Bairdia (Rectobairdia) chalonensis, Casier & Olempska, 2008

Casier, Jean-Georges & Olempska, Ewa, 2008, Early Frasnian ostracods from the Arche quarry (Dinant Synclinorium, Belgium) and the Palmatolepis punctata Isotopic Event, Acta Palaeontologica Polonica 53 (4), pp. 635-646 : 640-643

Bairdia (Rectobairdia) chalonensis sp. nov.

Fig. 4M–O .

Etymology: After type horizon.

Holotype: IRScNB n° b5083. Carapace. AR−06−23. Fig. 4M 1 , M 2. L = 1.19 mm; H = 0.62mm; W = 0.44 mm.

Type locality: Access path to the Arche quarry.

Type horizon: Chalon Member of the Moulin Liénaux Formation, Early Frasnian, Devonian.

Diagnosis.—Large and elongate, with an anterior extremity at two−third of the height, posterior point above midheight, dorsal margin straight to gently curved, median part of carapace finely pitted.

Material.—76 valves and carapaces (samples AR−06−17?, 20?, 22?, 23, 24, 26–28, 31).

Description.—Large and elongate Bairdia (Rectobairdia) , with a nearly straight dorsal border parallel to the slightly concave ventral border. Dorsal part of the anterior border slightly concave and moderately inclined, and ventral part well rounded with an extremity forming a right angle at two−third of the height. Dorsal part of the posterior border also slightly concave but more inclined, and ventral part moderately curved with an acuminate extremity at mid−height. Greatest length at mid−height and greatest height at mid−length. The left valve is larger than the right, but their contours are similar except for the straight ventral border. In right lateral view, the left valve projects all along the free margin except in the antero−ventral sector. In dorsal view, the valves are symmetric, convex but slightly concave close to the acuminate extremities. The greatest width is at mid−length. The hinge line is sinuous. In ventral view, the right valve is flat very close to the ventral margin, and the overlap of the left valve on the right is the greatest before the mid−length. Surface of the valves finely pitted.

2

Remarks.— Bairdia (Rectobairdia) sp. A of Becker (1971) from the Boussu−en−Fagne Member of the Grand Breux Formation exposed in the access path to the Lion quarry, at Frasnes, may belong to or be very close to B. (R.) chalonensis . The morphology of the carapace is the same in the two species except that the specimens collected by Becker (1971) are smooth.

Figures

Fig. 4. Early Frasnian ostracods from the access path to the Arche quarry, Dinant Synclinorium, Belgium. A. Jenningsina lethiersi Becker, 1971. Poorly preserved carapace in right lateral view. Sample AR−06−26. IRScNB n° b5071. B. Favulella lecomptei Becker, 1971. Carapace in right (B1) and dorsal (B2) views. Sample AR−06−26. IRScNB n° b5072. C. Bairdiocypris sp. 5 sensu Magne (1964). Poorly preserved carapace in right (C) and ventral (C) views. Sample 1 2 AR−06−17. IRScNB n° b5073. D, E. Bairdiocypris sp. C. D. Broken carapace in right lateral view. Sample AR−06−26.IRScNB n° b5074. E. Broken carapace in dorsal view. Sample AR−06−26. IRScNB n° b5075. F–J. Microcheilinella archensis sp. nov. F. Carapace in right lateral (F) and dorsal (F) views. Sample 1 2 AR−06−26. IRScNB n° b5076. G. Holotype. Carapace in right lateral view. Sample AR−06−27. IRScNB n° b5077. H. Carapace in right lateral view. Sample AR−06−28. IRScNB n° b5078. I. Ventral view of a carapace. Sample AR−06−27. IRScNB n° b5079. J. Anterior (J) and posterior (J) views of a carapace. Sam1 2 ple AR−06−28. IRScNB n° b5080. K. Healdianella? sp. B in Becker (1971). Carapace in right (K) and dorsal (K) views. Sample AR−06−28.IRScNB n° b5081. 1 2 L. Bairdia (Rectobairdia) paffrathensis Kummerow, 1953.Poorly preserved carapace in right lateral view. Sample AR−06−23.IRScNB n° b5082. M–O. Bairdia (Rectobairdia) chalonensis sp. nov. M. Holotype. Carapace in right lateral (M) and dorsal (M) views. Sample AR−06−23. IRScNB n° b5083. N. Carapace in 1 2 right lateral view. Sample AR−06−26. IRScNB n° b5084. O. Carapace in right lateral view. Sample AR−06−26. IRScNB n° b5085. Scale bars 200 µm.

Fig. 1. Locality map of the Arche quarry, the Lion quarry and the Frasnes railway section; the access path to the Arche quarry indicated by arrow.

Fig. 2. Lithologic sections of the Chalon Member and of the extreme base of the Arche Member exposed on the north−eastern side and on the south−eastern side of the access path to the Arche quarry.