Hypotetragona sp., Morey, 1935

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 : 20-21

Hypotetragona sp.

Fig. 6J–M

Indivisia minata – Song & Gong, 2019: fig. 4t.

Material examined

CHINA • 1 complete carapace (Ad, Fig. 6J ); Blue Snake section, Tangbagou Formation, sample 19BAI 39; Tournaisian, early Carboniferous; P6M 3865 • 1 complete carapace (A-1, Fig. 6K ); Blue Snake section, Tangbagou Formation, sample 19BAI 05; Tournaisian, early Carboniferous; P6M 3866 • 1 complete carapace (A-2, Fig. 6L ); Blue Snake section, Gelaohe Formation, sample 19BAI 60; Famennian, late Devonian; P6M 3867 • 1 complete carapace (A-3, Fig. 6M ); Blue Snake section, Gelaohe Formation, sample 19BAI 69; Famennian, late Devonian; P6M 3868 • 37 complete carapaces; Blue Snake section, Gelaohe and Tangbagou Formations, samples 19BAI 37, 19BAI 41, 19BAI 44, 19BAI 54, 19BAI 60, 19BAI 68, 19BAI 69; Famennian–Tournaisian, late Devonian–early Carboniferous.

Dimensions

RV: L = 302–846 µm, H = 198–519µm, H/L = 0.57–0.7.

LV: L = 299–834 µm, H = 195–509µm, H/L = 0.56–0.65.

Remarks

The adults of this species are represented by poorly preserved specimens that do not allow for a precise specific attribution. Indivisia minata Wei, 1988 in Song & Gong (2019) from the Famennian, late Devonian, of Blue Snake section, Guizhou, South China ( Song & Gong 2019) differs from Indivisia minata which is stockier, has a more rounded outline, an ADB which is not truncated and a less compressed laterally posterior part in LV. Indivisia minata in Song & Gong (2019) furthermore does not belong to the genus Indivisia Zaspelova, 1954 as shown by the deep sulcus and prominent lobe in the antero–dorsal part of the carapace. It has the typical outline of the family Geisinidae and displays the diagnostic lobes and sulcus of the genus Hypotetragona . It is morphologically similar to Hypotetragona sp. and is considered as conspecific. The specimen shown in Song & Gong (2019) is a steinkern which would explain the absence of ornamentation which is visible in well–preserved juveniles in our material. The size and the H/L ratio of the specimens shown in Song & Gong (2019) are similar to our material. At least 4 ontogenetic stages are present in our material. The ontogenetic development of this species is marked by the outline becoming more rectangular, the sulcus becoming deeper and lobes more developed.

Occurrence

Gelaohe Formation, Blue Snake section, Guizhou, South China, Famennian, late Devonian, ( Song & Gong 2019). Samples 19BAI 05, 19BAI 37, 19BAI 39, 19BAI 41, 19BAI 44, 19BAI 54, 19BAI 60, 19BAI 68, 19BAI 69, Gelaohe and Tangbagou Formations, Blue Snake section, Guizhou, South China, Famennian–Tournaisian, late Devonian–early Carboniferous (this work).

Figures

Fig. 6. 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. Kloedenellitina sincera Tschigova, 1960, left lateral view of a carapace, sample 19BAI 69 (P6M 3856). B–C. Kloedenellitina spinosa Gurevitch, 1972. B. ♀, right lateral view of a carapace, sample 19BAI 60 (P6M 3857). C. ♂, right lateral view of a carapace, sample 19BAI 69 (P6M 3858). D. Kloedenellitina sygmaeformis Egorov, 1950, right lateral view of a carapace, sample 19BAI 80 (P6M 3859). E. Blessites feluyensis Tschigova, 1977, right lateral view of a carapace, sample 19BAI 39 (P6M 3860). F–I. Hypotetragona angulata (Posner, 1951). F. Adult, left lateral view of a carapace, sample 19BAI 44 (P6M 3861). G. A-1, left lateral view of a carapace, sample 19BAI 02 (P6M 3862). H. A-2, left lateral view of a carapace, sample 19BAI 02 (P6M 3863). I. A-3, left lateral view of a carapace, sample 19BAI 03 (P6M 3864). J–M. Hypotetragona sp. J. Adult, left lateral view of a carapace, sample 19BAI 39 (P6M 3865). K. A-1, left lateral view of a carapace, sample 19BAI 05 (P6M 3866). L. A-2, left lateral view of a carapace, sample 19BAI 60 (P6M 3867). M. A-3, left lateral view of a carapace, sample 19BAI 69 (P6M 3868). N. Knoxiella archedensis Tschigova, 1960, left lateral view of a carapace, sample 19BAI 03 (P6M 3869). O. Knoxiella complanata (Kummerow, 1939), left lateral view of a carapace, sample 19BAI 80 (P6M 3870). P. Knoxiella subcompressa, Wang & Ma, 2007, left lateral view of a carapace, sample 19BAI 68 (P6M 3871). Q–R. Knoxiella cf. subcompressa, Wang & Ma, 2007. Q. Adult, left lateral view of a carapace, sample 19BAI 68 (P6M 3871). R. A-1, left lateral view of a carapace, sample 19BAI 68 (P6M 3872). S–T. Knoxina sp. S. Left lateral view of a carapace, sample 19BAI 80 (P6M 3873). T. Left lateral view of a carapace, sample 19BAI 74 (P6M 3874). U. Knoxites cf. argulata Zaspelova, 1959, adult, left lateral view of a carapace, sample 19BAI 02 (P6M 3875). Scale bars = 100 µm.