Contr. Tert. Quatern. Geol. 36(1-4) 45-57 2 tabs, 2 pis. Leiden, December 1999
Neogene species of Pseudamussium
(Mollusca, Bivalvia, Pectinidae)
from Belgium
R. Marquet
Antwerp, Belgium
and
H.H. Dijkstra
University of Amsterdam
Amsterdam, the Netherlands
Marquet, R. & H.H. Dijkstra. Neogene species ofPseudamussium (Mollusca, Bivalvia, Pectinidae) from Belgium. — Contr. Tert.
Quatern. Geol., 36(1-4): 45-57, 2 tabs, 2 pis. Leiden, December 1999.
The and differences between this and Palliolum status of the pectinid genus Pseudamussium Mörch, 1853 is discussed, taxon
Monterosato, 1884 are outlined. Five species from the Neogene of Belgium are assigned to Pseudamussium, viz. P. princeps (J. de C.
Sowerby, 1826), P. edegemense (Glibert, 1945), P. lilli (Pusch, 1837), P. sulcatum (Müller, 1776), and P. clavatum (Poli, 1795). All
of these described and and their and here are illustrated, stratigraphic ranges palaeoecology discussed. Pseudamussium sulcatum is
the P. The latter and Pecten recorded from the Belgian Pliocene for first time, as is lilli. species’ wide range of variation is discussed
scissus 1869 is considered be The of P. between the Favre, to a junior synonym. stratigraphic distribution lilli suggests a connection
and the left valve of North Sea Basin and the Paratethys during the Miocene. In addition, the ontogeny of P. princeps is described, P. edegemense is here illustrated for the first time.
Key words — Bivalvia, Pectinidae, Neogene, North Sea Basin, taxonomy.
R. Marquet, Constitutiestraat 50, B-2060 Antwerpen, Belgium; H.H. Dijkstra, Department of Malacology, Zoological Museum,
University of Amsterdam, P.O. Box 94766, NL-1090 GT Amsterdam, the Netherlands [e-mail: [email protected]].
Contents cavations, at the construction of a water purification
the under- plant near Schijnpoort, Antwerp, at Antwerp
Introduction 45 construction at and p. ground pits, Schijnpoort Schoolplein,
Systematic descriptions p. 46 at building sites in the Ploegstraat, Antwerp, as well as
Acknowledgements p. 51 during temporary excavations at Zonderschot (Heist-op-
the References p. 51 den-Berg, southeast of Antwerp) by Belgische Ver-
eniging voor Paleontologie (BVP). Papers on (tempo-
rary) sections and their biostratigraphic interpretation
Introduction include those by De Meuter et al. (1967, 1976), Janssen
& Van der Mark (1969), Marquet (1991) and Hooy-
but the molluscan faunas collected at Many new data on Neogene faunas from northwest Bel- berghs (1996a, b),
these localities have not yet been studied in detail. Plio- gium have been assembled during the past thirty years,
and cene faunas collected at the harbour works at numerous molluscan species have been recorded for gastropod have the first time for the North Sea Basin. In addition, certain Kallo (west of Antwerp, Oost-Vlaanderen) recently
been described 1993, species identifications could be amended, since the new by Marquet (1984, 1995a, 1996,
collections and comprised much more and better-preserved 1997a-c) monographed by Marquet (1998).
material. The present paper is the third in a series of contri-
Miocene faunas have been extensively collected dur- butions revising Neogene bivalves collected at Kallo and
ing construction works of the Kleine Ring (E3) motor- at other recent temporary outcrops, the first being those
and way around Antwerp, at the Kennedy Tunnel ex- by Dijkstra & Janssen (1988) Marquet (1995b). 46
SYSTEMATICDESCRIPTIONS secondary radial macro-ornament, rarely intercostal
smooth commarginal ornament. Internal surface or lyrate,
size. Ctenolium delicate Abbreviations — To denote the repositories of speci- not carinate. Auricles unequal in
mentioned in the abbreviations with teeth; notch shal- mens text, the following closely spaced byssal moderately
- - low and fasciole rather are used: HD H.H. Dijkstra Collection, IRScNB In- throughout ontogeny, byssal
stitut royal des Sciences naturelles de Belgique, Brussels broad.
— Mid- (Belgium), RGM - Nationaal Natuurhistorisch Mu- Distribution Early Miocene to Recent, Europe;
seum/Naturalis, Leiden (the Netherlands, formerly dle Miocene, Iran; Recent, eastern Pacific (see Hertlein
- in Rijksmuseum van Geologie en Mineralogie), RM R. Moore, 1969, p. N354).
— references Pseuda- Marquet Collection. Remarks Numerous previous to
mussium may be found in Grau (1959), who followed
mainly North (1951a, b). Hertlein in Moore (1969, p.
Order Ostreoida Ferussac, 1822 (emend. N354) placed Pseudamussium in the Eburneopecten
Waller, 1978) group, together with Cyclopecten Verrill, 1897, Hemi- Palliolum Suborder Pectinina Waller, 1978 pecten Adams & Reeve, 1849 and Montero-
1884 and number of Superfamily Pectinoidea Wilkes, 1810 (emend. sato, a subgenera. Subsequently,
Waller, 1978) Vaught in Abbott & Boss (1989, p. 119) in part followed
Family Pectinidae Wilkes, 1810 (emend. Hertlein and assigned Pseudamussium to the tribe
Waller, 1978) Eburneopectini, which also included Delectopecten
Subfamily Palliolinae Korobkov in Eberzin, 1960 Stewart, 1930. Cyclopecten, however, is a propeamussiid Waller Tribe Palliolini Waller, 1993 (= Palliolum genus, not a pectinid, according to (1984, p. 213). The resembles Pedum Lamarck, group, Waller in Shumway, 1991) monotypic Hemipecten
1799 Waller, 1972, and is now referred to Genus Pseudamussium Morch, 1853 (see p. 256)
the tribe Chlamydini von Teppner, 1922 (see Waller,
and 1993, p. 200). With Placopecten Verrill, 1897 Pseu-
damussium, Palliolum the Palliolum Type species — Pecten septemradiatus Miiller, 1776 (= belongs to group, referred the tribe Palliolini Ostrea Linne, 1771; see 1999, now to as (see Waller, 1993, peslutrae Dijkstra, p. 427)
under the 198). Waller & Marincovich (1992, 219) have re- plenary powers (ICNZ Opinion 714). p. p.
Stratigraphic distribution— Early Miocene to Recent. cently placed Delectopecten in the Camptonectinae and show — 1977. Synonyms The following taxa are considered to be Habe, Peplum Karnekampia mor-
features identical to those of Pseudamussium synonymous with Pseudamussium: phological
and here considered to be thus are junior synonyms (see
Pseudamusium 134 also Hertlein in Waller in Shum- -J Klein, 1753, p. (pre-Linnaean); Moore, 1969, p. N355;
Pseudamussium 340 -1 Herrmannsen, 1847, p. (nomen nudum); way, 1991, p. 35). Neogene species from the North Sea
Pseudamussium H. & A. Adams, 1853, 553 of -J p. (subgenus Basin have formerly been assigned either to Palliolum or
Pecten), type species, by subsequent designation of Dall, 1898 these to Pseudamussium; differences between taxa are (p. 751), is Ostrea hybrida Gmelin, 1791 (= Ostrea exotica briefly outlined in Table 1. Dillwyn, 1817);
Pseudamusium Verrill, 1897, 60 of Pseuda- -i p. (emendation
mussium H. & A. Adams);
-l et 67 Pseudamussium edegemense (Glibert, 1945) Peplum Bucquoy al., 1889, pp. 62, (subgenus of
Pecten), type species, by original designation, (= Ostrea PI. 1, figs 3, 4
clavata Poli, 1795);
191 of * Platipecten-i Monterosato, 1889, p. (subgenus 1945 Pecten (Pallium) edegemensis Glibert, p. 77, pi. 3,
Chlamys), type species by original designation, is Pecten fig. 3a-c.
subclavatus Cantraine, 1835 (= Pecten septemradiatus Midler,
1776); Locus typicus — Former clay pit at Edegem, south of -J in 9 ICNZ Porosichlamys Barsotti Lucas, 1979, p. (invalid, Antwerp, Belgium. art. lie);
Stratum — Berchem -I typicum Formation, Edegem Karnekampia Wagner, 1988, p. 41, type species, by original Member designation, is Pecten bruei Payraudeau, 1826 (= Pecten (Miocene, Hemmoorian, Behrendorfian).
sulcatus Miiller, 1776). Material studied — IRScNB 1ST 1943 (holotype),
IRScNB 1ST 1944, IRScNB 1ST 6384, IRScNB 1ST
Diagnosis — Radially undulated to smooth Palliolini 6394, in addition to 1 specimen (RM Colin, temporary
Gaumont Cinema, Berchem with antimarginal micro-ornament on anterior and pos- outcrop garage Antwerp,
terior of intercostal central 12 side disc, absent or rarely on Formation, Antwerpen Member, Panopea level),
portion, and on auricles of left valve. Radial and corn- specimens (RM Colin, Antwerp-Ploegstraat, same
marginal macro-ornament in early ontogeny. In later stratigraphic level), 16 specimens (RM Colin, Antwerp-
growth stages solid or more or less hollow primary and Kleine Ring motorway exit at Luitenant Lippenslaan, 47
33 Occurrence — Pseudamussium is same stratigraphic level), specimens (RM Colin, edegemense rare in the
Antwerp-underground Schijnpoort, same stratigraphic Edegem and Zonderschot members, but fairly common in
level), 11 specimens (RM Colin, Antwerp-Kleine Ring the Panopea bed (Antwerpen Member). According to
motorway, Berchem, same stratigraphic level), 26 Hooyberghs (1996a, b), these units of the Berchem
Berchem specimens (RM Colin, Heist-op-den-Berg, Formation are of Early Miocene (Aquitanian-Burdi-
Formation, Zonderschot 12 however Member), specimens (RM galian) age, according to Janssen (1998) they Colin, Antwerp-Kennedy Tunnel, Berchem Formation, should be included in the Middle Miocene Langhian
Edegem Member), 12 specimens (Antwerp-Kleine Ring (Hemmoorian, Behrendorfian in the North Sea basin).
Berchem [co-ordinates 154.5-155.7, 209.5-211.8], The sediment type of these members is a rather coarse,
well-sorted Formation, Antwerpen Member). glauconitic sand; they have yielded warm,
Dimensions — see Table 2. rather deep water faunas, at least partially preserved in
Description — Rather small, tear-shaped, inequivalve situ (e.g. Panopea level). So far, P. edegemense has not
shell, taller than wide, left valve more tumid than right. been found in the Deurne Member (Diest Formation,
Auricles both sides auricle on clearly different, posterior Late Miocene). Outside the Antwerp area, the species
third of anterior. found in the Middle Miocene only one the length Right valve with was of Haamstede (the
about twenty well-developed primary radial ribs, which Netherlands) (RGM collection, unpublished). P.
in young specimens are as wide as the intercostal spaces, edegemense is endemic for the Miocene North Sea basin.
in but adults become twice as wide; further from umbo,
ribs become obsolete. Ribs are hollow internally and at
first later 6-8 comprise 2, secondary ribs, roofed by a Pseudamussium princeps (J. de C. Sowerby, 1826)
thin layer of shell material, which may partially be lost in PI. 1, figs 1, 2; PI. 2, fig. 1
some specimens (e.g. holotype; see Glibert, 1945, fig.
* 1826 Pecten J. de 3c). At the anterior and posterior margins, only densely princeps C. Sowerby, p. 80, pi. 542,
2. striae at the fig- packed antimarginal occur; directly margins,
1851 Pecten Princeps — Wood, 31, pi. 6, fig. 1. these striae are perpendicular to the radial ribs, near the p.
1874 Pecten var. Princeps, pseudo-Princeps Wood, p. centre of the disc they take an umbonal direction. 103, pi. 8, fig. 9. Intercostal areas between primary ribs have mostly three
1878 Pecten princeps — Nyst, pi. 14, fig. 1 secondary ribs, crossed by commarginal riblets that do
1881 Pecten — 148. princeps Nyst, p. not continue on the primary ribs and form weak scales 1939 — Chlamys princeps Sowerby Roger, p. 170, pi. when crossing the secondary ribs. Growth lines rarely 24, figs 4, 5; pi. 25, fig. 5; pi. 27, fig. 3. visible. Anterior auricle shows central area with five 1955 Chlamys princeps (Sowerby) — Glibert & de
close-set tuberculate ribs, with lines 24. heavy, only growth Heinzelin, p.
above and most obvious auricle 1957 1826 — below, above; posterior Chlamys princeps Sowerby, sp. Glibert, p. shows antimarginal ornament, continuous with that of 25.
1969 de disc edges. Pallial line straight, ligament pit shallow, Chlamys (Chlamys) princeps (J. C. Sowerby,
— van Altena et 12, 1, chondrophore rather large but shallow. Ctenolium weak, 1826) Regteren al., p. fig. pi. 9, fig. 35. often virtually absent, with 6-8 denticles. Interior surface fairly glossy, with weak primary ribs visible; muscle impressions large, rounded. Locus typicus — Ramsholt, Suffolk (United Kingdom).
Stratum — Coralline Ornament of left valve shows the same elements as typicum Crag (Early Pliocene).
Material studied — IRScNB 1ST 1811 the right one, but with more tumid primary ribs and (material
illustrated Diest commarginal striae on a larger portion of the disc, as by Nyst, 1878; Deurne, Formation,
striae Deurne RGM 394 17 well as commarginal continuing over the primary Member), 096-097, specimens ribs. Secondary intercostal radial ornament lacking, only (RGM Colin, Kallo-Vrasenedok, Kattendijk Formation, Petaloconchus 5 scales present, stronger than those on right valve. level), specimens (RM Colin, same
Anterior auricle with 5-7 tuberculate radial ribs, slightly locality and stratigraphic level), 14 specimens (RM
Colin, Kallo-Verrebroekdok, same 5 narrower than intercostal areas. Tubercles appear where stratigraphic level), radial Colin, ribs and weaker commarginal lines cross. specimens (RM Antwerp-KJeine Ring motorway,
Discussion — The left valve of P. edegemense is Borgerhout, Diest Formation, Deurne Member), 12 described here for the first time. Hollow radial ribs were specimens (RM Colin, Kallo-Vrasenedok, Kattendijk held to be the most important character distinguishing the Formation, above Petaloconchus level), 3 specimens
mentioned Colin, water genusKarnekampia by Wagner (1988), who (RM purification plant), Antwerp-Schijn- this kind of The 4 ornament for the left valve only. present poort, Kattendijk Formation, Ditrupa level), specimens Kallo-'Vierde material shows it to occur on both valves. However, in (HD Colin, Havendok', Kattendijk view of the wide range of intraspecific varation in Formation). pectinids, we consider this to be an insufficient character Dimensions— see Table 2. for the erection — Shell thin, to c. 168 mm tall, of a separate genus. Description large, up 48
of lines and about 7 juveniles slightly taller than wide, adults wider than tall, number strong growth antimarginal
left valve than the central/umbonal These riblets slightly inequivalve, more convex right. riblets on portion. are
Shell inequilateral, auricles unequal, umbonal angle c. weaker and more closely spaced than those on posterior
half of auricle show 110°. Byssal notch moderately deep, byssal fasciole auricle. Highest quarter and lower
rather broad. Active ctenolium present in juveniles, prominent growth lines. Secondary ornament mostly
than left valve. line consisting of seven tuberous denticles, disappearing in present, but weaker on Hinge
adults. Resilifer triangular. Cardinal crura well straight.
developed. Discussion — Juvenile specimens have been collected
Ornament in left valve of early juveniles with from the Petaloconchus level, a portion of the Katten-
numerous, very fine subequal radial riblets, some of dijk Formation until now sampled extensively in situ at
is characterised dense colonies which become stronger gradually. Commarginal growth Kallo only. This level by
lines inconspicuous in this portion of shell. Older of the bivalve Petaloconchus glomeratus (Linne, 1758)
with twice the and has molluscan faunas, juveniles c. 22 primary radial costae, up to yielded highly interesting
width of the intercostal but Ribs which of the areas, mostly narrower. amongst numerous representatives
consist in central portion of disc of 4-6 secondary radial Emarginulidae and Polyplacophora are of particular note.
riblets; in the central intercostal areas, 4 secondary riblets The Petaloconchus colonies probably provided
to are developed. Near the anterior area, the distinction sufficiently hard substrates for those molluscs settle.
Juveniles of have between primary and secondary ornament disappears, P. princeps a well-developed
which that with 6 subequal ribs present. In the intercostal areas of ctenolium, suggests they were probably
the posterior third and anterior quarter of the disc, attached to the substrate by their byssus. The active
delicate antimarginal striae occur, forming angles of 45° ctenolium is lost in adults, and these were probably free
Petaloconchus in relation to radial ribs. Secondary radial ornament living; adult shells are absent from the
scattered in the where absent in these portions of shell. Posteriorly, these striae level, but do occur overlying beds,
Petaloconchus level sand is already start in early growth stages, being nearly as juveniles are absent. The
radial ribs. well contains of and in strong as Late juvenile ornament mostly sorted, large amounts glauconite,
from visible the number fossils commences a clearly growth line, gradually uppermost part yields a probably
of the developing in other specimens through strengthening of preserved in life position, e.g. crustacean burrows
in calm some radial ribs. In adult specimens, primary and Ophiomorpha type, which suggests deposition
from the secondary ornament equally strong, consisting of up to waters. However, P. princeps is also known
the disc Miocene ‘Heterocetus Sand' 80 radial ribs. Antimarginal ornament may cover Late (Diest Formation),
intersections of which is a coarse sand unit, with and blocks completely. Scales may be present on gravel large turbulent growth lines and radial ribs. Posterior auricle half the of sandstone, suggesting deposition in a setting.
difference length of anterior in juveniles, to three-quarters in adults, In P. princeps, there usually is a clear
subadult and adult with 3-4 strong, spiny antimarginal riblets. Anterior between the ornament of juvenile,
auricle with 5-6 primary antimarginal riblets bearing specimens; juveniles have far more numerous radial ribs
half of intercostal than which also In the scales, each occupying about area. subadults, are subequal. adults,
Secondary ornament in intercostal area on both anterior distinction between primary and secondary ribs
and posterior auricles consisting posteriorly of narrow disappears and the number of radials increases. In some
of subadult is in grooves, forming angles of c. 30° with primary riblets, specimens, the onset ornament gradual,
and directed to hinge line. Anteriorly, secondary others it is sudden. The development of spines on auricle
the of the remainder of ornament on auricle best developed near hinge line and ribs is highly variable, ornament
of of 4-5 furrows, shell however little variation, in there consisting groups narrow showing mainly strength
radiating from a common origin on the anterior portion of striae on juvenile portion of shell and in size of area
of auricle. covered in striae instead of secondary radial ornament.
Ornament of right valve largely corresponding to that Pseudamussium princeps differs markedly from P.
hollow radial and in the of left, but primary ribs on central portion of disc clearly edegemense in lacking ribs,
size of the auricles in of wider and flatter; in rare specimens only secondary relative posterior (i.e. excess
50% of of anterior auricles in the and riblets are present. Scales on radial ribs invariably length former,
restricted third in the latter Pseudamussium absent. Antimarginal striae weaker, often to barely a species).
anterior also much size than P. posterior portion of shell. Ribs on portion princeps grows to a larger
becoming gradually more equal by thickening of edegemense.
considered secondary ornament; ribs then as wide as intercostal Wood (1851) Pecten sublaevigatus Nyst,
be of Pseudamussium areas. Posterior auricle half the length of anterior, with 4 1843 to a synonym princeps.
is much smaller than P. prominent, narrow antimarginal riblets, which become However, Nyst's species
has different adult and weaker near the posterior margin; may be ornamented princeps, an utterly ornament,
weaker occurs in the Wemmel Member at Laeken, with up to 6 well-developed or spines. Secondary (Late Eocene)
ornament lacking. Anterior auricle with a variable near Brussels. 49
Pseudamussium lilli (Pusch, 1837) Miocenestrata) has up to 35 radial ribs, mostly occurring
of intercostal of the PI. 2, fig. 2 in groups two, and with areas same
width of radial ribs. as a couple Secondary ornament may
* 5. 1837 Pecten lilli Pusch, p. 40, pi. 5, fig. be present, but in some specimens there are
Pecten 1843 Lamalii Nyst, p. 305, pi. 22, fig. 5b, d; pi. commarginal, scale-like striae instead of radial inter-
24, fig. 5. of costal ribs. In both types, primary ribs consist mostly 1869 Pecten scissus 9. Favre, p. 151,pi. 13, fig. with in up to ten secondary ribs, very narrow spaces
1936 Chlamys (Flexopecten) scissa Favre — Friedberg, between. Rarely, weak spines are present on ribs. Left p. 236, pi. 39, figs 16-20; pi. 40, figs 1, 2. valve with similar ornament, but number of primary ribs
1936 — Chlamys (Flexopecten) Lilli Pusch Friedberg, p. mostly higher (18-20), while more valves show type 2 241, pi. 40, figs 7-13. ornament, and ribs rarely bifurcate. Radial as well as
1939 scissa Favre — Chlamys Roger, p. 187,pi. 19, figs ornament occur in intercostal areas. 7-16. commarginal may
Anterior auricle of valve about twice the of 1939 Pusch — right length Chlamys lilli Roger, p. 187, pi. 19, figs
17-20. posterior, with 4 heavy, scaled ribs near upper margin,
1945 1837 — Pecten (Pallium) lilli Pusch, Glibert, p. 73, area bordering disc with growth lines and weak
1. pi. 5, fig. antimarginal ornament. Posterior auricle with 5 faintly
1964 Muller, — Chlamys (Pallium) tigerina (O.F. 1776) delimited, scaled primary ribs over entire height.
142 Anderson p. (non Muller) Between these, wide secondary ribs occur with very
1984 Pseudamussium lilli (Pusch, 1837) — Janssen, p. narrow intercostal areas, occasionally co-occurring with 54, pi. 25, figs 1-5. antimarginal striae. In left valve, a similar but mostly 1986 Chlamys (Flexopecten) scissus (Favre, 1869) — weaker auricle ornament is present. Studencka, p. 40, pi. 4, figs 8, 9; pi. 5, figs 1-10; pi. Discussion — For more complete synonymy lists and 6, figs 1,2, 5, 6, 9,10. illustrations of the present species' range of variation, 1998 Flexopecten lilli (Pusch, 1837) — Studencka et al., reference is made to Glibert and Studencka p. 314. (1945) Studencka — sub C. 1998 Flexopecten scissus (Favre, 1869) Studencka el (1986, (F.) scissus). Roger (1939),
314. and Studencka al. considered P. lilli al., p. (1986) et (1998)
and P. scissus to be distinct species, with a lower number
Locus typicus — Wieliczka, Poland. of radial ribs in the latter (see Roger, 1939), and the
Stratum — Badenian(Miocene). radial typicum presence in the latter of tubercles where and
Material studied — IRScNB 1ST 1756 (Houthalen, commarginal ornament intersect (see Studencka et al.,
Belgian province of Limburg, Berchem Formation, 1998). Similar tubercles have been observed in material
Houthalen IRScNB 1ST 1935, 1942, 3816 Member), from the Miocene of Belgium, but only very rarely. In P. Berchem Formation, (Antwerp, Antwerpen Member), lilli, however, the ornament is extremely variable; we IRScNB 1ST 1939-1940 Berchem Formation, (Edegem, consider a single character to be too small a basis for
1 Colin, Kallo- Edegem Member), specimen (RM specific distinction. In addition, in the papers cited both
Petaloconchus Vrasenedok, Kattendijk Formation, 'species' are recorded from largely the same distribution
140 level), specimens (RM Colin, Antwerp-underground area, viz. North Sea Basin, Poland and the Paratethys, Berchem Schoolplein, Formation, Antwerpen Member, including the Middle East, but without records from the
level. Glycymeris Mediterranean and Atlantic. This distribution pattern is
Dimensions— Table 2. see of note, since it suggests faunal exchange between the
Description — Rather small, slightly inequivalve, flat North Sea Basin and the Paratethys during the Miocene. shell with near-circular disc and rather small The others Janssen & unequal, same was proposed amongst by auricles. No ctenolium. Ligament pit small, triangular, Zorn (1993).
wider than tall. Muscle insertion rounded. both shallow, Right Glibert (1945) also distinguished types of valve usually slightly more tumid than left. Ornament ornament described here, with type 1 referred to as
first either of radial 'forma and 2 'formae lilli-kneri’. The extraordinarily variable, at consisting scissus’, type as ribs divided into and of primary secondary ones, or equal present species is here considered to be assignable to
ornament but of the strength; secondly, commarginal develops, Pseudamussium on account presence of anti- this is much weaker. In both ribs be valves, primary may marginal ornament on the posterior auricle. However, hollow and composed of several secondary ones. this ornament is less well developed than in its congeners
Antimarginal ornament absent on disc. In general, two discussed here.
types of ornament may be distinguished: on right valves Occurrence — Pseudamussium lilli is known to date in of type 1 (commonest in material from the Miocene of the North Sea basin from Belgium (Edegem, Antwerpen the is lower than left Belgium), number of radial ribs on and Zonderschot Members), from the Netherlands
with the valves, right valves having about ten primary (Aalten Member, Miste Bed, see Janssen, 1984; Aalten
often Intercostal less wide and ribs, bifurcating. areas are Member, Stemerdink Bed, see Janse & Janssen, 1983) mostly show secondary radial ornament. Type 2 (rarer in and from Germany (Reinbek Schichten, Twistringen 50
Bislicher weak. Schichten, Schichten, see Anderson, 1964). A are mostly present. Growth lines Near umbo,
single specimen, collected from Pliocene strata at Kallo, tubercles often are present on and between ribs, effacing
subsequently was broken during transport. on younger portions of shell. Weak anti-marginal
ornament on anterior and posterior margins. Anterior
auricle with 5-7 radial ribs, lacking on ventral portion.
Ribs and covered with Pseudamussium sulcatum (Müller, 1776) wider than intercostal areas strong
PI. 3 tubercles. Growth lines line in 8 2, fig. strong, ending on hinge
spines, perpendicular to radial ribs. Posterior auricle with
* 1776 Pecten 248. sulcatus Midler, p. 5-7 tuberculate radial ribs, much weaker than those on
Pecten Bruei 1826 Payraudeau, p. 78, pi. 2, figs 10-14. anterior auricle. Antimarginal ornament often is well
1851 Pecten Bruei, — 5, Payraudeau Wood, p. 29, pi. developed. 3. fig. Ornament of left valve similar, often with stronger
1939 — Chlamys bruei Payraudeau Roger, p. 201, pi. commarginal intercostal ornament and heavier rib 21, figs 3-9. tubercles; antimarginal ornament also often more 1965 Pseudamussium (Zygochlamys) bruei (Payraudeau, pronounced. Primary ribs often hollow, composed of
— Glibert de 36. 1826) & van Poel, p. is several secondary ones, but this not always the case.
1976 — Chlamys (Chlamys) sulcata (Midler) Tebble, p.
Discussion — The species is related to P. 59, pi. 6, fig. F. present closely lilli (see above), which is also known from the 1988 Karnekampia bruei (Payraudeau, 1826) —
1. Petaloconchus level at Kallo. Wagner, p. 42, fig. (Kattendijk Formation)
1988 sulcata — Both taxa have shell and variable ornament Karnekampia (Midler, 1776) Wagner, p. shape widely
2. 42, fig. in common, often with scales in intercostal areas;
1991 Chlamys (Chlamys) bruei (Payraudeau, 1826) — in tubercles can occur younger growth stages, which Rombouts, 9, 23, fig. 5. p. pi. holds especially true for 'forma scissus’ of P. lilli.
1993 Chlamys bruei (Payraudeau, 1826) — Poppe & However, in P. lilli there is a tendency for radial ribs to 4. Goto, p. 60, pi. 7, fig. form larger clusters; moreover, ribs are hollow in left and
1995 Karnekampia aff. bruei (Payraudeau, 1826) — right valves. Pseudamussium lilli and P. sulcatum could Vera-Pelaez 100. et al., p. well form an evolutionary lineage.
Wood (1851) described and illustrated as Pecten Locus typicus — Denmark. Bruei a specimen from the Coralline Crag (Early Stratum typicum — Recent. Pliocene) of Sutton (East Anglia, United Kingdom). Material studied — One specimen (RM Colin, off There are no records from the Pliocene of the Morano Island, - 200 m, near Venice, Recent), 5 Netherlands. Vera-Pelaez et al. (1995) recorded P. specimens (HD Colin, off Trondheim, Norway, - 120- sulcatum from the Early Pliocene (Zanclean) of Malaga 140 m, Recent), 3 specimens (HD Colin, off South (Spain), while Glibert & van de Poel (1965) mentioned Island, - 460-520 m, Recent), 3 specimens (HD Colin, Pliocene (Astian) material from Millas, Roussillon off Koster Island, western Sweden, - 73-110 m, Recent), (France). Roger (1939) reported its occurrence in the 5 specimens (HD Colin, off Capraia Island, Italy, - 120- Italian Pliocene, and considered Chlamys (Flexopecten) 140 m, Recent), 4 specimens (RM Colin, Kallo- ampferi Kautsky, 1928 (p. 262, pi. 7, fig. 8) from the Verrebroekdok, Kattendijk Formation, Petalo-conchus Badenian(Middle Miocene) of Steinabrunn (Austria) to level). be a junior synonym of P. sulcatum. However, more Dimensions — see Table 2. material is needed to decide whether this form should be
Description — Rather small species, fossil specimens assigned to P. sulcatum, or rather to P. lilli. studied up to 20 mm in height, extant ones up to 30 mm. Tebble (1976), Rombouts (1991) and Poppe & Goto Shell thin and brittle. Disc very flat, near-circular to (1993) recorded extant P. sulcatum from Iceland and slightly taller than wide, inequivalve with left valve Norway to the Cape Verde Islands and from the Medi- slightly more convex than right. Anterior auricle about terranean, in circalittoral settings, and down to depths of three times the length of the posterior, with a prominent sand 2,500 m, on and mud, being rare everywhere. byssal notch. Active ctenolium with about8 denticles.
Right valve with 20-40 weak primary ribs, widely
separated or more closely spaced, depending on rib Pseudamussium clavatum (Poli, 1795) number. Ribs often form clusters, mostly consisting of PI. 2, figs 4-6 two ribs, occasionally more. In and on primary ribs,
secondary ones occur on the central portion of disc, 2-8 1795 Ostrea inflexa Poli, p. 160, pi. 28, fig. 5. in between ribs, 0-4 on them. Secondary ribs often not * 1795 Ostrea clavata Poli, 17. p. 161, pi. 28, fig. much weaker than primary ones, especially near anterior
1851 Pecten Danicus Chemnitz — Wood, p. 30, pi. 4, and posterior margins. In intercostal areas between fig. 2. primary ribs, low commarginal scales often occur. On 1939 clavata Poli — Chlamys Roger, p. 208, pi. 28, figs scales primary ribs, especially anteriorly, higher spiny 4, 5, 9-12,14. 51
1950 Pecten (Pseudamussium) septemradiatum (Miiller, becoming weaker ventrally. Posterior auricle with 3-5
1776)— Heering, p. 49, pi. 14, fig. 10. faintly delimited ribs, clearly showing antimarginal
1956 Chlamys (Peplum) clavata (Poli) — Rasmussen, p. ornament. Interior of valve glossy, showing primary ribs 32, pi. 1, fig. 5. and in some specimens the largest secondary ones on
1957 1795 — Chlamys (Peplum) clavatum Poli, sp. ventral margin. 11. Glibert, p. 28, pl. 1, fig. Left valve flat, with 3 primary ribs and relatively
1968 clavata — 32. Chlamys (Poli 1795) Rasmussen, p. much wider intercostal areas (1-2 times the width of 1969 Pseudamussium (Pseudamussium) clavatum (Poli, primary ribs). Secondary radial ornament present. Ten — Altena 1795) van Regteren et al., p. 17, pi. 11, ribs radials, 5 fig. 40; text-fig. 2a, b. closely spaced on primary more widely
ones in between, both small scales. 1991 Pseudamussium (Peplum) clavatum (Poli, 1795) — spaced showing
10. ornament anterior and Rombouts, p. 57, pi. 20, fig. Antimarginal on posterior
1993 Pseudamussium clavatum (Poli, 1795)— Poppe & margins. Ornament on auricles similar to that in right
Goto, 70, 10, 6. ribs finer p. pi. fig. valves, but clearer, and more widely separated.
Discussion — The is known date in present species to
Locus — typicus Sicily (Italy). the North Sea Basin from the Late Miocene to the Early
Stratum — Recent. typicum Pliocene, and from the Early Pliocene onwards in the
Material studied — IRScNB 1ST 4801 Diest (Deurne, Mediterranean, extending from Algeria to Syria (Roger, Formation, Deurne Member), IRScNB 1ST 4802 1939). In Belgium, P. clavatum is known from the Diest
(Berchem, same stratigraphic level), as well as 20 Formation, occurring both in fine sands of the Deurne specimens (RM Colin, Borgerhout-KJeine Ring Member as well as in the overlying gravels of the
' Diest Heterocetus 4 motorway, Formation, sand'), ‘Heterocetus Sand'. In the Kattendijk Formation, it is
Colin, same Diest in the in the specimens (RM locality, Formation, common lower part, especially Similipecten Deurne Member), 5 specimens (RM Colin, Deurne, bed and in the level with Ophiomorpha-type crustacean strati- water purification plant at Schijnpoort, same burrows immediately above the Petaloconchus level. It is graphic level), 5 specimens (RM Colin, Deurne- absent from the upper Ditrupa- -Glycymeris beds
Rivierenhof pond, same stratigraphic level), 1 specimen (Kattendijk Formation), as well as from younger Colin, old Gram, (RM clay pit Denmark, 'Gram Stufe'), Pliocene strata. In the Netherlands, material has been
3 Ohle Gross specimens (RM Colin, sandpit, Pampau, recorded from beaches and boreholes; in the United
Holstein 1 (Germany), 'Langenfeld Stufe'), specimen Kingdom, the species is rare in the Coralline Crag. (RM basal Colin, Kallo-tunnel, Kattendijk Formation, Poppe & Goto (1993) recorded it from the British gravel), 6 specimen Kallo-tunnel, Katten- and (RM Colin, Isles to Portugal from the Mediterranean, on muddy dijk Formation, below Petaloconchus level), 44 bottoms in depths between 5 and 1,400 m. specimens (RM Colin, Kallo-Vrasenedok, Kattendijk
Formation), 67 specimens (RM Colin, same locality,
Kattendijk Formation, Similipecten level), 2 specimens ACKNOWLEDGEMENTS (RM Colin, Antwerp-underground Schijnpoort, Katten- dijk Formation). We wish to thank A.V. Dhondt, A.W. Janssen and F.P.
Dimensions— see Table 2. Wesselingh for permission to study material contained in
- Medium-sized Description (up to 30 mm in height), the IRScNB and RGM collections, and M. Wagenaar and tear-shaped disc, strongly inequivalve, right valve tumid, W. Miseur (IRScNB) for assistance in preparation of left valve flat, with a depression below umbo. Auricles photographs. third small, unequal, posterior measuring but a of length of anterior; byssal notch absent. Active ctenolium weak or absent.
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preserved at various times and depths in the earth, 6. September 1999. 54
Character Pseudomussium Morch, 1853 Palliolum Monterosato, 1884
Type species: Pecten septemradiatus Type species: Pecten incomparabilis
Muller, 1776 by SD: ICNZ Op. 714 Risso, 1826 by SD: Crosse, 1885
Size to 180 mm Up high Up to 30 mm high
Convexity RV more convex than LV RV slightly more convexthan LV
Shape Rarely equivalve, mostly inequivalve; Equivalve, rarely inequivalve;
equilateral, seldom inequilateral equilateral
Rarely smooth, mostly radially undulated Smooth
Orbicular to slightly elongate(oblong) Orbicular
Microsculpture Antimarginal on flanks of disc Antimarginal
Macrosculpture Primary radial lyrae, secondary radial Absent on disc, present on auricles
riblets and secondary commarginal
striae in early ontogeny Auricles .Anterior larger than posterior Anterior much larger than posterior Byssus Byssal notch moderately shallow, mostly Notch deep; byssal fasciole broad,
deep; byssal fasciole narrow or absent, active or inactive ctenolium present,
ctenolium active present in juveniles, absent well developed
in adults to inactive and nearly absent
Table 1. Differences between the Pseudamussium and Palliolum. Bold: characters. genera most important
Specimen Height (mm) Length (mm) Diameter (mm) Posterior auricle
lengthlength (mm)
P. princeps, right valve juvenile 31.2 27.5 3.3 6.2
P. princeps, left valve juvenile 24.424.4 21.0 3.4 6*
P. princeps, adult bivalved 137.2 142.7142.7 39.8 39.639.6
P. edegemensis, left valvevalve 26.3 24.6 4.7 3.2
P. edegemensis, right valve 26.8 23.1 3.0 3.3
P. lilli, right valve 16.216.2 16.316.3 2.4 2.3
P. sulcatum,sulcatum, left valve 18.118.1 19.4 2.7 3.2
P. 26.026.0 23.3 8.3 4.24.2 clavatum, bivalved spec. 23.3
* P. clavatum, right valve 28.828.8 25.4 5.2
** P. clavatum, right valve 31.8 29.3 7.0
* Table 2. Measurements of illustrated in Pls auricle size material 1, 2; = damaged, approximate.
PLATE 1
Figs 1,2. Pseudamussium princeps (J. de C. Sowerby, 1826), juvenile left and right valves, respectively; Kallo-Vrasenedok
(Beveren, Oost-Vlaanderen, Belgium), Early Pliocene (Kattendijk Formation, Petaloconchus level), RGM 394 096-097, x
3.4 (1a, 2) and x 6 (1b).
4. Pseudamussium and left Figs 3, edegemense (Glibert, 1945), right valve, respectively; temporary outcrop garage Gaumont Cinema
(Antwerp, Belgium), Early Miocene (Berchem Formation, Antwerpen Member, Panopea level), IRScNB IST 6384 and
IST 6394, respectively, x 3.4 and x 3.3, respectively. 55\1
PLATE 1 56
PLATE 2
Fig. 1. Pseudamussium lilli (Pusch, 1837), right valve; Kallo-Vrasenedok (Beveren, Oost-Vlaanderen, Belgium), Early Pliocene
(Kattendijk Formation, Petaloconchus level), Marquet Colln, x 2.4 (a) and x 3.4 (b).
Fig. 2. Pseudamussium sulcatum (Müller, 1776), left valve; Kallo-Verrebroekdok (Beveren, Oost-Vlaanderen, Belgium), Early
Pliocene (Kattendijk Formation, Petaloconchus level), x 2.9 (a) and x 4.6 (b).
Fig. 3. Pseudamussium princeps (J. de C. Sowerby, 1826), adult; Kallo-Vrasenedok (Beveren, Oost-Vlaanderen, Belgium), Early
Pliocene (Kattendijk Formation, Petaloconchus level), Marquet Colln; left valve, x 0.34 (a); right valve, x 0.34 (b); both
valves, x 0.45 (c).
Figs 4, 5. Pseudamussium clavatum (Poli, 1795), right valve and articulated specimen, respectively; Kallo-Vrasenedok (Beveren,
Pliocene Oost-Vlaanderen, Belgium), Early (Kattendijk Formation, Similipecten level, Marquet Colln, x 1.8 (4); left valve,
x 2 (5a), right valve, x 2 (5b). 57\2
PLATE 2