| Body color | Purplish black | Variable, purple, reddish or dark green |
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| Body shape | Robust, oval, flattened | Soft, elongated, relatively high |
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| Cephalic tentacles | Short | Elongated |
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| Rhinophores | Wide apart | Close together |
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| Foot | Wide | Relatively narrow |
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| Metapodium | Very wide and broad, not developed in pedal sucker | Narrow and elongated, sometimes developed in pointed tail |
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| Parapodia | Relatively narrow, rigid, fused posteriorly | Broad, widely open, joined low down posteriorly |
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| Visceral hump | Flattened | Elevated |
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| Mantle foramen | Small, oval, flattened | Reduced, forming an elevated papilla |
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| Anal siphon | Relatively wide, very short, flattened | Wide, elongated, tubular |
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| Parapodial cavity | Reduced, enclosing the anal siphon | Widely open, exposing the anal siphon |
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| Opaline gland | With many very small openings | With a large main opening surrounded by many small secondary openings |
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| Ink gland secretion | White, scarce | Purple, copious |
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| Shell | Oval to suboval, relatively narrow, right margin narrowing abruptly towards apex | Rounded to oval, relatively wide, right margin narrowing gradually towards apex |
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| Anal sinus of shell | Wide, shallow and usually straight | Relatively narrow, deep, usually concave |
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| Jaws | Thick, longitudinal ridges well developed | Smooth, without longitudinal ridges |
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| Jaw elements | Moderately curved, with thicker tip | Slightly curved, with narrower tip |
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| m2 and m7 | Relatively thick | Relatively thin |
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| Radula | Up to 111 x 2.59.1.59.2 | Up to 67 x 2.40.1.40.2 |
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| Rachidian tooth | Central cusp lacking denticles | Central cusp with up to 2 denticles on each side |
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| Lateral teeth | Main cusp poorly serrated | Main cusp with up to 4 denticles on each side |
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| Salivary glands ducts | Thick, flattened, wider in the median portion | Thin, cylindrical, equal width along their length |
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| Gizzard plates | ~50 small plates distributed in several rows | Up to 20 small plates distributed in a single row |
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| Gastric hooks | Covering almost the entire surface of the filter chamber | Occupying a relatively narrow band in the filter chamber |
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| Digestive caecum | Tip coiled | Tip wide and flattened |
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| Intestine | Convoluted | Slightly convoluted |
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| Penial sac | Covered by spiny warts | Unarmed |
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| Penis | Thick, spatulated, covered by spiny warts | Thin, elongated, unarmed |
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| Penis tip | Bilobed | Triangular, rounded |
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| Large hermaphroditic duct | Wide, flattened, straight, strongly attached to haemocoel | Relatively narrow, cylindrical, curved, slightly attached to haemocoel |
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| Pedal nerve pd5c | Present | Absent |
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