Krausella minuta, a nomen nudum in ostracodology, and three new species of Cardobairdia Bold, 1960 from the Campanian of Belgium and the Cenomanian of southern England

Van Veen (1936b) found the ostracod species Krausella minuta Triebel, in deposits of the uppermost Maastrichtian from the Valley of the Jeker, South Limburg, The Netherlands. Investigation has shown that Triebel never published any data on this species, so the name Krausella minuta has to be rejected, being a nomen nudum. In the boreholes of Kallo (27 E 148) and Knokke (11 E 138), in the northwestern part of Belgium, a related, yet undescribed species occurs, for which the name Cardobairdia triebeli sp. nov. is proposed. This taxon was found in deposits of mainly Lower Campanian age. Another new species, Cardobairdia rectimarginata, is described from the Campanian in the Knokke Borehole. The specimens of Cardobairdia minuta from the Cenomanian from southern England belong to a new species, defined here as C. cenomanensis.


INTRODUCTION
During the last 50 years, many authors have mentioned the presence of the ostracod species Krausella minuta, in deposits of Cretaceous as well as of Ordovician age. The first, but incomplete description of this taxon was by Van Veen (1 936b), who attributed the species to Triebel : the latter had sent Van Veen some photographs of an ostracod from the Lower Cretaceous of Germany, labelled "(?) Krausella rninuta ". Van Veen (ihid. ) declares to have found the same taxon in deposits of the uppermost Cretaceous of South Limburg, The Netherlands, namely in the "dritten Bryozoenschicht von Staring im Jekertal" (see fig. I), which is part of the Nekum Member, Maastricht Formation (see fig. 2). The same author mentions a slight difference with Triebel's material, namely a smaller carapace, but explains this as due to sexual dimorphism. Contrary to Triebel's opinion, Van Veen did not doubt the attribution of the species minuta to the genus Krausella Ulrich, 1894. Study of the existing literature on Upper Cretaceous ostracods has not revealed any publication, in which Triebel has described or mentioned Krausella minuta as a new species. This was confirmed by Malz (Frankfurt am Main, F.R.G.) in a letter to the present author, in which he states that Triebel never published anything on Krausella minuta, therefore this taxon is anomen nudum. Moreover, the collections of Triebel, stored at the Senckenberg Institute, do not include any individuals of this species.
The Van Veen collection only comprises one slide, number 0.1418, labelled as "Krausella minura Triebel Jekerdal of Uhlenbroek (1912). This material differs from Cardohairdia trieheli sp. nov. by the greatest width being distinctly behind mid-length, the right valve is higher anteriorly, with a convex ventral margin, while the posterior end is rather blunt. Because of a lack of such specimenstwo individuals in the collection Van Veen, and one valve from the borehole at Hoeselt, NE-Belgiumwe can not give a fuller detaileddescription, and so not allowing the erection of anew species. The Cenomanian deposits of southern England comprise a relatedcardohairdia species, which was described by Weaver (1982) as C. minuta. Because of considerable differences with the Belgian and Dutch specimens, we define here a new species : C. cenomanensis.
Harris (1 957) described a new species, Rayella minuta, from the Simpson Group, Lower Ordovicium in Oklahoma (U.S.A.). According to Copeland (1974), who also studied Ostracoda from the Mohawkian of Oklahoma, this taxon would belong to the genus Krausella. Copeland (ihid.) does not refer to the publication of Van Veen, probably because he wasnot aware of the synonymy. However, his description and his figures do not match Kr. minuta sensu Van Veen. Therefore, and because of the considerable difference in age of the deposits under study, the material of neither Harris, nor Copeland, can belong to Van Veen's species.

SPECIMEN REPOSITORIES
All specimens of C. rectimarginata and C . trieheli are deposited in the collections of the "Laboratorium voor Paleontologie" of the State University in Ghent. The material of C. cenomanensis , collected by Dr. Weaver (Wormley), is housed in the British Museum (Natural History), Department of Palaeontology, London. Derivation of name. After the age of the deposits in which the species is found : Cenomanian. Diagnosis. A species belonging to the genus Curdohair-dia characterised by : the left valves have rounded anterior margins and rather blunted posterior margins; right valves are merely triangular with swollen sides, with a distinct bending point posterodorsally; ventral side convex; greatest height in front of mid-length.
Material. 479 valves and carapaces from southern England (Weaver collection). Locality and horizon. Bluebell Hill, Chatham, Kent, sample BB 12, Grey Chalk, Upper Cenomanian. Description. The left valves are suboval in lateral view, with a symmetrically rounded anterior extremity. The posterior end is rather blunt, composed of an almost vertical part, forming a clear angle with the ventral side. The dorsal margin is convex, ending at a distinct bending point posteriorly. The ventral side is regular convex. Greatest height is measured somewhat in front of mid-length. The right valves are lower and subtriangular in shape, with swollen sides. The posterior extremity has a low bending point. The longitudinal borders are convex. Greatest height lies in front of the mid-point. Left valve overlaps the right one along the entire margin, except at the posterior, where the right valve extends. Lateral surface is smooth. The greatest width is measured near the middle of the carapaces. Sexual dimorphism is pronounced : males are more elongate and less high than females and the posterior is more drawn-out. Hinge of the right valve consists of a low, elongate, crenulate tooth anteriorly, followed by a smooth median groove and a crenulate posterior tooth, continuing as a ridge around the posterior end of the valve. The marginal zone is rather narrow, without vestibules. Other internal details not seen.  (Herrig, 1966); The Netherlands : Drente, Middle Turonian to Lower Santonian ("Mergel"and "Schreibkreide") (Bonnema, 1940).  Weaver (1982) as Cardohoirdiu minufa (van Veen, 1936) differs in having left valves with a distinct curve at the dorsal margin, a lower posterior end, while the right female valves are obviously narrower. These specimens are described in this paper as C. cenomutwnsis sp. nov. See also "Introduction". Occurrence. Kallo : sample KA-560, probably Gulpen Formation, Upper Campanian. Knokke : Gulpen Formation, Lower Campanian to uppermost Campanian. Stratigraphical and geographical range. Denmark : Maastrichtian (Joergensen, 1979); Federal Republic of Germany: Liigerdorf & Kronsmoor, Campanian (pilula zone to fangei zone) (Personal collection) ; German Democratic Republic : Riigen, Baltic Sea, Lower Maastrichtian ("Weissen Schreibkreide") (Herrig, 1966) ; Great Britain : Isle of Wight, ? Coniacian to Campanian (Hart et a1 ., 1987) ; The Netherlands : Drente, Middle Turonian to Lower Santonian ("Mergel" and "Schreibkreide") (Bonnema, 1940).