Bairdia adelineae, Forel, 2012

Forel, Marie-Béatrice, 2012, Ostracods (Crustacea) associated with microbialites across the Permian-Triassic boundary in Dajiang (Guizhou Province, South China), European Journal of Taxonomy 19, pp. 1-34 : 8-10

Bairdia adelineae sp. nov.

Fig. 3 N-Q

Diagnosis

Stocky species of Bairdia with strong dorsal overlap, laterally flattened plateau-like DB, AB and PB with large radius of curvature.

Etymology

Personal dedication to Adeline Bienvenu.

Material examined

Holotype

One carapace ( Fig. 3N ), sample 05PAJ42, collection number P6M2930.

Paratype

One carapace ( Fig. 3P ), sample 05PAJ42, collection number P6M2932.

Other material

4 carapaces, several fragments. The species is known from its type locality only.

Type locality

Daye Formation (Sample 05PAJ42), Dajiang section (25°33’56’’N- 106°39’41’’E), Guizhou Province, South China, Griesbachian, Early Triassic.

Measurements

L = 513 – 655 μm; H = 292 – 347 μm; H/L = 0.53 – 0.58.

Description

Carapace elongated and massive, subovoid in lateral view; surface smooth; carapace amplete to preplete; LV overlapping RV all around the carapace, dorsal overlap stronger than ventral one; dorsum subdivided into 3 distinct parts at both valves; PDB straight to slightly convex; DB straight at both valves, flattened laterally at RV; ADB straight to slightly concave at anterior extremity; DB and ADB longer than PDB; VB long and slightly concave in median part at RV, straight to slightly concave at LV; AVB broadly rounded and long (~ 75% of Hmax); PVB straight to convex and short (<50% of Hmax); AB rounded with large radius of curvature, maximum in the upper 1/3 of H, bairdian beak poorly expressed but distinct; PB pointed with large radius of curvature, maximum at or slightly below mid-H; in dorsal view, carapace lenticular and thick with anterior extremity slightly tapered, Wmax located around mid-L, plateau-like laterally flattened at RV.

Remarks

This new species can be related to Bairdia paussi Crasquin, 2010 from the Late Permian of the Meishan section, Zhejiang Province, South China ( Crasquin et al. 2010). However Bairdia adelineae sp. nov. is more elongated, with stronger overlap and posterior maximum of convexity located closer to VB. It can also be compared to Orthobairdia texana (Harlton, 1927) sensu Shi & Chen, 2002 from the Permian of Heshan and Yishan, Guangxi Province, South China ( Shi & Chen 2002). However, the bairdioid dorsal view precludes generic attribution to Orthobairdia . Bairdia adelineae sp.nov is also close to Bairdia chasae Kellett, 1934 sensu Wang, 1978 from the Late Permian of the Western Guizhou and Northeastern Yunnan Provinces, South China ( Wang 1978). However the new species has a less pointed PB, a thinner ventral overlap and the dorsal view clearly shows a bairdioid shape. It is noteworthy that Bairdia chasae Kellett, 1935 sensu Wang, 1978 seems wrongly attributed to the genus Bairdia : the dorsal view shows a typical orthobairdian shape.

Figures

Fig. 3. Ostracods from the Dajiang section, South China. — A–D. Acratia candyae sp. nov. A. Holotype, carapace, right lateral view, P6M2917. B. Carapace, dorsal view, P6M2918. C. Paratype, carapace, right lateral view, P6M2919. D. Carapace, right lateral view, P6M2920. — E–F. Acratia subfusiformis Wang, 1978. E. Carapace, right lateral view, P6M2921. F. Carapace, right lateral view, P6M2922. — G. Acratia? sp. 1, carapace, right lateral view, P6M2923. — H. Acratia? sp. 2, carapace, right lateral view, P6M2924. — I. Acratia? sp. 3, carapace, right lateral view, P6M2925. — J–K. Acratia sp. 4. J. Carapace, left lateral view, P6M2926. K. Carapace, right lateral view, P6M2927. — L. Acratia sp. 5, carapace, right lateral view, P6M2928. — M. Acratiidae indet., carapace, right lateral view, P6M2929. — N–Q. Bairdia adelineae sp. nov. N. Holotype, carapace, right lateral view, P6M2930. O. Carapace, dorsal view, P6M2931. P. paratype, carapace, right lateral view, P6M2932. Q. Carapace, right lateral view, P6M2933. — R–V. Bairdia gaelleae Crasquin, 2010. R. Carapace, dorsal view, P6M2934. S. Carapace, right lateral view, P6M2935. T. Carapace, left lateral view, P6M2936. U. Carapace, right lateral view, P6M2937. V. Carapace, right lateral view, P6M2938. – Scale = 100 µm.