Vampyromorphida

{{Short description|Order of molluscs}}

{{Automatic taxobox

| fossil_range = {{fossil range|Jurassic|recent}}

| image = Vampyroteuthis illustration.jpg

| image_caption = Vampyroteuthis infernalis

| taxon = Vampyromorphida

| authority = Pickford, 1939

| subdivision_ranks = Suborders

| subdivision = ?†Kelaenina

†Prototeuthina

†Mesoteuthina

Vampyromorphina

| synonyms = *Vampyromorpha
Grimpe, 1917

}}

Vampyromorphida is an order of cephalopods comprising one known extant species (Vampyroteuthis infernalis) and many extinct taxa. Physically, they somewhat resemble octopuses (their closest relatives), but are often called vampire squids. Unlike octopuses, their eight arms are united by a web of skin, and two smaller cilia are also present.{{cite book |author= Barnes, Robert D. |year=1982 |title= Invertebrate Zoology |publisher= Holt-Saunders International |location= Philadelphia, PA|page= 461|isbn= 0-03-056747-5}} Properly speaking, the vampire squid does not possess cilia, but cirri (cilia-like projections).{{cite journal |last1=Hoving |first1=Hendrik J. T. |last2=Robison |first2=Bruce H. |title=Vampire squid: detritivores in the oxygen minimum zone |journal=Proceedings of the Royal Society B: Biological Sciences |date=22 November 2012 |volume=279 |issue=1747 |pages=4559–4567 |doi=10.1098/rspb.2012.1357 |pmid=23015627 |pmc=3479720 }} Unlike most cephalopods, which are high-energy hunters, the vampire squid has an extremely low metabolic rate. This adaptation means it requires less oxygen and its food lasts longer, helping it conserve energy and thrive in these harsh deep-sea conditions. Studies show its oxygen consumption is among the lowest of any cephalopod, allowing it to occupy a competition-free niche in the deep sea where few predators or competitors can follow, since not many can survive.Seibel, B. A., Thuesen, E. V., Childress, J. J., & Gorodezky, L. A. (1999). Decline in pelagic cephalopod metabolism with habitat depth reflects differences in locomotory efficiency. Biological Bulletin, 197(2), 207–225.