Neither slugs nor snails: a molecular reappraisal of the gastropod family Velutinidae Author Fassio, Giulia Author Stefani, Matteo Author Russini, Valeria Author Buge, Barbara Author Bouchet, Philippe Author Treneman, Nancy Author Malaquias, Manuel António E. Author Schiaparelli, Stefano Author Modica, Maria Vittoria Author Oliverio, Marco text Zoological Journal of the Linnean Society 2023 2022-12-03 197 4 924 964 http://dx.doi.org/10.1093/zoolinnean/zlac091 journal article 10.1093/zoolinnean/zlac091 87852b6b-9e57-46bc-97af-35a7a8aee100 0024-4082 7814306 6DBA2650-DB10-4BDC-AEDB-2EF08D82815E FAMILY VELUTINIDAE GRAY, 1840 Velutinidae Gray, 1840: 90 ; type genus Velutina J. Fleming, 1820 . Included subfamilies: Hainotinae Fassio, Bouchet, Schiaparelli & Oliverio subfam. nov. , Lamellariinae d’Orbigny, 1841 , Marseniopsinae Fassio, Bouchet, Schiaparelli & Oliverio subfam. nov. , Velutininae Gray, 1840 . Description: Small to medium size for the superfamily, 0.5–11.5 cm total length. Shell exposed to completely Marseniella Uniform Norway ? Marsenia Uniform Indo-West Pacific, Mediter- ranean Sea, Caribbean Sea – 214 0 Lamellaria Uniform and Tropical Temperate eastern Pacific Tropical, Atlantic, north-eastern Atlantic, Mediterra- Sea nean, North Sea 61 0 – Coriocella Uniform Indo-West Pacific – 0 18 Djiboutia Uniform Indo-West Pacific –101 0 Pacifica Uniform Indo-West Pacific 20 – 244 Variolipallium Uniform Tropical West New, Pacific Zealand,, Caribbean South tip of, America Africa South 1573 – 42 Calyptoconcha Uniform Northern temperate, Atlantic, Sea Alboran South, Africa Uru- Brazil , guay 58 – 4500 Lamellariinae Uniform Worldwide temperate tropical, regions 4500 0 – Velutininae Scale-like elements, Arctic worldwide temperate regions 0– 1200 Hainotinae ? North-eastern, South Pacific, Australia New Zealand 0 45 –, Continued Marseniopsinae Scale-like elements Southern Ocean Argen- south tinian waters 668 75 –. Table 2 Character Composition Geograph- distri- ical bution m (Depth) Table 2. Synopsis of the most useful characters and information for diagnosis of subfamilies and genera hairy

Character	Marseniopsinae	Hainotinae	Velutininae	Lamellariinae	Calyptoconcha	Variolipallium	Pacifica	Djiboutia	Coriocella	Lamellaria	Marsenia	Marseniella
External morphology
Shape	Flat or dome	Dome shaped;	Flat or	Flat or dome	Flat or dome	Flat or dome	Flat or	Flat or	Dome	Flat or	Flat or	Flat; outline
shaped; outline	outline	dome	shaped; out-	shaped; out-	shaped; out-	dome	dome	shaped;	dome shaped;	dome	rounded
rounded or pol-	rounded or	shaped;	line rounded	line rounded	line rounded	shaped;	shaped;	outline	outline	shaped;
ygonal	polygonal	outline	or polygonal	or polygonal	outline	outline	rounded,	rounded	outline
rounded	rounded	rounded	two to six	rounded
warts
Size (cm)	0.5–11.5	0.5–5.0	0.5–11.0	0.5–10.0	1–4	0.5–3.0	0.5–1.0	0.5-3.3	1.5–8.5	0.3–1.1	0.3–10	2.2
Mantle	Fused or	Fused	Fused or	Fused or	Fused	Fused or	Fused	Fused	Fused	Fused	Fused or	Fused
dorsal fissure	not fused	dorsal fissure	dorsal fissure	dorsal fis-
sure
Shell
Shape	Ear shaped	Ear shaped	Ear, shield	Ear shaped	Ear shaped	Ear shaped	Ear	Ear shaped	Ear shaped	Ear shaped	Ear shaped	Ear shaped,
or cap	shaped	last whorl
shaped	detached
from spire
Spire	High	High	Low or	Low or high	High	High	Low	Low	Low	Low	Low or	Low
high	high
Thickness	Very thin	Thin or very	Moderately	Thin or very	Very thin	Very thin	Very thin	Thin or very	Thin	Thin	Thin	Thin
thin	thin or	thin	thin
thin
Texture	Weak to mem-	Weak	Strong to	Strong to	Weak to mem-	Weak to mem-	Weak	Weak	Strong to	Weak	Weak
	Membranbranaceous	weak	membranaceus	branaceous	branaceous	moderate	aceous
Periostracum	Thin to not vis-	Thin to mod-	Moderately	Thin to not vis-	Not visible	Not visible	Not visible	Not visible	Thin	Not visible	Not visible	?
ible	erately	or well	ible
developed,	developed,
hairy
	occasionally
Nucleous	With or without	?	With or	Subsutural	Smooth	Subsutural	Subsutural	Subsutural	Subsutural	Subsutural	Subsutural	?
granular sculp-	without	axial folds	axial folds	axial folds	axial folds	axial folds	axial folds	axial folds
ture	granular
sculpture

Table 2. Continued

Character	Marseniopsinae	Hainotinae	Velutininae	Lamellariinae	Calyptoconcha	Variolipallium	Pacifica	Djiboutia	Coriocella	Lamellaria	Marsenia	Marseniella
Radula
Formula	2:1:1:1:2	2:1:1:1:2	2:1:1:1:2	0:1:1:1:0	0:1:1:1:0	0:1:1:1:0	0:1:1:1:0	0:1:1:1:0	0:1:1:1:0	0:1:1:1:0	0:1:1:1:0	0:1:1:1:0
Rachidian	Elongated.Base	Elongated.	Squared.	Elongated.	Elong-	Elongated.	Elongated.	Elongated.	Elongated.	Elongated.	Elongated.	Elongated.
rectangular.	Base rect-	Base	Base with	ated.Base	Base bifur-	Base bi-	Base bifur-	Base bi-	Base bifur-	Base bi-	Base bi-
Cusp, three to	angular.	broad.	or without	squared.	cated.Cusp,	furcated.	cated.Cusp	furcated.	cated.Cusp,	furcated.	furcated.
four small to	Cusp, two	Cusp with	bifurcation.	Cusp, several	few to several	Cusp,	smooth,	Cusp, sev-	few to sev-	Cusp, sev-	Cusp,
sevpronounced	denticles	or without	Cusp with or	small dent-	very small to	three or	slim	eral small	eral small	eral dent-	eral
dentdenticles, each	each side	one to	without sev-	icles	pronounced	four long	denticles	denticles,	icles	icles
side	six pro-	eral denticles	denticles	denticles	right side
nounced	each side
denticles
each side
Lateral	Elongated.Cusp	Elongated.	Squared or	Elongated.Cusp	Elongated.	Elongated.	Elongated.	Elongated.	Elongated.	Elongated.	Elongated.	Elongated.
triangular,	Cusp ex-	elongated.	external, with	Cusp tri-	Cusp tri-	Cusp tri-	Cusp bold,	Cusp	Cusp bold,	Cusp tri-	Cusp
triexternal.Dent-	ternal.Dent-	Cusp tri-	or without	angular	angular	angular	smooth,	bold, ex-	external,	angular,	angular,
icles: two or	icles: one	angular,	bold, with	external.	external.	external.	external.	ternal, tri-	smooth.	external.	external.
three small to	internal; two	internal or	or without	Denticles:	Denticles: few	Denticles:	Truncated	angular.	Truncated	Denticles:	Denticles:
pronounced,	external.	external.	internal trun-	several small,	to several,	four to	projection	Denticles:	projection	several,	several,
internal; one	Denticles:	cated projec-	both sides	very small to	seven,	internal,	small,	internal, sev-	both sides	both sides
or two small to	one to six,	tion.Denticles:	pronounced,	long, both	smooth	external.	eral small
large, external	both sides	with or	both sides or	sides	Truncated	denticles,
without both	internal side	projection,	distal side
or internal	internal,
side	small
denticles,
distal side
Marginal	Narrow,	Narrow, one	Narrow,	–	–	–	–	–	–	–	–	–
smooth	small den-	with or
ticle, internal	without
side	one small
denticle,
internal
side
Jaws
Shape	Elongated	Elongated.	Short to	Short to	Short.Small,	Short to	Short.Ex-	Short	Elongated	Short to	Short to	Short
Denticles	elongated.	elongated	vertical, cen-	elongated	ternal,	elongated	elongated
Denticles	tral protru-	upper
sion	side pro-
trusion

enclosed by the mantle, thin to very thin, from strongly calcified to membranaceus; ear, shield or cap shaped, low to high spired, with expanded aperture; smooth or weakly sculptured by axial growth lines. Periostracum from thick and hairy to not visible. Protoconch of 0.76–2.10 whorls; protoconch I of 0.25–1.20 whorls, smooth or with microgranules, with or without subsutural axial folds, nucleus diameter 54–875 μm; protoconch II with or without marked axial ribs or growth lines; protoconch–teleoconch boundary not always distinct. Echinospira planktotrophic larva with double larval shell: the outer periostracal planispiral, smooth and rounded or strongly carinate, the inner helicoid. Mantle flat ( Fig. 4C ) or dome shaped ( Fig. 4A ), outline from above rounded ( Fig. 4J ) or polygonal ( Fig. 4B, H ); thick or thin, with or without dorsal warts or tubercles; with or without anterior (inhalant) and right lateral (exhalant) siphon folds; texture smooth, wrinkled, jelly-like or velvet-like; colour highly variable, almost transparent to white, grey, beige, yellow, orange, red, violet, blue, dark green, brown, black, often patterned. Penis to the right of the right cephalic tentacle; with or without a lateral subterminal papilla; with or without tip of the seminal duct protruding from the penis tip. Vas deferens with or without a free loop in haemocoel. Radula taenioglossate (with formula 2:1:1:1:2) or reduced taenioglossate (if lacking marginal teeth, formula 0:1:1:1:0); rachidian tooth base rectangular (broad or elongated) or bifurcated (inverted V-shape), rachidian cusp with or without several external denticles; lateral teeth broad or elongated, with a pointed, triangular, internal or external cusp or one external cusp plus one truncated projection, with or without denticles; marginals, when present, narrow, with or without denticles. Jaw s of v a r i a b l e s h a p e, s h o r t t o e l o n g at e d; homogeneous or composed of scale-like elements; with or without uniform masticatory denticles. Distribution: Worldwide, from shallow to abyssal waters ( 0–4500 m ). Remarks: Velutinids differ from the other two velutinoidean families ( Triviidae and Eratoidae ) chiefly in their thin to very thin, helicoid shell, with expanded aperture (vs. solid, cowry-like, with narrow aperture in triviids and eratoids) and the planispiral outer layer of the echinospira larval shell (vs. helicoid in triviids and eratoids). Also, the siphon is proportionally shorter in velutinids than in triviids and eratoids. Many velutinid species are reported to live and feed on ascidians ( Wilson, 1998 ), and the colour and texture of the dorsal mantle can mimic the ascidian host. Both hermaphroditic and gonochoristic species are reported ( Wilson, 1998 ). Egg capsules are flask shaped ( Diehl, 1956 ; Fretter & Graham, 1962 ) and are laid in holes in the tunic of the ascidians ( Peck et al. , 2006 ; Fassio et al. , 2019 ).