregious examples" in his book, The Search for the Giant Squid. These include the claim of Dozier (1976) that "an ordinary giant squid of 50 feet [15 m] leaves teeth-ringed sucker marks measuring between three and four inches [7.6–10.2 cm] across on a whale, but sperm whales have been captured with tentacle marks 18 inches [46 cm] across." L. Harrison Matthews's monographic treatment of the sperm whale, published in 1938, includes the following: "Nearly all male Sperm whales carry scars caused by the suckers and claws of large squids, scars caused by suckers up to 10 cm. [3.9 in] in diameter being common. The claw marks take the form of scratches 2–3 m. [6.6–9.8 ft] in length, and appear to be of more frequent occurrence than sucker marks". Ellis (1998a:142) wrote that this 10 cm figure is "so much larger than any other recorded sucker dimensions that one suspects some sort of error, either in measuring or in transcription." The subject was covered in some detail by Wood (1982:192):
Measurements of 90 ft [27 m], 130 ft [40 m] and even 200 ft [61 m] have been conjectured for giant squids from the size of sucker marks found on the skins of captured sperm whales, but it is dangerous to place too much relianc