Candonidae, Kaufmann, 1900

Wang, Yaqiong, 2025, First report of the non-marine ostracod fauna from the Lower Cretaceous Xiaonangou Formation of the Baishan Basin, NE China, Zootaxa 5660 (4), pp. 560-572 : 566-569

Candonidae gen. indet. sp.

Figs. 2 , 5C–J .

Material. Ten carapaces. Dimensions. L: 0.40–0.47 mm, H: 0.22–0.28 mm, W: 0.16–0.19 mm.

Description. Small sized carapace with thin-shelled and a long-oval shape in lateral view. Maximum length at 1/2 of height, maximum height at middle of maximum length, and maximum width at mid-length. LV larger than RV; LV overlapping RV along all margins, with strong valve overlapping in ventral area. Both anterior and posterior margins equicurvate and rounded. Surface smooth.

Remarks. In China, numerous studies have classified ostracod specimens similar to the specimens of this study, characterized by a small, thin-shelled, long-oval carapace shape, with the LV overlapping RV along all margins and both anterior and posterior margins rounded, under the genus Candoniella Schneider, 1956 (e.g., Zhang 1985, 1987; Ye et al. 2002; see Hou et al. 2002 for a review). However, Danielopol et al. (2022) argue that the genus Candoniella Schneider, 1956 is an invalid genus and that it represents a taxonomic chimera, an artifact in which juveniles of species from different Candoninae genera are amalgamated into a single taxon. It implies that all described Candoniella species require a comprehensive reassessment; to address this problem, more detailed taxonomic work and a wide morphological analysis of all specimens from the genus Candoniella are required, however, is out of our topic of present work. The studied specimens may represent juvenile individuals of a certain Candoninae genus or species. However, due to the limited number of specimens and the lack of evidence for continuous morphological changes during ontogeny, they can only be identified to the family level without determining the genus and species.

Figures

FIGURE 2. Stratigraphic column for the ostracod-bearing sequence in the Guanghuanjie-Yumuqiaozi section (41°56'34.4"N, 126°34'18.6"E) of the Baishan Basin, showing the positions of the ostracod samples and abundances of ostracod species recovered from the Xiaonangou Formation.

FIGURE 5. A–B. Candona praevara Zhang & Zhang, 1982, A, left lateral view of carapace (NIGP 206928), sample 2024- XNG-10A, B, right lateral view of carapace (NIGP 206928), sample 2024-XNG-10A; C–J. Candonidae gen. indet. sp., C, left lateral view of carapace (NIGP 206929), sample 2024-XNG-11, D, right lateral view of carapace (NIGP 206929), sample 2024- XNG-11, E, right lateral view of carapace (NIGP 206930), sample 2024-XNG-11, F, ventral view of carapace, anterior to left (NIGP 206930), sample 2024-XNG-11, G, right lateral view of carapace (NIGP 206931), sample 2024-XNG-11, H, dorsal view of carapace, anterior to left, (NIGP 206931), sample 2024-XNG-11, I, right lateral view of carapace (NIGP 206932), sample 2024-XNG-11, J, left lateral view of carapace (NIGP 206932), sample 2024-XNG-11; K–R. Cyclocypris invalida Zhang, 1985, K, right lateral view of carapace (NIGP 206933), sample 2024-XNG-11, L, left lateral view of carapace (NIGP 206933), sample 2024-XNG-11, M, left lateral view of carapace (NIGP 206934), sample 2024-XNG-11, N, right lateral view of carapace (NIGP 206934), sample 2024-XNG-11, O, ventral view of carapace, anterior to left (NIGP 206935), sample 2024-XNG-11, P, dorsal view of carapace, anterior to left (NIGP 206935), sample 2024-XNG-11, Q, left lateral view of carapace with anterior part of shell missing (NIGP 206936), sample 2024-XNG-11, R, right lateral view of carapace (NIGP 206936), sample 2024-XNG-11. Scale bars = 100 μm.