Contribution to the knowledge of European Liljeborgiidae (Crustacea, Amphipoda), with considerations on the family and its affinities

2010·19.2 MB·English

by  D'udekem D'acoz, C

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BULLETIN DE L'INSTITUT ROYAL DES SCIENCES NATURELLES DE BELGIQUE BIOLOGIE, 80: I27-259, 2010
BULLETIN VAN HET KONINKLIJK BELGISCH INSTITUUT VOOR NATUURWETENSCHAPPEN BIOLOGIE, 80: 127-259,2010
Contribution to the knowledge of European Liljeborgiidae (Crustacea,
Amphipoda), with considerations on the family and its affinities
By Cedric d'UDEKEM d'ACOZ
Abstract known MediteJTanean and North East Liljeborgiidae. It is pointed
out that the names with 'qv' introduced by G.O. SARs, like Idunella
An examination of morphological characters of the Liljeborgiidae aeqvicornis (G.O. SARS, 1877) have to retain their original spelling
reveals that these uncalceolated gammaromorphic · amphipods and that the 'qv' may not be converted into 'qu' as it is usually done
share a number of putative plesiomorphic characters with the in literature. In an appendix to the present paper, two melphidippoid
Melphidippoidea and the Oedicerotoidea. The Liljeborgiidae families, cited in literature but previously nomenclaturally invalid,
are subdivided in two subfamilies: the Idunellinae subfam. nov. are herein valided: the Cheirocratidae fam. nov. and the Hornelliidae
for Jdunella G.O. SARS, 1894 sensu lato (including Listriella fam. nov.
J.L. BARNARD, 1954) and Sextonia CHEVREUX, 1920, and the
Liljeborgiinae STEBBING, 1899 for Liljebo1gia BATE, 1862 sensu lato Key-words. Crustacea, Arnphipoda, Liljeborgiidae, Liljeborgiinae,
(including Isipingus J.L. BARNARD & KAMMAN, 1987). A list of all Idunellinae subfam. nov., Liljebotgia, LilljebOJgiella, Idunella,
known Liljeborgiidae is given. Idunella aeqvicornis (G.O. SARs, Sextonia, Cheirocratidae fam. nov., Hornelliidae fam. nov., Ew-ope,
1877) (the type species of the genus), Jdunella picta (NoRMAN, I 889) Arctic, Atlantic, Meditenanean, Systematics.
(a species partly agreeing with the characters of the genus Listriella,
which is provisionally treated as a junior synonym of Idunella) Resume
and Sextonia longirostris CHEVREUX 1920 (the most plesiomorphic
Liljeborgiidae known to date) are re-described. Jdunella proves
Un examen des caracteres morphologiques des Liljeborgiidae revele
to be morphologically very diverse but the splitting of the genus
que ces amphipodes gammaromorphes non calceoles partagent un
appears premature. Three groups are recognized within the genus
nombre impm1ant de caracteres supposes plesiomorphiques avec
Liljeborgia. Groups 1 and 2, which are cosmopolitan, speciose and
les Melphidippoidea et les Oedicerotoidea. Les Liljeborgiidae
well represented in Europe, are considered as separate subgenera:
sont subdivises en deux sous-familles: les Idunellinae subfarn.
Liljeborgia BATE, 1862 and Lilljebmgiella SCHELLENBERG, 1931.
nov. pow- Jdunella G.O. SARs, 1894 sensu lato (incluant Listriella
Group 3, which was not available for study, includes a few little
J.L. BARNARD, 1954) et Sextonia CHEVREUX, 1920 et les Liljeborgiinae
known Northwestern Pacific species and the very insufficiently
STEBBING, 1899 pour Liljebmgia BATE, 1862 sensu lata (incluant
described South African L. epistomata K.H. BARNARD, 1932
Jsipingus J.L. BARNARD & KARAMAN, 1987). Une liste de toutes les
(= Jsipingus epistomatus). The North East Atlantic and Meditenanean
especes connues de Liljeborgiidae est donnee. Une redescription
species of the subgenus Liljeborgia are revised and the following
est dmmee pour Jdunella aeqvicornis (G.O. SARS, 1877) (l'espece
taxa are separately treated: Liljeborgia brevicornis (BRUZEUUS,
type du genre), Idunella picta (NoRMAN, 1889) (nne espece dont les
1859), L. de/lava/lei STEBBING, 1906, L. inermis CHEVREUX, 1920,
caracteres coincident partiellement avec ceux de Listriella, genre
L. kinahani (BATE, 1862), L. macronyx G.O. SARs, 1894, L. mixta
provisoirement h·aite COilliTie Ul1 synonyme plus recent_d 'fdunel/a)
ScHELLENBERG, I 925, L. pal/ida (BATE, 1857), L. psaltrica KRAPP et Se.x:tonia longirostris CHEVREUX 1920 (le Liljeborgudae le plus
ScHICKEL, 1975 and Liljebotgia sp. 4. These species include the type a
plesiomorphique connu ce jour). Le genre Idunella s'avere
species of the genus Liljebmgia: L. pal/ida. Remaining difficulties
morphologiquement pa11iculierement divers mais le demembrement
to separate L. brevicornis, L. dellavallei, L. kinahani, L. mixta,
de ce demier semble premature. Trois groupes sont reconnus au sein
L. pal/ida and Liljebmgia sp. 4 are pointed out and the validity of
mihne de Liljebmgia. Les groupes 1 et 2, qui sont cosmopolites,
some of these taxa remains questionable. The rare L. inermis, which
riches en especes et bien representes dans les eaux europeennes, sont
was previously only known from Mauritania and the Cape Verde
consideres ici co1mne des sous-gemes distincts: Liljeb01gia BATE,
Islands, is now recorded from South Portugal. The close similarities
1862 et Lilljebmgiella SCHELLENBERG, 1931. Le groupe 3, qu'il n'a
between the Scandinavian upper-bathyal species Liljebmgia
pas ete possible d'etudier, comprend un petit nombre d'especes
maC/·onyx and the lower-bathyal Antarctic species L. cnephatis
peu connues du Pacifique nord occidental et l'espece sud-africaine
o'UoEKEM o'Acoz, 2008 (both eyeless species) are pointed out, and
h·es insuffisa1mnent caracterisee L. epistomata K.H. BARNARD,
it is suggested that the ancestors of L. macronyx could have lived
1932 (= Isipingus epistomatus). Les especes nord-est atlantiques et
in the Southern Ocean. In the subgenus Lilljebmgiella, Liljebmgia
mediterraneennes du sous-geme Liljeborgia sont revisees et les taxa
caliginis o'UoEKEM o'Acoz & VADER, 2009 is considered as a
suivants sont traites separement: Liljeborgia brevicornis (BRUZEuus,
probable synonym of L. chmybdis o'UoEKEM o'Acoz & VADER,
1859), L. del/aval/ei STEBBING, 1906, L. inermis CHEVREUX, 1920,
2009. An identification key and a checklist are prov1ded for all
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128 C. d'UDEKEM d'ACOZ
L. kinahani (BATE, 1862), L. macronyx G.O. SARS, 1894, L. mixta more important to try to understand to which specimens
SCHELLENBERG, 1925, L. pal/ida (BATE, 1857), L. psa/trica l<RAPP the names proposed in literature do apply than to
SCHlCKEL, 1975 et Liljeborgia sp. 4. Ces especes comprennent
speculate on the validity of pseudo-cryptic species on
l'espece type du genre Li!jeborgia: L. pallida. Les difficultes
a the basis of hard to delineate characters examined for a
eprouvees separer L. brevicornis, L. dellavallei, L. kinahani,
L. mixta, L. pal/ida et Liljeborgia sp. 4 sont soulignees et Ia validite limited number of specimens.
d'une partie de ces taxons demeure incertaine. Une espece rare, When studying the subgenus Lilljeborgiella,
L. inermis, qui n'etait precedemment connue qu'en Mauritanie et aux
o'UoEKEM o' Acoz & VADER (2009) postulated that the
lies du Cap Vert, est maintenant signalee dans le sud du Portugal. Les
occurrence of anophthalmous amphipod species in the
etroites similitudes entre Liljeborgia macronyx de Ia zone bathyale
superieure de Scandinavie et L. cnephatis o'UoEKEM o' Acoz, 2008 photic zone of Arctic and sub-Arctic seas resulted from
de Ia zone bathyale inferieure antarctique ( especes toutes les deux a colonisation of shallow seas by species of abyssal
depourvues d'yeux) sont mises en evidence, et il est suggere que origin, and they considered the possibility that the
les ancetres de L. macronyx pourraient avoir vecu dans !'Ocean
ancestors of such deep-sea species could have lived on
Austral. Dans le sous-genre Lil!jeborgie/la, Liljeb01gia ca!iginis
the continental shelf of the Southern Ocean. The same
o'UDEKEM D' Acoz & VADER, 2009 est considere com me un probable
synonyme deL. charybdis D'UoEKEM D'Acoz & VADER, 2009. Une question is considered for the subgenus Liljeborgia,
cle d' identification et une liste d' inventaire sont proposees pour with L. macronyx.
to us les Liljeborgiidae conn us de Ia Mediterranee et de I' Atlantique
Besides alphataxonomic and biogeographic aspects,
Nord Oriental. Enfin, on signale en passant que les noms avec
some higher systematic questions are briefly touched
'qv' introduits par G.O. SARS (par exemple ldunella aeqvicornis
(G.O. SARs, 1877)) doivent conserver leur orthographe originale et upon. The affinities of Liljeborgia and its relatives
que le 'qv' ne peut en aucun cas etre converti en 'qu' comme on le has been a source of continued debates over the past
fait habituellement dans Ia litterature. Dans un appendice au present 150 years, resulting in a range of conflicting and often
article, deux families de Melphidippoidea, en usage dans Ia litterature
a inconsistent proposals. The possible affinities of the
mais ce jour invalides au point de vue de Ia nomenclature, sont
Liljeborgiidae with the Melphidippoidea, suggested
validees et decrites comme «nouvelles»: les Cheirocratidae fam.
nov. et les Homelliidae fam. nov. by recent molecular data, are explored in scrutinizing
morphological data. Different generic level subdivisions
Mots-Cles. Crustacea, Amphipoda, Liljeborgiidae, Liljeborgiinae,
of the family Liljeborgiidae have been proposed in
Idunellinae subfam. nov., Liljeb01gia, Lilljeborgiel/a, ldunella,
the past, but none appear adequate. New subfamilial,
Sextonia, Cheirocratidae fam. nov., Homelliidae fam. nov., Europe,
Arctique, Atlantique, Mediterranee, Systematique. generic and subgeneric divisions are herein proposed,
and characters potentially important for further
investigations in the study of the family are pointed
Introduction out.
Finally, the comparison of the Liljeborgiidae with
The present work, which is focused on the Northeastern the Melphidippoidea obliges us to describe as 'new'
Atlantic and Mediterranean amphipods of the family two melphidippoid families, cited in literature but
Liljeborgiidae, is a follow-up of the paper by o'UoEKEM previously invalid: the Cheirocratidae fam. nov. and the
o' Acoz & VADER (2009) on the European Liljeborgia Homelliidae fam. nov.
of the subgenus Lilljeborgiella ScHELLENBERG, 1931.
Herein, the species of the second subgenus, Liljeborgia
BATE, 1862 (including the type species of the genus, L. Material and methods
pallida (BATE, 1857)) are revised. Since good quality
material of some interesting European Liljeborgiidae Complete specimens and appendages were examined in
belonging to other genera (Idunella and Sextonia) was temporary glycerin slides with a DML Leica compound
available, these species are re-described as well. An microscope equipped with a drawing tube. Pencil
identification key and a checklist are also provided for drawings were scanned and afterwards inked with the
all known Liljeborgiidae of the Nmih East Atlantic and software ADOBE ILLUSTRATOR 11.0.0 on an A3
the Mediterranean. drawing table (Wacom Intuos3 12 x 19), using the method
The subgenus Liljeborgia includes rather described by COLEMAN (2003, 2009c). Ratios are given
characteristic species likeLiljeborgia inermis CHEVREUX, to 2 decimal places, in anticipation of a future cladistic
1920, L. macronyx G.O. SARS, 1894 and L. psaltrica study, which may require various forms of rescaling.
KRArr-ScHICKEL, 1975 but also a group of ill-defined The following abbreviations are used: Al, antenna 1;
species, here designed as the group pallida. These taxa A2, antenna 2; Ep1-Ep3, epimeral plates 1-3; Gnl,
are treated separately, although the validity of some gnathopod 1; Gn2, gnathopod 2; Md, mandible; Mx1,
species is questionable. At this stage, it is considered maxilla 1; Mx2, maxilla 2; Mxp, maxilliped; P3-P7,
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European Liljeborgiidae 129
pereiopods 3-7; U1-U3, uropods 1-3. Nomenclature have to be subdivided into 'thin slender setae' and
of the setae of the mandibular palp follows LowRY & 'stout slender setae, etc) or have to be replaced by the
STODDART (1993). In the descriptions, the tenn "tooth" is acronyms SS and RS (e.g. LbRZ, et al., 2007), which
used for non-articulated, pointed ectodem1ic stJ.uctures, decreases the abstJ.·actness of descriptions. The use of the
the tem1 'acicula' for any articulated stJ.·uctme, 'spine' terms 'spine' and 'seta' in their tJ.·aditional sense seems
for stout, inflexibly articulated stJ.·uctmes (i.e. robust therefore more practical for the descriptions of species.
aciculae), the tenn 'seta' for slender, flexibly articulated LowRY & STODDART (1995: 8) also proposed to use the
stJ.uctures (i.e. slender aciculae), the tenn 'spinule' for tenn spine for the stJ.uctures traditionally called teeth
very short spines and for inflexible lateral profections of in older literature: "what we previously referred mainly
setae, and the term 'setule' for very short setae and for as teeth (non-articulating extJ.usions of the cuticle), are
flexible lateral projections of setae. now referred to as spines". This substitution is also
WATLING (1989) proposed to use of the tenn 'setae' herein rejected, firstly because it was proposed without
for any articulated stJ.ucture (including broadly conical argwnentation, and secondly because it is likely to lead
or ovoid stJ.uctures) in crustaceans, and he was followed to further tJ.·ouble for non-specialists, who largely rely
by many recent amphipodologists (e.g. ZIMMER et al., on classical literah1re (using tJ.·aditional morphological
2009). The use of a general term for any articulated nomenclahrre) for identifying their amphipods.
structure can be considered as legitimate in anatomical The following acronyms are used for scientific
or morpho-functional studies, because slender and institutions: NHM: the Natural History Museum,
robust articulated chitinous extensions are sometimes London, UK (previously British Musewn, Natural
homologous and because intennediates exist in some History); MCSN: Museo Civico di Storia Nah1rale,
cases (OSHEL & STEELE, 1988; WATLING, 1989). However Verona, Italy; RBINS: Royal Belgian Institute of
the compulsory and exclusive use of such a term in all Natural Sciences, Brussels, Belgium; TSZCr, Troms0
fields of amphipodology is not justified and coining Samlinger Zoologi Crustacea, UBZM, Universitetet i
the term 'seta' for it may have been unfortunate. The Bergen, Zoologisk Musewn.
new definition of 'seta' proposed by WATLING (1989)
conflicts both with the concept of seta used in the hwnan
language (long flexible or hair-like structure) and with Systematics
its definition in classical amphipod literature (e.g.
BARNARD & KAMMAN, 1991, p. 806: a bristle, a weakly Superfamily Liljeborgioidea STEBBING, 1899
articulated chitinous extension, which is flexible). The
current coexistence of two conflictive definitions of the CoMPOSITION: hereinrestricted tothefamily Liljeborgiidae.
tenn seta in literature has also probably become a source BoUSFIELD (1982, 1983) and BOUSFIELD & SHIH (1994)
of confusion for non-specialists, who have to identify also included the Paracrangonyctidae BousFIELD,
amphipods. This is the reason why the tenn 'acicula', 1982, the Sebidae WALKER, 1907, the Colomastigidae
plmal 'aciculae' for any articulated chitinous extension STEBBING, 1899 and the Salentinellidae BousFIELD,
is used herein. This tenn, which is the diminutive of 1977, which are specialized families strongly departing
'acus' (= needle in Latin), is not used in the English from the typical liljeborgiid body plan. A relationship
language nor in previous amphipod literature. However, between these families and the Liljeborgiidae cannot
it is used in other groups of invertebrates, and MAGENTI not be ruled out, but fwiher evidence is required before
& GARDNER (2005) defines it as 'a slender needle-like accepting this scheme.
process; a spine or a bristle; something larger than a
seta or chaeta', which complies reasonably well with
its proposed usage in amphipodology. It should also be Family Liljeborgiidae STEBBING, 1899
realized that, if an exclusive term has to be used for any
articulated structure, then a longer and more complex Family Liljeborgiidae STEBBING, 1899: 211 (type
tenninology is necessary when precise descriptions are genus: Liljeborgia BATE, 1862; type species of the type
required. So, LowRY & STODDART (1995: 8), who applied genus: Gammarus pallidus BATE, 1857)
the system of WATLING ( 1989) to alphataxonomy, used
the term 'slender setae' and 'robust setae' for the DESCRIPTION: Body elongate, laterally compressed,
struch1res traditionally named 'setae' and 'spines'. This gammaromorphic in shape.
considerably lengthens alphataxonomical descriptions Head: Eye in nom1al position, present or absent;
when fine descriptions are required ('slender setae' when present, eye usually elliptic or subquadrate,
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130 C. d'UDEKEM d'ACOZ
rarely circular; rostrum short; anterior lobe moderately Separate intennaxillar apodemes with simple medial
developed, rounded to bluntly angular, never acute; margins (at least in Liljeborgia) (COLEMAN, 2002).
antennal concavity broad and very shallow; posterior Mxp: plates and palp nonnally developed; outer
lobe obtuse and in posterior position. plate not reaching tip of article two of palp; article four
Al: equal or shorter thanA2 (very rarely longer: male of palp with distinct unguis; inner plate with 1-7 anterior
Idunella chilkensis CHILTON, 1921 ), not tmfrequently spines, which are not all clustered on anteromedial
shorter than peduncle of A2; peduncle short and stout, comer, usually without inner margino-facial spine (but
with very few spines and setae; article two of peduncle such a spine present in Idunella aeqvicornis).
slightly to significantly shorter than article one, a bit Coxae: never ventrally serrate; coxae 1-4 long to
narrower than article one; miicle three much shorier than very long; coxa 1 more or less trapezoidal and usually
article 1, usually short and stout; accessory flagellum somewhat anteriorly produced; coxae 2-3 more or less
present, well developed, with at least 2 articles, inseried quadrato-elliptic; coxae 1-3 with small posterior (and
dorsomedially; calceoli absent; callynophore absent. often small anterior) ventral notch or tooth; coxa 4 square
A2: ornamentation of peduncle variable; articles four to rectangular, almost always excavate posterodorsally,
and five of peduncle subequal; flagellum about as long often with anterovenh·al tooth, with several teeth or
as sum of articles four and five of peduncle; calceoli serrations on posterior border; venh·al margin of coxa
absent; brush of setae absent. 1-4 usually not setulose, except for seta associated with
Upper lip: short, truncate or weakly incised, anterior and posterior notch or tooth (setae arising from
symmetrical or not. medial surface can be present) [exceptionally ventral
Lower lip: soft and fragile (difficult to dissect margin of coxa 4 setulose]; coxae 1-4 of Isipingus
without damage); inner lobe scarcely developed; outer departing from usual morphology; coxae 5-7 short,
lobes ovate. sometimes with posterior denticle; coxae 5-6 subequal
Md: rectangular, with hollow part narrowly triangular and coxa 7 a bit shorter; anterior and posterior lobes of
and long; incisor process well developed and toothed; coxa 5 subequal.
left and right laciniae mobiles well developed, square, Gills: coxal gills on Gn2-P6: elliptic and simple.
flattened, and morphologically distinct; left one with 4-6 Oostegites: on Gn2-P5: very nanow, not especially
(normally 5) large teeth, and right one with medial str·ong large.
flattened tooth often posteriorly overlapping the rest of Gnathopods: subchelate, strong, similar, moderately
the lacinia (which is smooth to minutely denticulate); different or strongly different; either Gn 1 or Gn2 can be
raker spine row well developed; molar process the strongest; merus often with small acute posterodistal
variably developed: fully triturative with one posterior tooth (tooth sometimes duplicated); carpus with or
gnathobasic molar seta (genus Sextonia) or fonning a without long posterodistal process; palm well defined;
small projection with a cluster of long and stout setae outer border of palm with row of short hooked spines
(other genera); articulated with carapace with lateral or and often (especially on Gn2) with strong setae; medial
posterior hinge; palp well developed, with first miicle border of palm either with 2 indistinct rows of strong
usually long, without tooth on posterodistal comer, with setae armed with a few lateral spinules (Liljeborgiinae),
second article straight and long (longer than atiicle one or with 1 row of short stout spines and 1 row of str·ong
and article three); morphology and ornamentation of setae armed with a few lateral spinules (Idunellinae );
article three variable. dactylus of Gnl-Gn2 toothed or not; no setae in
Mx 1: left and right palps identical; palp 2-articulated, interdental notches; dactylus of Gnl without medial
second article distally not truncate, with or without setae; dactylus of Gn2 with or without medial setae;
anteromedial setae, with row of posterior/distal smooth dactylus of Gnl-Gn2 with 1 seta on anterior border, in
spines and with longitudinal row of facial setae; outer very proximal position; dactylus of Gnl-Gn2 without
plate with 7-10 strong spines, which are smooth or with distal unguis ..
short lateral denticles, never furcate; inner plate poorly P3-P4: ordinary; propodus longer or slightly shorter
setose; when there are several setae they fonn a simple than merus; dactylus either with vestigial unguis
row. associated with 2 microscopical setules (Sextonia), or
Mx2: plates elliptic subequal (inner plate very slightly without unguis and without posterior ornamentation
broader than outer plate); outer plate with posterior (other genera).
border straight or convex, with facial setae often few in P5-P7: slightly to significantly dissimilar in structure;
number, often submarginal, irregularly distributed, not morphologically basal or rather basal; P5 < P6 < P7;
fonning a row, or rarely forming an irregular row;. basis often expanded; dactylus of very variable length,
European Liljeborgiidae 131
with or without terminal unguis; dactylar ornamentation REMARKs:
reduced to 1 proximal posterior seta and sometimes 1-2
subdistal tiny anterior setules. PUTATIVE SYNAPOMORPHlES OF THE LrLJEBORGIIDAE:
Pleonites: ordinary, with or without posterodorsal The Liljeborgiidae consist of two markedly distinct
small tooth/teeth, unpaired ventrofacial spines or setae subfamilies (see further down). While the two
sometimes present (but often absent); posterior border subfamilies also share many characters, most ofthose are
of epirneral plates usually smooth, rarely serrate or either presumably plesiomorphic or widely distributed
crenulate. amongst amp hi pods, albeit not in the same combination.
Pleopods: well developed with elongate peduncle However the occurrence of long lateral spinules on the
(with 2 coupling hooks), with long rami. margino-medial setae of the palm of the gnathopods, the
Urosomite 1: with or without ventrofacial spine(s), absence of tmguis on the dactylus of the gnathopods,
with or without posterodorsal tooth or teeth; dorsal and the absence of setae (except anteroproxirnal slender
spination/setation usually absent, very reduced if seta) on the dactylus of gnathopod 1 are candidate
present. character states for synapomorphies tmiting all the
Urosomite 2: with or without posterodorsal tooth Liljeborgiidae. The fiat left lacinia mobilis with a
or teeth; dorsal spination/setation usually absent, very posterior tooth often overlapping the rest of the lacinia
reduced if present. is perhaps also a synapomorphy of the Liljeborgiidae,
Urosomite 3: with or without pair of posterodorsal but it is impossible to be certain, as the laciniae mobiles
spmes. are often inadequately illustrated (or illustrated for one
U1-U2: peduncle of U1 with several ventrofacial side only) in existing literature.
spines in Sextonia, without ventrofacial spines in other
genera; peduncle of U2 without ventrofacial spines; PREVJOUS INVESTIGATIONS ON THE SYSTEMATIC POSITION
peduncle of Ul normally with several dorsolateral OF THE LILJEBORGllDAE: The Liljeborgiidae are
spines, with 1 distal dorsomedial spine or with several uncalceolated gammaromorphic amphipods, just like
dorsomedial spines, without interramal tooth; lateral the Melphidippoidea STEBBrNG, 1899 and the Hadzioidea
distal tooth (spur) of peduncle ofU1 medium-sized, not S. KARAMAN, 1943 and are often referred to 'primitive'
more ventrolateral than dorsolateral (forming an angular in literature. Their affinities have long been debated but
discontinuity with both borders); U 1 with rami subequal; are not yet clear. After a review of earlier classificatory
U2 with outer ramus slightly shorter than inner ramus; proposals, the morphology of the Liljeborgiidae is
tip of rami either broad and spinose (Idunellinae ), or compared with that of some similar amphipods and
pointed (then tip either without spines or with trace of possible relatives.
spine fused with tip) (Liljeborgiinae). The oldest known species currently assigned to the
U3: strongly attached to urosome (never falling family Liljeborgiidae is Gammarus ? pallidus; BATE,
apart in preserved specimens, and hard to remove); 1857 (see BATE, 1857: 145). The genus Liljeborgia
peduncle medium-sized, about 2 x as long as broad; was erected by BATE (1862: 118), with Liljeborgia
rami well developed (sometimes broader and larger in pal/ida (BATE, 1857) as type species. BATE (1862) put
males than in females), most commonly subequal, with Liljeborgia in his subfamily of the 'Phoxides BATE,
tip acute (without apical spines or setae); borders of 1857' and obviously considered it as closely allied
rami always with spines (on at least one ramus), rarely to Urothoe as he compared the two genera. BATE &
with setae; outer ramus with 1 or 2 articles; the frequent WESTWOOD (1862: 206) described the speciesLiljeborgia
disappearance of the second article results from its shetlandica BATE & WESTWOOD, 1862, which turned out
fusion with the first article, not from atrophy. to be a junior synonym of Cheirocratus sundevallii
Telson: cleft and usually deeply cleft; one or several (RATHKE, 1843). Afterwards the genus Cheirocratus was
spines (sometimes associated with very short setae assigned to Gammaridae LEACH, 1814 and Melitidae
or setules) in the notch formed by the 2 apical teeth; BouSFJELD, 1973, before the 'creation' of its own family
telson without dorsal spines, but a group of 2 tiny equal Cheirocratidae by BousFIELD & SHIH (1994)1• Hence
pappose setules is sometimes observed on the surface BATE & WESTWOOD (1862) should be credited as the first
of each lobe. authors to connect Liljeborgia with Cheirocratus.
DJsTRIBUTION: Cosmopolitan, polar to tropical, 0 to 6156 1 The tenn Cheirocratidae has been introduced by BousFIELD
& SHU·I (1994), albeit without respecting the provisions of
m depth.
ICZN (1994). It is described as 'new' for validation at the end
of the present paper.
132 C. d'UDEKEM d' ACOZ
BoECK ( 1871: 154) had another opinion concerning authors. However NoTEBOOM (1986) pointed out that
the affinities of Liljeborgia (which he erroneously the Pardaliscidae could have affinities with Sensonator,
spelled Lilljeborgia with two 'L'), which he transfeiTed which exhibits some vague similarities with the
to the subfamily Leucothoime DANA, 1852. He put Liljeborgiidae.
'Cheirocratus Sundevalli' (p. 213) in the subfamily J.L. BARNARD (1969b: 291) made the following
Gamarin<I! [sic]. comments (which are not always correct) about the
STEBBTNG ( 1888) restricted the Leucothoidae (elevated affinities of the Liljeborgiidae. "In the Gammaridae only
to the rank of family) to the genus Leucothoe (p. 771) the genusParelasmopus has an elongate mandibularpalp
and Seba (p. 782), and created the family Eusiridae article 1 but its mandibular molar has a well-developed
STEBBTNG, 1888 (p. 953), to which he transfeiTed grinding surface, unlike that ofLiljeborgiidae.Apart from
Liljeborgia. (p. 980). the mandible the Liljeborgiidae are like the Gammaridae.
The idea to create a family for the genera Liljeborgia The Astyridae differs from the Liljeborgiidae by the
and ldunella was proposed by G.O. SARS (1894: overall appearance and the presence of itmer lobes or
530), who nevertheless refrained to take any fonnal a broad medial space on the lower lip. Astyt·ids have
action, retained them in the Gammaridae and treated feeble gnathopods, whereas those of liljeborgiids are
them immediately after the genus Cheirocratus in his powerfully developed. The rami of uropod 3 ofA styridae
monograph. The comments by G.O. SARs are interesting are much more elongate than those of Liljeborgiidae.
and some of them are pertinent to the present discussion. Some genera of Pleustidae have poorly developed
"The systematic position of this genus [Liljeborgia], mandibular molars as in Liljeborgiidae and the lower
established by Sp. BATE, appears somewhat doubtful.( ... ) lips are similar. Pleustids, however, have a vestigial or no
Mr. STEBBTNG, having restricted the family Leucothoidae accessory flagella and usually have tmcleft telsons, but
to the genus Leucothoe, retained the present genus one species of Austropleustes confotmds the definition.
within the remnant of BoEcK's family Leucothoidae, The Eusiridae always have the accessory flagellum
for which he proposed the name of Eusiridae. The vety 2-articulated or less and this conflicts only with the
fully developed accessory appendage of the superior genus Listriella in the Liljeborgiidae. But in contrast
antennae, as also the more or less conspicuous sexual to the Eusiridae, Listriella usually has a 2-articulated
difference in the structure of the gnathopoda, would, outer ramus of uropod 3 with an elongated atiicle 1 of
however, seem to remove this genus rather widely the mandibular palp. Eusirella and Eusiropsis are the
both from the genus Eusirus and Rhachotropis, and only eusirids having an obsolescent mandibular molar
to bring it nearer to the family Gammaridae, its and they are clearly eusirids for their possession of
species having, indeed, an unmistakable resemblance, calceoli. Eusirids have the outer ramus ofuropods 1 and
at least in external appearance, to those of the genus 2 shortened; in liljeborgiids this shortening is slightly
Cheirocratus. In the structure of the oral parts it differs, evident only on uropod 2. One genus ofA mphilochidae,
however, considerably both from this genus and the Pseudamphilochus presumably lacks an accessory
other Gammaridae, and in this respect it exhibits in fact flagellum, has a large rostrum, and nonbifid apices of
a close resemblance to the genus Leucothoe. Perhaps the telson." J.L. BARNARD & KARAMAN (1991: 413) gave
therefore, the genus should more properly be regarded a similar account, which adds little to the debate.
as the type of a separate family, and such a view is in In a new system of classification, BouSFIELD
fact suppmied by the existence of a very nearly-allied (1982, 1983) and BousFTELD & SHIH (1994) placed the
genus, Idunella, to be described below." Liljeborgiidae in the superfamily Liljeborgioidea, along
The formal, rather laconic erection of the family with the Paracrangonyctidae BousFIELD, 1982, Sebidae
Liljeborgiidae was made by STEBBTNG (1899: 211) WALKER, 1907, Colomastigidae STEBBTNG, 1899 and
and runs as follows: "Here it may be mentioned that Salentinellidae BousFIELD, 1977. While a phyletic link
I find expedient definitely to establish the family ( ...) between the Liljeborgiidae and these other families
Liljeborgiidae, in accordance with a suggestion made by (which are morphologically highly derived) cannot be
Professor SARS ('Crustacea of Norway', vol. i. p. 430) ruled out, BousFIELD did not argue convincingly. So,
to receive the genera Liljeborgia, Bate, and Idunella, JAUME eta!. (2004: 276) discuss the case of the Sebidae
Sars". and, while they recognize a superficial similarity between
DELLA VALLE (1893: 657) puts Liljeborgia in Idunella (Liljeborgiidae) and Seborgia (Sebidae) ,
synonymy with the genus Nicippe (now in the they provide sound arguments for a close relationship
Pardaliscidae BoECK, 1871 ). The possible affinity of between the Sebidae and the Leucothoidae, rather than
these two genera has not been considered by subsequent between the Sebidae and the Liljeborgiidae.
II
European Liljeborgiidae 133
BousFIELD (1982, 1983) and BousFIELD & SHIH (1994) in the cheirocratid Casco bigelowi (BLAKE, 1929)
also recognized the superfamily Melphidippoidea, both sexes cohabit in the same burrow, where mating
where they put the Cheirocratidae, the Hornelliidae2, the presumably occurs (THIEL, 1998)). To some extent,
Megaluropidae THOMAS & J.L. BARNARD, 1986 and the the Melphidippoidea could be transitional between
Melphidippidae STEBBING, 1899. With some hesitation, calceolated 'natant' amphipods and fully benthic
they also included the Phreatoganunaridae BousFIELD, uncalceolated gammaromorphic amphipods like the
1982, which is accepted neither by WILLIAMS & BARNARD Melitidae (Hadzioidea).
(1988) nor by BRE:HIER eta!. (2010). When introducing As far as is known, Liljeborgiidae have never
the name Hornelliidae, BouSFIELD & SHU-I (1994: 128), been recorded in plankton samples, but they are able
considered it as a synonym of the Cheirocratidae, but to 'move by rapid swimming' (ENEQUlST, 1949), and
this family should be understood as consisting of the are often found in the upper net (epinet) of epibenthic
genera Hornellia and Metaceradocus only. On the other sledges. So, at least some species could be swimming
hand, BousFIELD & SHlH (1994) placed the Melitidae just above the sea bottom and would not be complete
BousFIELD, 1973 (a family previously including the creepers like most Melitidae sensu lato (Melitidae and
Cheirocratidae) in the superfamily Hadzioidea. These Maeridae KRArr-ScHICKEL, 2008) and Corophioidea
actions actually refined proposals previously made by LEACH, 1814 (= Corophiidea sensu MYERS & LOWRY,
J.L. BARNARD & C.M. BARNARD (1983: 593), who 2003). In other words, they would be more benthic
discussed a loose, 'polyphyletic cheirocratid group', than the Melphidippoidea but less than the Melitidae/
which also includes the 'maerellid group' and several Maeridae and the Corophioidea.
genera with very little similarities with Cheirocratus. In her thesis on the molecular phylogeny of
The grouping of the Cheirocratidae, Hornelliidae, amp hi pods, ENGLISCH (200 1) obtained a very high
Megaluropidae and Melphidippidae seems credible support for a sister relationship between Liljeborgia and
(albeit not fully resolved) since representatives of Megaluropus (Melphidippoidea). This would suggest
these families exhibit overlapping characters. It is that the aforementioned ecological gradation could
herein accepted, but only as a working hypothesis. have a phylogenetic background. These results would
BousFIELD & SHU-I (1994) formally considered the also suggest that the old intuition of BATE & WESTWOOD
Melphidippoidea as belonging to their supposedly (1862) to relate Liljeborgia with Cheirocratus
plesiomorphic 'natant grade' (amphipods mating in the (Melphidippoidea, just like Megaluropus) should
water colwnn), although they never have calceoli, a seriously be reconsidered. On the other hand, the data
putatively plesiomorphic sensorial organ frequent in the presented in the thesis of ENG LISCH (200 1) are rather
'natants'. The plesiomorphic nature of the occurrence inconclusive conceming the systematic position of other
of calceoli is supported by the works of ENGLISCH uncalceolated gammaromorphic amphipods (Maera and
(200 1) and ENGLISCH et a!. (2003 ), who investigated Paraceradocus), which are scattered across different
the phylogeny of amphipods, using small subtmit unstable positions on her various trees (which include
rDNA gene sequences. Indeed, these authors indicate many more species than those given in the more official
that there would be a very high support for a basal publication ofENGLISCH eta!., 2003). Interestingly, they
phylogenetic position of the Oedicerotidae LILLJEBORG, also suggest that major calceolated gammaromorphic
1865 (which include some calceolated forms) amongst superfamilies (Crangonyctoidea, Gammaroidea and
amp hi pods. While the concept of'natant' versus 'reptant' Niphargoidea) are related to each others but not to
amphipods is somewhat debatable and is certainly an uncalceolated ganunaromorphic amphipods.
over-simplification, it seems reasonably applicable
in the present restricted context. The inclusion of the COMPARJSON OF THE LILJEBORG!lDAE WITH OTHER AMPHIPOD
Melphidippoidea amongst the 'natant' grade makes TAXA: The tr·aditional separation of the Liljeborgiidae
sense despite their lack of calceoli because some from other tmcalceolated ganunaromorphic amphipods
representatives of the Cheirocratidae, Megaluropidae, concerns the usual condition of the molar process
Melphidippidae (e.g. POULET et a!., 1996) and of the of their mandible, which is non-h·iturative, reduced
Hornelliidae (e.g. ALLDREDGE & KING, 1980, 1985) and is adorned with strong setae. For example,
have been found in planktonic samples (however, J.L. BARNARD (1959: 13) states "Liljeborgiid amphipods
are quite plain and "nonnal" in the sense that they
2 The tenn Hornelliidae has been introduced by Bousfield & represent the typical textbook definition and figures of
Shih (1994), albeit without respecting the provisions ofiCZN
generalized amphipods. In this respect they resemble
(1994). It is described as 'new' for validation at the end of the
the family Ganunaridae, but differ from that family
present paper.
''
134 C. d'UDEKEM d' ACOZ
principally by the mandibular structure." However, 1814 and Photidae BoECK, 1871. The posterior lobe of
this argument is not completely valid because there is the head is always blunt in the Liljeborgiidae, as in the
one known liljeborgiid species, Sextonia longirostris Megaluropidae, but it is pointed in the Homelliidae and
CHEVREUX, 1920, which has a fully triturative molar often so in the Cheirocratidae.
process (CHEVREUX, 1920b; CHEVREUX & FAGE, 1925; CALcEou: they are absent in the Liljeborgiidae and
present paper). The incorporation of Sextonia within the Melphidippoidea as in the 'maerellids', the Hadzioidea
Liljeborgiidae is justified, for in most other respects, it and in the Corophioidea. On the other hand, they are
is very similar to Idunella. present on the antenna! flagella and on the peduncle of
Ideally, affinities between Liljeborgiidae and other A2 in Sensonator.
amphipods should be established by the discovery of A 1: In Liljeborgiidae it is usually distinctly
unmistakable morphological synapomorphies with shorter than A2, sometimes equal to A2, very rarely
no trend for homoplasy (i.e. something equivalent to longer than A2 (male Idunella chilkensis CHILTON,
the fleshy telson of the Corophioidea). While in many 1921 ); A 1 is also distinctly shorter than A2 in the
respects, the morphology of ancestral amphipods Cheirocratidae, Megaluropidae, Sensonator (and in
remains debatable, it is probable that the Oedicerotoidea many Oedicerotidae). A1 and A2 are subequal in
(which obviously themselves are highly derived) are Homelliidae and Melphidippidae. On the other hand, A 1
the sister clade of all other amphipods (ENGLISCH, 2001; is norn1ally longer thanA2 in the Melitidae/Maeridae, the
ENGLISCH et a!., 2003). So, it is a priori possible that Phreatogammaridae, Crangonyctoidea, Garnn1aridoidea
this superfamily has retained unusual plesiomorphic and Niphargoidea. Article three of the A1 peduncle is
traits, and it would be judicious to compare it with the normally short and stout in Liljeborgiidae as in most
Liljeborgiidae and its potential relatives. Another point Melphidippoidea, the Phreatogammaridae, Sensonator,
to bear in mind when trying to place the Liljeborgiidae is Bathyceradocus (see J.L. BARNARD, 1961: 109-11 0;
that, amongst amphipods, evolution seems to frequently LEDOYER, 1983: 424-427) and many 'natant' families.
progress towards simplification of structures (loss or The length of article three is variable in the Melitidae/
fusion of article two of outer ramus of the third uropod, Maeridae but it is normally more slender. The accessory
loss or reduction of accessory flagellum, calceoli, setae, flagellum is always present and usually well developed
spines, teeth, etc) and it can be assumed that some losses in the Liljeborgiidae as in the Melphidippoidea and
are irreversible or at least difficult to reverse. many other gammaromorphic amphipods, but it is absent
In the different trees ofENGLISCH (2001), Liljeborgia or truly vestigial in the Oedicerotoidea (Oedicerotidae,
(Liljeborgioidea) and Megaluropus (Melphidippoidea) Exoedicerotidae J.L. BARNARD & DRUMMOND, 1982
always fonn a highly supported clade. Therefore, and Paracalliopiidae J.L. BARNARD & l<ARAMAN, 1982).
a close relationship between the Liljeborgiidae and Neither the Liljeborgiidae nor the Melphidippoidea have
the Melphidippoidea (Cheirocratidae, Hornelliidae, a callynophore, a putatively plesiomorphic structure
Megaluropidae and Melphidippidae) should (according to BousFIELD & SI-m-I, 1994) frequent in
be considered as a good hypothesis for further natant groups like the Oedicerotidae.
examination. Similarities and dissimilarities observed A2: In the Liljeborgiidae there is no setal brush. The
between the Liljeborgiidae, the Melphidippoidea, the antenna! brush of setae is a putatively plesiomorphic
supposedly basal Oedicerotidae, and sometimes other character (according to BousFIELD & SHIH, 1994)
taxa are enumerated and discussed hereafter, with the frequent in 'natant' amphipods like the Oedicerotoidea.
phylogenetic relationships suggested by ENGLISCH's In the Melphidippoidea, it has been observed in the
(200 1) trees as background. Megaluropidae (drawings by LINCOLN, 1979: 387;
HEAD: The antenna! concavity ofhead is shallow in the THOMAS & BARNARD, 1986a: 455).
Liljeborgiidae, as it is in the Hornelliidae, Megaluropidae MD (MOLAR PROCESS): With the exception of
and Melphidippidae, but it fonns a narrow slit in some Sextonia, which has a large triturative (usually
Cheirocratidae like Cheirocratus spp., as it is also the considered a plesiomorphic condition) mandibular
case in Sensonator and many Melitidae/Maeridae. The molar process with a single posterior gnathobasic seta,
anterior lobe of head is always blunt (round or bluntly the Liljeborgiidae have a reduced, non-triturative molar
angular) in the Liljeborgiidae. This is also the case in process, adorned with long and smooth strong setae (this
many Melphidippoidea, but in species like Megaluropus is usually considered an apomorphic condition). In some
agilis HOEK, 1889 and Melphidippella macra (NORMAN, representatives of other families like the Dexaminidae,
1889) it is distally pointed (with the eye in a much lower Hyperiopsidae BOYALLIUS, 1886, and Aoridae STEBBING,
position), as it is the case in some Dexaminidae LEACH, 1899 the molar process is fully triturative but its
European Liljeborgiidae 135
posterior border can be adorned with a posterior row of flattened, and often with an anterior major and minor
long setae (e.g. J.L. BARNARD, 1972a: various figures; posterior blades, but there is a paucity of data on the
ANDRES, 1977: 59; CoLEMAN & LbRZ, 2010: 35). The morphology of this lacinia in other families, preventing
same co-occunence of a triturative molar process and a systematic comparison.
molar setae was possibly also present in the ancestors Mo (PALP): The first article of the mandibular palp
of the Liljeborgiidae. In some lineages, the triturative is usually (but not always) long in the Liljeborgiidae
surface would have disappeared, while in Sextonia, and the Cheirocratidae (but not in the Homelliidae,
it was the row of setae, which would have vanished. Megaluropidae and Melphidippidae) . Interestingly, a
This is of course speculative, but there is considerable long article 1 is also observed in Maerella (KARAMAN,
evidence that such scenarios indeed happened in the 1981) and Jerbarnia (CROKER, 1971), which J.L.
Oedicerotidae, where both extreme and intermediate BARNARD & C.M. BARNARD (1983) placed in the
conditions have persisted into the modem fauna. In this 'maerellid' subgroup of their 'cheirocratids'. One or
family, most genera have a fully triturative mandible several setae on article 1 of the mandibular palp are
without posterior setae, but some have a reduced non observed in a few Liljeborgiidae (setation especially
triturative mandible with strong setae: e.g. Perioculodes important in Sextonia), some Melphidippoidea and
and Synchelidium (WATLING, 1993) and some have an Phreatogammaridae (HURLEY, 1954a) and also in the
intermediate condition with a triturative mandible 'maerellids' (CROKER, 1971; KARAMAN, 1980). The
and several posterior strong setae: e.g. Monoculodes articulation between article 1 and 2 is geniculate in the
latissimanus STEPHENSEN, 1931 (see drawings of Idtmellinae (see present paper), several Cheirocratidae
LEDOYER, 1993) and Paramonoculopsis acuta ALONSO (actually subgeniculate) and Hornellia incerta WALKER,
DE PINA, 1997 (see ALONSO DE PINA, 1997). In the 1904 (see drawings in REN, 2006), while this articulation
Melphidippoidea, the molar is fully triturative without is rectilinear in the Liljeborgiinae and the rest of the
a posterior row of long setae, but published illustrations Melphidippoidea. In a few Liljeborgiidae, article two
of some Cheirocratidae, such as Cheirocratella thori is very setose, the setae being often divided in a large
STEPHENSEN, 1940 and Casco bigelowi (see KRAPP posterolateral row and a reduced posteromedial proximal
SCHICKEL & VADER, 2002 and SHOEMAKER, 1930) and of row (e.g. Idunella aeqvicornis (G.O. SARs, 1877) and
Megaluropidae such as Megaluropus agilis HoEK, 1889 I. pirata KRAPP-SCHICKEL, 1975). It must be stated that
(see LINCOLN, 1979), suggest that the posterior border of in some Melphidippidae, like Melphidippa willemiana
the molar process bears a row of strong denticles, which o'UDEKEM o' Acoz, 2006, it is slightly curving convexly
are perhaps homologous to the long posterior setae found posteriorly and bears 2 well-developed longitudinal
in other families. However this morphological trait is rows of strong setae (see o'UoEKEM o' Acoz, 2006:
far from rare and is also observed in some Melitidae/ 492), as is frequently the case in Oedicerotidae (e.g.
Maeridae. In other words, the strongly modified molar of drawings by J.L. BARNARD, 1961; LEDOYER, 1993).
most Liljeborgiidae is by no way unique and mysterious, However such a disposition, albeit infrequent, is not
and it neither supports nor refutes the possibility of a link unique, and an article two curving convexly posteriorly
between the Liljeborgiidae and the Melphidippoidea. has been observed for example in the Pardaliscidae (e.g.
Mo (LACINIA MOBILis): In the Liljeborgiidae, HENDRYCKS & CONLAN, 2003b: 2347). Article three of
the number of teeth on the left lacinia mobilis is 5 the mandibular palp exhibits different character states
(rarely 4 or 6). This number is usually 3 or 4 in the in the Liljeborgiidae. In the putatively plesiomorphic
Melphidippoidea but 5 in Cheirocarpochela sinica REN Sextonia, it is falciform, with combed posterior setae
& ANDRES in REN, 2006 and Hornellia incerta WALKER, (D3-setae) and long isolated anteromedial setae (B3-
1904 (if the drawings of REN (2006) are conect). This setae). This disposition approaches that one observed in
number is normally 4 in the Phreatogammaridae and the Homelliidae, the Megaluropidae and the cheirocratid
the Melitidae/Maeridae, and 1 in Sensonator. BousFIELD Casco. However this condition is far from unique and
(1983) considered that a leftpentacuspate lacinia mobilis is also observed in several other groups of amphipods,
would be the plesiomorphic condition in amphipods including some Oedicerotidae.
(his opinion is not tmiversally accepted, see WILLIAMS & Mx1: In Liljeborgia (but not in other liljeborgiid
BARNARD, 1988 for instance) and he also indicated this genera), the anterior margin of the palp has one or more
is the condition observed in the Oedicerotidae. It must setae. Thjs putatively plesiomorphic character (usual in
be noticed that a pentacuspate left lacinia mobilis is also the Oedicerotidae and not uncommon in other 'natant'
observed in the Sebidae (JAUME eta!., 2009). The right families like the Eusiridae or the Ganunarellidae) is
lacinia mobilis of the Liljeborgiidae is peculiar, being rare in uncalceolated ganunaromorphic amp hi pods (e.g.
''
136 C. d'UDEK.EM d'ACOZ
not observed in the Melitidae/Maeridae sensu stricto). level character, as in theAoridae) , and especially unusual
Liljeborgia shares it with the Cheirocratidae (not with for gammaromorphic amp hip ods. In theMelphidippoidea
other Melphidippoidea) and the 'Paraceradocus/ the first gnathopod is normally smaller or subequal to
Ceradocoides group' (ANDRES, 1984; NICHOLLS, 1938). the second, but the first gnathopod is stouter than the
The setation of the inner plate of Liljeborgiidae is second in some species such as Melphidippa goesi
variable but usually reduced, as in many Oedicerotoidea STEBBrNG, 1899 (see G.O. SARs, 1890-1895, plate 169,
but unlike the Melphidippoidea and most other as M spinosa GoEs) and M willemiana (see o'UoEKEM
uncalceolated gammaromorphic amphipods, where it is D' Acoz, 2006: 493). Furthermore, a remarkable condition
well furnished with setae. is observed in Prosocratus butcheri J.L. BARNARD &
Mx2: The Liljeborgiidae are rather unusual for DRUMMOND, 1982. In this cheirocratid species the two
uncalceolated gammaromorphic amphipods in that the gnathopods are subpediform in the female (the second
facial row of the inner plate is usually absent, reduced being the largest). On the other hand, in the male the first
and if present irregular. The facial row of setae is gnathopod exhibits a grasping subchelate morphology,
well developed and regular in the Melphidippoidea being enlarged and stronger than the second gnathopod
and the Phreatogammaridae but often absent in the (J.L. BARNARD & DRUMMOND, 1982). This suggests a
Oedicerotoidea. This character is variable in the predisposition in the Melphidippoidea for an inversion
Hadzioidea. of the dominance of the gnathopods.
Mxr: The outer plate of the Melphidippoidea is rather GN1-GN2 MORPHOLOGY: In the Li!jeborgiinae, the
basal, typically with true marginal aciculae (mostly carpus is produced into a long posterior lobe. This
spines) all around the inner, distal and distolateral border, condition is not observed in the ldunellinae, although
and with innermargino-facial setae. In the Liljeborgiidae, a tiny lobe independent from the carpus is sometimes
this ornamentation is variously reduced: distolateral present (Gnl of Sextonia longirostris and of male
marginal aciculae missing in the genus Liljeborgia, and Idunella aeqvicornis). With the exception of male
either the inner marginal or the inner margino-facial Cheirocarpochela sinica (see REN, 2006), a pointed
ornamentation is missing in the Idunellinae. The inner carpal lobe is observed neither in the Melphidippoidea
plate of the Liljeborgiidae usually has no inner margino nor in other garnmaromorphic amphipods. A broad and
facial spine. In the Melphidippoidea, at least some angular carpal lobe is however commonly observed in
Melphidippidae (e.g. D'UDEKEM D'Acoz, 2006: 492 fig. the Megalmopidae. On the other hand, a long produced
1i ), Cheirocratidae ( Cheirocratus sundevallii (RATHKE, carpal lobe is observed in some 'natant' groups like many
1843), personal observation: narrowly styliform spine Oedicerotidae and some Eusiridae (e.g. Rhachotropis),
on 0.6 of inner plate) and Homelliidae (THOMAS & J.L. and also in the Leucothoidae, many Amphilochidae
BARNARD, 1986b: 479 fig. lSI, 484 fig. 4S) have such a and a few corophioids like male Erichtonius. It is not
spme. clear whether the long carpal lobe of Liljeborgia is a
GILLS AND OOSTEGITES: The Liljeborgiidae and the plesiomorphic or an apomorphic condition, due to
Melphidippoidea have slender oostegites on Gn2-P5, the patchy distribution of this character state amongst
as in the Oedicerotidae, Sensonator, and the Melitidae/ amphipods. The gnathopods are always subcheliform
Maeridae. STEELE (1990, 1991) considers slender in the Liljeborgiidae, usually subchelifonn in the
oostegites as an apomorphic character state, but his Melphidippidae and the Homelliidae (where they
main argument ( occunence of broad oostegites in non are rather weak, with a palm poorly defined), but
amphipod peracarids) is far from convincing. The shape they are often subpedifonn in the Cheirocratidae
of the oostegites is also a priori easily reversible. The and the Megaluropidae, especially in females. The
Liljeborgiidae have a simple coxal gill on the Gn2-P6, ornamentation of the dactylus is usually rather rich in
as it is the case in the Cheirocratidae, Homelliidae, the the Melphidippoidea and in some gammaromorphic
Melphidippidae and Sensonator. The Megaluropidae amphipods of tmcertain affinities like Bathyceradocus
and sometimes the Phreatogammaridae have a small gill (see DAHL, 1959: 239; LEDOYER, 1983: 426 asBenthedius)
on P7 (BousFIELD, 1982). The presence of a gill on P7 and Paraceradocus (ANDRES, 1984), where they can
is usually considered as a plesiomorphic condition and have teeth, spines and/or setae in interdental notches
is present in some Oedicerotoidea (STEELE & STEELE, and a terminal tmguis. The dactylus of gnathopods of
1991). the Melitidae/Maeridae sensu stricto is most commonly
GN1-GN2 DOMINANCE: The dominance of the first toothless, but setae and an unguis can be present. Richly
gnathopod in some Liljeborgiidae (mostly Idunellinae) ornamented dactyli of gnathopods are not unconunon
is rather unusual for amp hip ods (but this can be a family in 'natant' families (e.g. Dexaminidae) and are also