page_title: Cephalopod size
section_title: Notes
hierarchical_section_title: Cephalopod size / Notes
caption_attribution_description: Galiteuthis phyllura
context_page_description: Cephalopods vary enormously in size. The smallest are only about 1 centimetre long and weigh less than 1 gram at maturity, while the largest—the giant and colossal squids—can exceed 10 metres in length and weigh close to half a tonne, 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. The giant and colossal squids, for example, have the largest known eyes among living animals.
  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.
  Giant cephalopods have fascinated humankind since time immemorial.
context_section_description: The heaviest scientifically validated cephalopod specimen was a colossal squid (Mesonychoteuthis hamiltoni) weighing 495 kg (1,091 lb) (Rosa et al., 2017:1871), while hatchlings of Illex illecebrosus—some of the smallest known—have a mass of around 0.00015 g (5.3×10⁻⁶ oz) (Wood & O'Dor, 2000:93). The mass ratio between the two is .
  Comparing only adult females, the difference between the colossal squid and the pygmy squid Idiosepius thailandicus—which weighs 0.20 g (0.0071 oz) at maturity (Nabhitabhata, 1998:28)—would be .
  Wood & O'Dor (2000:93) elaborated on this mass estimate as follows:
  
  There are [...] no published weights of hatchling Nautilus spp. The weight of a hatchling N. belauensis was estimated using hatchling shell size and a regression analysis of the cubed shell diameter versus the weight of seven young N. belauensis that weighed <50 g [1.8 oz] [...] in addition to a single hatchling N. pompilius that was weighed for the present study on 24 April 1996 at the Waikiki Aquarium. The hatchling N. pompilius weighing 4.33 g [0.153 oz], with a maximum shell diameter of 26.25 mm [1.033 in], fit a highly significant correlation [...] between cubed shell diameter and weight, which indicates that a hatchling N. belauensis with a 30 mm [1.2 in] shell diameter [...] would weigh approximately 5.9 g [0.21 oz].
  Norman et al. (2002:733) wrote: "The most extreme examples of sexual size dimorphism come from marine or parasitic taxa where females are difficult to locate (Ghiselin 1974)."
  By comparison, the live weight of the largest giant clam (Tridacna gigas) specimens is estimated to be in the region of 340 kg (750 lb) (Rosewater, 1965; Knop, 1996; McClain et al., 2015), with a maximum recorded shell diameter of 136.87 cm (4.490 ft) (second among all extant molluscs with external shells only to Kuphus polythalamia at 153.2 cm (5.03 ft); Hutsell et al., 2001:142).
  Several jellyfish species may also rival the mass of the largest squid. One of the top contenders, Nomura's jellyfish (Nemopilema nomurai), grows to around 2 m (6.6 ft) in bell diameter and has a maximum wet weight of some 150–200 kg (330–440 lb) (Omori & Kitamura, 2004; Yasuda, 2004; Kawahara et al., 2006; McClain et al., 2015). Due to their very high water content, however, the dry weight of scyphomedusae is only around 4–9% of their wet weight (Larson, 1986). In squids, dry weight ranges from as much as 26% of wet weight in muscular oceanic species, to less than 9% in some ammoniacal species (see Clarke et al., 1985; Clarke & Goodall, 1994).
  Kirk (1880:312) wrote of this specimen:
  
  On 23rd of May last, the Ven. Archdeacon Stock very kindly sent me word that three boys, named Edward R. Stock, and Frank and Walter Morrah, had that morning discovered, at Lyall Bay, what they took to be a very large cuttlefish, with arms several feet long. I lost no time in proceeding to the spot, determined, if possible, to carry home the entire specimen; but judge my surprise when, on reaching the bay, I saw an animal of the size represented in the drawing now before you.* Victor Hugo's account of his "pieuvre" was brought vividly to my mind, and I could not help thinking that a man would stand but a poor chance if he once got within the grasp of such a monster.
  My first step after spreading out the arms, was to make a rough sketch and very careful measurements. I then proceeded to extract the so-called skeleton, but found that some person or persons, who had visited the spot earlier than myself, had not been able to resist the temptation to try the temper of their knives upon its back, and had in consequence severed the cuttle-bone in various places. However, I was able, not only to procure all the pieces, but also the beak, tongue, and some of the suckers, only a few of which remained, the greater portion of them having been torn off, either in some fierce encounter, or during the rough weather which had prevailed for some days previously.
  
  The length of body from tip of tail to anterior margin of the mantle was 9 feet 2 inches [2.79 m] and 7 feet 3 inches [2.21 m] in circumfere
caption: Drawing of Galiteuthis phyllura from the Bulletin of the United States Fish Commission (1881), showing the proportionately short length of the arms and tentacles
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