Mesoleberis hollandica, Kornicker, Louis S., Van, Barry W. M., Bakel, Fraaije, René H. B. & Jagt, John W. M., 2006

Kornicker, Louis S., Van, Barry W. M., Bakel, Fraaije, René H. B. & Jagt, John W. M., 2006, Revision of Mesozoic Myodocopina (Ostracoda) and a new genus and species, Mesoleberis hollandica, from the Upper Cretaceous of Belgium and The Netherlands, Zootaxa 1246, pp. 15-54 : 23-27

Mesoleberis hollandica new species

( Figs. 1 , 2 , Table 2)

Etymology

Named after location of specimens.

Paratypes

MAB k. 2412, specimen deposited in the National Museum of Natural History as USNM 1083966. MAB k. 2422, specimen deposited in Natuurhistorisch Museum Maastricht as NHMM 2005 0 31. MAB k 2408­2411, 2413 ­2421, individual specimens deposited in Oertijdmuseum De Groene Poort (Boxtel, The Netherlands).

Stratum typicum

Levels IVf­4 and 5, Meerssen Member (Maastricht Formation), uppermost Maastrichtian (Belemnella (Neobelemnella) kazimiroviensis Zone).

Description of Carapace

Carapace oval in lateral view with short rostrum (rostrum broken off specimens illustrated in Figs. 1 , 2 ) and indented incisure; posterior, ventral, and dorsal margins evenly rounded in lateral view. Short indented line present with dorsal end just posterior to midheight of incisure and ventral end at anteroventral valve edge ventral to incisure (Figs. 1,2). Valves of specimens in collection are the actual shells, not inner molds.

Central adductor muscle scars: Numerous radiating scars; long axis of scar­complex slightly slanted with dorsal end slightly posterior to ventral end.

Carapace size (Table 2): Maximum length 9.1 mm, maximum height 7.6 mm.

Holes in carapace: Specimen illustrated in Fig. 1 A–E contains several round holes or pits (could not ascertain with certainty whether or not shell was completely penetrated) in the carapace. Holes or pits were observed in 2 of 16 valves examined (MAB k. 2407: 5 holes, 2418: 1 hole). Rims of holes do not appear to be raised or indented, but consist of an etched circle. Holes in a carapace may be formed by a boring organism, such as a naticid or muricid gastropod, for which the ichnogenus Oichnus Bromley 1981 is available (see discussions in Bromley 1981, 1993; Nielsen & Nielsen 2001, and Donovan & Jagt 2002). According to Reyment et al. (1987:192): “In relatively thin­shelled prey, such as ostracods, it is not always possible to identify the group to which the predator belonged.” The origin of the holes in the valves of M. hollandica is unknown, but they may have been made by a boring predator. Although bored holes are fairly common in valves of podocopid ostracodes ( Maddocks 1988:637; Reyment & Elewa 2003:96), they have not been reported previously in myodocopids.

Comparisons

Same as for genus.

Table 2. Parameters of Mesoleberis hollandica new genus and new species.

MAB = Oertijdmuseum De Groene Poort, NHMM = Natuurhistorisch Museum Maastricht, USNM = National Museum of Natural History. Specimen MAB k. 2407 holotype; other specimens paratypes.

Figures

FIGURE 1. Mesoleberis hollandica, new genus and new species: MAB k. 2407, holotype, A – E, left valve, length 9 mm. MAB k. 2417, paratype, F, G, right valve. Small white arrows on B and C point to linear indentation in carapace. White triangle just ventral to B indicates orientation (oblique ventrolateral view) of C.

FIGURE 2. Mesoleberis hollandica, new genus and new species: MAB k. 2410, paratype, A, B, left valve. MAB k. 2408, paratype, C – F, left valve. Small white arrows on D – F point to linear indentation in carapace. White triangles labeled E and F on C indicate orientation (oblique ventrolateral and anterolateral views) respectively of E and F.