Bairdianella cuspis Buschmina, 1970

Guillam, Elvis, Forel, Marie-Béatrice, Song, Junjun & Crasquin, Sylvie, 2022, Late Devonian-early Carboniferous ostracods (Crustacea) from South China: taxonomy, diversity and implications, European Journal of Taxonomy 804, pp. 1-62 : 36-37

Bairdianella cuspis Buschmina, 1970

Fig. 11P

Bairdianella cuspis Buschmina, 1970: 73 , pl. V fig. 2.

Bairdianella cuspis – Kotschetkova & Janbulatova 1987: pl. 24 fig. 1. — Zhuravlev & Sobolev 2019: figs 4i–j. – Sobolev 2020: figs 5–10.

Material examined

CHINA • 1 complete carapace ( Fig. 11P ); Blue Snake section, Tangbagou Formation, sample 19BAI 03; P6M 3973 • 25 complete carapaces; Blue Snake section, Tangbagou Formation, samples 19BAI 01-03, 19BAI 05, 19BAI 37, 19BAI 39, 19BAI 44. All from the Tournaisian, early Carboniferous.

Dimensions

RV: L = 460–575µm, H = 188–247µm, H/L = 0.37–0.45.

LV: L = 460–587 µm, H = 201–255 µm, H/L = 0.38–0.48.

Remarks

Our material is smaller than the holotype shown in Buschmina (1970: pl: 5 fig. 2) with L = 625µm, H = 325 µm, H/L = 0.52. Specimens shown in Kotschetkova & Janbulatova (1987: pl. 24 fig. 1) from Mugodzhary, Western Kazakhstan and Sobolev (2020: figs 5, 9–10)) from Pechora Uplift, Russia, have a similar size to our material with respectively L = 532µm, H = 250 µm and H/L = 0.47 and L = 580µm, H = 280 µm, H/L = 0.48. However, the specimen shown in Zhuravlev & Sobolev (2019) from North Ural is slightly larger than the present material with L = 580µm, H = 275µm and H/L = 0.47 but still smaller than the holotype in Buschmina (1970). The size variations in our material indicate that at least two stages are present and may correspond to juveniles, compare to the holotype in Buschmina (1970), but the wide distribution of the dimensions of the specimens does not allow to clearly discriminate them.

Five species have been mentioned as Bairdianella aff. cuspis in papers discussing Devonian– Carboniferous ostracod faunas, they are summarized in Table 3 .

Based on specimens shown in these different contributions, the main differences between these species and Bairdianella cuspis Buschmina, 1970 seem to be weak variations of the length of the carapace, concavity at VB, degree of postero-dorsal angulation, posterior end more or less rounded and AVB sometimes truncated (visible only on Bairdianella sp. A , aff. cuspis Buschmina, 1970 in Casier et al. 2004). Specimens of Bairdianella aff. cuspis Buschmina, 1970 sensu Kotschetkova & Janbulatova 1987 in Casier et al. (2002), Bairdianella sp. A , aff. cuspis Buschmina, 1970 in Casier & Préat (2003) and Bairdianella sp. B , aff. cuspis Buschmina, 1970 in Casier et al. (2004) are also larger than the holotype but others had sizes similar to our material so may also correspond to juveniles. These differences do not seem sufficient to reasonably distinguish these forms from the species described by Buschmina (1970). However, only one specimen is shown in each of these papers with no discussion on possible other specimens, ontogenetic and intraspecific variations within the material or comparisons between these different species. Only a complete review of these taxa, based on close observations of all these specimens, can clarify this major issue. For this reason, they are kept as distinct species.

Occurrence

Gengis horizon, Yeltsov synclinorium, South of Occidental Siberia, early Carboniferous ( Buschmina 1970). Berchogur section, Mugodzhary, Western Kazakhstan, Devonian–Carboniferous transition ( Kotschetkova & Janbulatova 1987). Kamenka River section, North Urals, Russia, Famennian– Tournaisian, late Devonian–early Carboniferous ( Zhuravlev & Sobolev 2019). Yjid-Kamenka river section, Pechora Uplift, Russia, Famennian–Tournaisian, late Devonian–early Carboniferous ( Sobolev 2020). Samples 19BAI 01-03, 19BAI 05, 19BAI 37, 19BAI 39, 19BAI 44, Tangbagou Formation, Blue Snake section, Tournaisian, early Carboniferous (this work).

Figures

Fig. 11. SEM pictures of ostracods from Blue Snake section, Dushan County, South China, late Famennian–Tournaisian, late Devonian–early Carboniferous. All specimens are temporarily housed in the collections of Sorbonne Université, Paris, France (SU). A. Bairdia sp. 4, right lateral view of a carapace, sample 19BAI 08 (P6M 3958). B. Bairdia sp. 5, right lateral view of a carapace, sample 19BAI 03 (P6M 3859). C. Bairdia sp. 6, right lateral view of a carapace, sample 19BAI 03 (P6M 3960). D. Bairdia sp. 7, right lateral view of a carapace, sample 19BAI 23 (P6M 3961). E. Bairdia (Cryptobairdia) cf. curta McCoy, 1844 emend. Jones & Kirkby, 1878 in Crasquin, 1986, right lateral view of a carapace, sample 19BAI 60 (P6M 3962). F. Bairdia (Cryptobairdia) lavenei Crasquin, 1985, right lateral view of a carapace, sample 19BAI 03 (P6M 3963). G. Bairdia (Rectobairdia) angulatiformis Posner, 1951, right lateral view of a carapace, sample 19BAI 67 (P6M 3964). H. Bairdia (Rectobairdia) buschminae Crasquin, 1985, right lateral view of a carapace, sample 19BAI 08 (P6M 3965). I. Bairdia (Rectobairdia) cf. plebeja Reuss, 1854, right lateral view of a carapace, sample 19BAI 03 (P6M 3966). J–L. Bairdia (Rectobairdia) sp. cf. R. sinuosa (Morey, 1936) in Crasquin, 1985. J. Right lateral view of a carapace, sample 19BAI 01 (P6M 3967). K. Right lateral view of a carapace, sample 19BAI 02 (P6M 3968). L. Right lateral view of a carapace, sample 19BAI 60 (P6M 3969). M. Bairdiacypris nanbiancunensis Wang, 1988, right lateral view of a carapace, sample 19BAI 60 (P6M 3970). N. Bairdiacypris quasielongata Buschimna, 1968, right lateral view of a carapace, sample 19BAI 01 (P6M 3971). O. Bairdiacypris subcylindrica Buschimna, 1984, right lateral view of a carapace, sample 19BAI 58 (P6M 3972). P. Bairdianella cuspis Buschmina, 1970, right lateral view of a carapace, sample 19BAI 03 (P6M 3973). Q. Fabalicypris sundarijanata Wang & Cao, 1997 in Song & Gong, 2019, right lateral view of a carapace, sample 19BAI 67 (P6M 3974). R. Bairdiodea? indet. Left lateral view of a carapace, sample 19BAI 63 (P6M 3975). Scale bars = 100µm.