Cainozoic Research, 7(1-2), pp. 69-72, April 2010

Globivenus barti n. sp. (, )

from the Neogene of The Netherlands

² Peter+W. Moerdijk¹ & George+F. Simons

'Kingstraat 14, 4336LG Middelburg, The Netherlands. E-mail: [email protected] 2 Beneluxlaan 23, 4334 GH Middelburg, The Netherlands.

Received 1 May 2009; revised version accepted 23 July 2009

Globivenus barti is described from material of the Westerschelde The Its strati- n. sp. dredged estuary (prov. Zeeland, Netherlands).

has been recorded in boreholes but the it graphic provenance not yet or outcrops, given preservation state presumably derives from

Early Pliocene deposits.

KEY WORDS:: Globivenus, Neogene, Westerschelde, North Sea Basin, new

Introduction Other material studied - RGM 566382c, 3/2 from type

locality, leg. A.C. Janse; n.n., 2/2 from Westerschelde near

of book the fossil shells of the As part working on a on Baarland, coll. H.A.A. de Jong; 1/2 from same locality,

Dutch beaches and estuaries, foreseen in 2010, venerid coll. G.F. Simons; 5/2 from same locality, coll. A.C. Rij-

bivalves studied. fossil venerid shells 5/2 from coll. 1/2 were Some dredged ken; same locality, A.P. Goetheer; n.n.,

from the Westerschelde (The Netherlands) could not be Westerschelde, material from “Rug van Baarland”, 1/2,

attributed to any of the known fossil or recent species of coll. A.P. Goetheer.

Veneridae. The shells are attributed here to a new species,

Globivenus barti - n. sp. Diagnosis A Globivenus with a protruding umbo and

moderately impressed lunule.

Systematic Palaeontology Description - The shell is very convex when viewed from

the side; a pair would make a heart-shaped outline. The Veneroidea 1815 Superfamily Rafinesque, shell is about as long as high. The lunule is impressed, Veneridae 1815 Family Rafinesque, partly concave but convex near the beaks (outline s-

Subfamily Venerinae Rafinesque, 1815 circumscribed shaped), by a narrow groove. The poorly Genus Globivenus Coen, 1934 (type-species effossa delimitedescutcheon can be observed in the right valve,

Philippi, 1836, Recent, Mediterranean) but is hard to determinefor the left valve because all ofthe

studied right valves are too much decorticated and/or worn.

The large protruding umbo is prosogyrate. The antero-

Globivenus barti n. sp. dorsal margin is convex, the anterior margin is narrowly

1-3 Figures rounded. The ventral and posterior margins are evenly

the outline of half circle rounded, describing nearly a (c.

material - RGM 566382a valve, The is from the Type (holotype): right 170°). posterior margin separated postero-

in Westerschelde near dredged Ellewoutsdijk (Zeeland, dorsal margin by a rounded edge. The delimitationof the

The Netherlands), leg. A.C. Janse (Fig. 1); RGM 566382b, ventraland posterior margins is subrounded. The sculpture

left A.C. Janse (paratype) valve, same locality, leg. (Fig. ofall studied valves is eroded to a considerableextent, but

valve, in 3); RGM 566381 (paratype), right dredged as far as it can be observed it consists of robust irregular

Westerschelde near Baarland (Zeeland, The Netherlands), commarginal ripples covered with microscopically fine

leg. P.W. Moerdijk (Fig. 2). commarginal threads. - 70-

1-3. Globivenus bar 1 All Westerschelde and Figures barti n. sp. Scale cm. dredgedfrom the presumably of an Early Pliocene age. (1)

RGM 566382a (holotype), RV, Westerschelde near Ellewoutsdijk (Prov. Zeeland,The Netherlands), leg. A.C. Janse: (a) external

internal frontal detailoffrontal view. view, (b) view, (c) view, (d) (2) RGM 566381 (paratype), RV, Westerschelde near Baarland

(Zeeland, The Netherlands), leg. P.W. Moerdijk: (a) external view, (b) internal view. (3) RGM 566382b (paratype), from type lo-

cality, leg. A.C. Janse: (a) internal view, (b) external view, (c) frontal view.

The commarginal sculpture is overlain by a pattern offaint developed. The left valve (LV) also contains three cardinal radial riblets of variable dimensions (Fig. Id). Where the teeth, the middle of which contains a radial groove. The

outer layer is eroded, the surface of the shell is covered anterior lateral tooth on the LV has a reduced knob-like with a fine regular radial sculpture. The base of the hinge outline. Adductor scars are about equal in size. The pallial plate is markedly curved upward behind the cardinal part sinus is triangular and short. The interior of the ventral of the hinge. The right valve (RV) hinge contains three margin is finely crenulated.

cardinal teeth of which the anterior lateral tooth is poorly - 71 -

Dimensions -All dimensions are in mm. RGM 566382a: cies all fit the genus Globivenus.

H W SD RGM 566382b: H In the the Westerschelde the Pliocene 27; 27; (semidiameter) 10; 34; deeper parts Late

W 35.5; SD 14; RGM 566381: H 25; B 25; SD 12. OosterhoutFormation and the BredaFormation, consisting

of Miocene as well as Early Pliocene sediments, are ex-

Derivatio nominis - Named after mr. H.A.A. (Bart) de posed. Shell fishing in the Westerschelde supplies tertiary

Jong (Middelburg, The Netherlands), a collectorof fossil fossil shells of mainly Pliocene age. Middle Miocene and

shells who showed us the shell that convinced us that this older shells occur as well, but they are very scarce. Fossils

is not identical with species Venus casina pseudoturgida of a Late Mioceneage are not rare, but less abundantthan

(d'Orbigny, 1852). Pliocene shells. However, all alleged Late Miocenespecies

calcitic are (e.g., pectinid and gryphaeid species). That

- fauna lacks the Type locality and stratum typicum The holotype derives aragonitic species, such as studied venerids.

This decalcificiation is feature in Miocene from the Westerschelde near Ellewoutsdijk (prov. Zeeland, common Late

faunas found in in the The Netherlands), coordinates approximately 51°22’ N, outcrops Antwerp area (Belgium).

The Westerschelde shells studied with- 3°50’ E. Since the material is suckerdredged, its strati- (18 specimens) are

out bleached, decorticated and worn. This graphic provenance is uncertain. Based on the preservation exception type

of of the shells is characteristic for fossil (see Discussion below) an Early Pliocene age is most preservation

Westerschelde shells of Pliocene such likely, although a Late Miocene age cannot be ruled out. an Early age, as

Glycymeris obovata ringelei Moerdijk & Van Nieulande,

2000, Astarte omalii omalii (De La Jonkaire, 1823) and Differentiation - Several authors have included Pliocene Venus casinapseudoturgida. Stratigraphic shells venerids from theNorth Sea Basin in their work (Sowerby, younger

from the Westerschelde are generally much better 1812-1846;Nyst, 1845,1881; Wood, 1856; Heering, 1950; pre- served. A Mioceneorigin cannot be excluded, but the most Glibert, 1945,1958, Janssen etal., 1984). They all mention likely stratigraphic of G. barti in of the some venerid species resembling venerids found in the age consequence

state of preservation is Early Pliocene. Dutch Westerschelde. These are Clausinella imbricata

(Sowerby, 1826) forma gibberosa (Wood, 1853), Venus

(Dosina) casina pseudoturgida (d'Orbigny, 1852) and Acknowledgements Venus (Ventricoloidea) multilamella (Lamarck, 1818).

Globivenusbarti differs from all these species by the im- We thank A.P. Goetheer (Ovezande), H.A.A. de pressed, partly concave lunule and by the ornament. At Jong

(Middelburg), F.A.D. van Nieulande and A.C. Rijken least in the anterior part of the shell commarginal ripples (Middelburg) for making theirmaterialavailable for study. instead of clear commarginal lamellae or ribs are present, We are thankful to A.C. Janse (Brielle) for providing two as well as a faintbut unmistakableradialpattern. The hinge ofthe type-specimens. Dr. F. Wesselingh (Naturalis, Lei- of G. barti is quite similar to that of V. casina forma den) is thanked for improvements ofearlier drafts of this pseudoturgida, but it is less robust and the nymph is com- for literature and for the excellent paratively shorter. The anterior lateral tooth of the left paper, photographs.

valve is better developed in G. barti than in Clausinella

imbricata, whereas it is shorter than in V. multilamella.

References In extreme forms of Clausinella imbricata forma gib-

berosa and Venus casinapseudoturgida the lunulecan also Coan, E.V., Valentich Scott, P. & Bernard, F.R. 2000. Bivalve be somewhat concave, but never to such a degree as in the seashells of Western North America. Marine Bivalve Mol- new species described here. lusks from Arctic Canada to Baja California.Santa Barbara Similarities with the extant Mediterranean and Eastern Museum ofNatural History. Monograph no. 2. Studies of Atlantic Globivenus effossa (Philippi, 1836) also exist. biodiversity no. 2. However, the lunula of the latter species is much deeper, Gilbert, M. 1945. Faune Malacologique du Miocene de la Bel-

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