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Issue: Vol. 5796 No. 1: 20 Apr. 2026
Type: Article
Published: 2026-04-20
DOI: 10.11646/zootaxa.5796.1.5
Page range: 95-123
Abstract views: 117
PDF downloaded: 8

Morphological variation of the Bicornucythere bisanensis complex (Ostracoda, Crustacea), with a description of a new species

Shanghai Natural History Museum (branch of Shanghai Science and Technology Museum); 510 West Beijing Road; Jing’an District; Shanghai 200041; China; Shanghai Mineral Fossil Association; 66 Xianfeng Street; Minhang District; Shanghai 201103; China
State Key Laboratory of Palaeobiology and Stratigraphy; Nanjing Institute of Geology and Palaeontology; Chinese Academy of Sciences; 39 East Beijing Road; Xuanwu District; Nanjing 210008; China
State Key Laboratory of Marine Geology; Tongji University; 1239 Siping Road; Yangpu District; Shanghai 200092; China
Shanghai Natural History Museum (branch of Shanghai Science and Technology Museum); 510 West Beijing Road; Jing’an District; Shanghai 200041; China
State Key Laboratory of Palaeobiology and Stratigraphy; Nanjing Institute of Geology and Palaeontology; Chinese Academy of Sciences; 39 East Beijing Road; Xuanwu District; Nanjing 210008; China; Shanghai Natural History Museum (branch of Shanghai Science and Technology Museum); 510 West Beijing Road; Jing’an District; Shanghai 200041; China
Crustacea East China Sea Bicornucythere zhaoi sp. nov. ontogenetic changes fossae arrangement pattern paedomorphosis

Abstract

The Bicornucythere bisanensis complex is a species group of trachyleberidid Ostracoda found in shallow-sea sediments along the margin of the East China Sea, which contains three members, namely Bicornucythere bisanensis, B. misumiensis, and Form G. In this study, we analyzed the ontogenetic changes in carapace morphology of B. bisanensis and Form G from the East China Sea and compared them with the specimens of the B. bisanensis complex from the South Yellow Sea, the Leizhou Peninsula, and those in the published literatures, in order to reveal the similarities and differences between the three members. Our results indicate that Form G resembles the young instars of B. bisanensis in carapace size, shape and the fossae arrangement pattern (FAP) on the carapace surface. Our results also show significant differences between Form G and the other two members; B. bisanensis and B. misumiensis share a relatively large carapace size (L=0.66–0.95 mm), a sub-rectangular lateral outline and the same FAP, whilst Form G has a small, sub-triangular carapace (L=0.51–0.66 mm) and a FAP with nine fewer fossae. We concluded that the sub-triangular carapace outline and the peculiar FAP in Form G are species-specific, and we described Form G as a new species, Bicornucythere zhaoi sp. nov.

A few individuals with small, sub-triangular valves and an intermediate type of FAP between B. bisanensis and B. zhaoi sp. nov., which were tentatively named Bicornucythere aff. zhaoi, were discovered from the Pliocene Leizhou Peninsula where it co-occurred with B. bisanensis. Their occurrence may suggest that the latecomer B. zhaoi sp. nov., which does not appear until late Pleistocene, is descended from B. bisanensis by paedomorphosis.

 

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How to Cite

Wang, Y., Wang, Y., Fan, D., Miao, K. & Zhou, B. (2026) Morphological variation of the Bicornucythere bisanensis complex (Ostracoda, Crustacea), with a description of a new species. Zootaxa, 5796 (1), 95–123. https://doi.org/10.11646/zootaxa.5796.1.5