Possibly convenient octopus dichotomous key

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  1. neurobadger

    neurobadger Vampyroteuthis Registered

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    From Tolweb.

    http://tolweb.org/Octopodidae/20194

    I did not use the 'quote' function to make it easier to read.

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    The following key treats clearly defined or named genera within the family Octopodidae. The generic placement of many taxa within this family remain unresolved and are thus not covered by this key. These taxa are treated below under the general category “unplaced Octopus”. Genera designated with an asterisk (*) are in urgent need of revision.

    Notes for key:

    Male diagnostic characters: As for many other cephalopod groups, octopus taxonomy relies heavily on the reproductive charactersof mature males, particularly structures of the modified reproductive arm (hectocotylised arm). Female material is harder to identify.

    Arm lengths: Use of relative arm lengths requires intact arms. A sudden change in sucker diameter at any point along an arm is an indicator of partial arm regeneration. Such arms should not be considered in assessing relative arm lengths.

    1a Suckers in single row or as slight zigzag in live animals or contracted specimens…………………2

    1b. Suckers clearly in two rows on all arms …………………………………………………….. 13

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    2a. Ink sac present………………………………………………………………………………… 3

    2b. Ink sac absent………………………………………………………………………………… 10

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    3a. Webs greatly enlarged at distal ends to forms wing-like vanes (single species restricted to western Indian Ocean)…...………………………………………………Velodona Chun, 1915

    3b. Web margins absent or as narrow bands to arms tips, not expanded in distal portion……...… 4

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    4a. Mature males with suckers highly modified on tips of normal arms, as ridges, stellate suckers, frills of papillae or spongiform tissue; some member taxa with hectocotylised arm tip that lacks a distinct ligula and/or calamus………………………………….…………………….... 5

    4b. Mature males with distinct ligula and calamus; normal arm tips of mature males without obvious sucker modifications ……………………………………………………………...…. 6

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    5a. Hectocotylised arm tip of mature male fleshy and convoluted in the form of a walnut, no obvious calamus; distal suckers of normal arms of mature males modified into a fringe of long thin papillae (single species restricted to southern Africa)……………………………………… …………………………………………...Aphrodoctopus Roper and Mangold, 1992

    5b. Hectocotylised arm tip as normal ligula and calamus or may lack calamus; distal suckers of normal arms of mature males modified as regular ridges or as spongiform tissue… …….. …………………………………………………………………………..Eledone Leach, 1817*

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    6a. Radula normal with seven rows of teeth plus marginal plates……………………………… 7

    6b. Radula reduced to a single row of highly modified teeth with vane-like lateral wings (single species restricted to west and south-west Atlantic Ocean)………Vosseledone Palacio, 1978

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    7a. Funnel organ as W, UU or VV-shaped pads; skin smooth or sculptured ………………….. 8

    7b. Funnel organ as four distinct short longitudinal pads (IIII); all dorsal and lateral surfaces covered in large branched papillae (single species restricted to central western Atlantic Ocean)……………………………..……………………………Tetracheledone Voss, 1955

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    8a. Small to moderate species, never attaining large sizes; head width close to or greater than mantle width; gills with 6-11 lamellae per demibranch……………………………………. 9

    8b. Large (up to 14kg) species with loose soft gelatinous skin; head distinctly narrower than mantle; gills with 10-11 lamellae per demibranch (single species restricted to Antarctic waters) ……………………………………………..…………… Megaleledone Taki, 1961

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    9a. Ligula grove without transverse ridges; lower beak without sharp modified tip, rostrum curved downwards in lateral profile; posterior salivary glands approximately equal in length with buccal mass; stylets present ……………………………………… Pareledone Robson, 1932

    9b. Ligula grove with distinct transverse ridges; lower beak with sharp modified tip, rostrum straight or slightly upturned in lateral profile; posterior salivary glands approximately twice length of buccal mass; stylets absent …………………........................................................ …………………………….Adelieledone Allcock, Hochberg, Rodhouse and Thorpe, 2003

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    10a. Skin beset with raised conical or composite papillae hardened with cartilaginous inclusions (less obvious in frozen material)………………………………… Graneledone Joubin, 1918

    10b. Skin lacks hardened papillae, sculpture soft or skin completely smooth…………………. 11

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    11a. Arms short, less than 2 times mantle length; posterior salivary glands large, more than half buccal mass length………………………………………………………………………… 12

    11b. Arms of moderate length, approximately 2-3 times mantle length; posterior salivary glands small, significantly less than half buccal mass length …………Bentheledone Robson, 1932*

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    12a. Radula reduced to three to five rows of teeth; skin covered in low regular rounded papillae ………………………………………………………………..Thaumeledone Robson, 1930*

    12b. Radula complete with 7 rows of teeth, lateral teeth flattened into broad plates; skin smooth (single species known only from Tasman Sea)……………………………………………….. ……………………………..Microeledone Norman, Hochberg and Boucher-Rodoni, 2004

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    13a. Small octopuses with repeated colour pattern of iridescent blue lines or rings over body, arms and webs (markings fade to white in preserved material)…… Hapalochlaena Robson, 1929

    13b. Small to large octopuses without repeated iridescent markings over body, arms and webs (some species possess a pair of iridescent rings, one on each side of the web between the bases of arms 2 and 3)……………………………………………………………………………… 14

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    14a. Ink sac present……………………………………………………………………………….. 15

    14b. Ink sac absent……………………………………………………………………………….... 22

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    15a. Arm autotomy present, evident as multiple arms severed or regenerating from set level near to arm base (restricted to long-armed species, arms typically >4 times mantle length)….……. 16

    15b. Arm damage and regeneration not at set plane on arm (long and short-armed species)….… 17

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    16a. Third or fourth arm pair longest; large crescent-shaped markings on mantle absent; fields of enlarged suckers present on arms 2 and 3 of mature males (Indo West Pacific only) …...….....…………………...…............................................Abdopus Norman and Finn, 2001

    16b. Second arm pair longest; large crescent markings present on dorso-lateral posterior mantle; enlarged suckers absent (restricted to Central Americas only)………Euaxoctopus Voss, 1971

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    17a. Dorsal arms distinctly longer than remaining arms, arm formula 1>2>3>4 ………………... 16

    17b. Arms approximately equal in length or lateral arms longest ………………………………... 17

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    16a Series of water pores on oral web in ring around mouth, small muscular pore of each pouch opening to exterior around level of 3rd-6th proximal suckers; ligula tiny in mature males, calamus barely visible……………………………………………………Cistopus Gray, 1849

    16b. Water pouches and pores absent; ligula well-developed in mature males………………..…… ……………………………………………………………………….Callistoctopus Taki, 1964

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    17a. Ligula with transverse ligula groove containing small teeth-like lugs; raised skin ridge present on lateral mantle [single deepwater species (200-400 m) in western Pacific]…………………. …………………………………………Galeoctopus Norman, Boucher and Hochberg, 2004

    17b. Ligula groove longitudinal, without teeth-like lugs; lateral mantle ridge present or absent ... 18

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    18a. Left third arm of males hectocotylised…………………………………………….………….19

    18b. Right third arm of males hectocotylised …………………………………………………..… 20

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    19a. Mantle opening narrow, one third or less of body circumference, fitting close to funnel; paired narrow papillae over each eye; skin ridge absent from lateral mantle; body markings absent ………………………………………………………………….…Pteroctopus Fischer, 1882*

    19b. Mantle opening moderate to wide, approximately one half of body circumference; single large papilla over each eye; lateral mantle skin ridge present; two pairs of dark spots visible on mantle of live and well-preserved material………………………. Scaeurgus Troschel, 1857

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    20a. Giant species (to >4m total length); skin on mantle in loose longitudinal folds; ligula very long to accommodate giant spermatophores (up to 1 m long)……………………………………….. ……..………………………………………....Enteroctopus Rochebrune and Mabille, 1889

    20b. Small to large species; skin typically with regular or irregular patch and groove sculpture of raised patches or papillae (not in loose longitudinal folds); spermatophores small to moderate, never giant…………………………………………………………………………………… 21

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    21a. Arms typically 2-3 times mantle length; skin sculpture of dorsal mantle head and webs continues on to oral surface of shallow dorsal web; colour patterns often incorporate dark leading edges along dorso-lateral face of arms 1-3; four short longitudinal ridges of skin in diamond arrangement on dorsal mantle; stylets absent ………... Amphioctopus Fisher, 1882

    21b. Arms typically 3-5 times mantle length; sculpture on oral surface of dorsal web not a continuation of mantle and aboral web sculpture; colour patterns of dark leading arm edges absent; four large primary papillae in diamond arrangement on dorsal mantle, stylets present………………………………………………….. Octopus sensu strictu Cuvier, 1797*

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    22a. Arms extremely long, more than 6 times mantle length; arms with banded brown and white colour pattern …………………………………………………….Ameloctopus Norman, 1992

    22b. Arms short to moderate in length, less than 6 times mantle length; arms not banded ……... 23

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    23a. Skin white, lacking any pigmentation; iris of eye absent; eyes small (single species from hydrothermal vents)……………………………. Vulcanoctopus Gonzalez and Guerra, 1998

    23b. Skin with at least some pigmentation (ie oral webs, ventral and/or dorsal surfaces); iris present; eyes moderate to large ……..……………………………………………………… 24

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    24a. Calamus of mature males very large, over half ligula length (single species, southern Australia) ..................................................................................…… Grimpella Robson, 1928*

    24b. Calamus small to moderate, much less than half ligula length……………………………… 25

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    25a. Ligula of mature males large and spoon-shaped, deeply excavated with a number of well-defined transverse ridges (laminae)…………………………… Bathypolypus Grimpe, 1921

    25b. Ligula moderate to large, elongate, typically with closed ligula groove; raised laminae absent ………………………………………………………………….Benthoctopus Grimpe, 1921*

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