Diaurora aurorea (Heude, 1883)

Chen, Zhong-Guang, Dai, Yu-Ting, Ouyang, Shan, Huang, Xiao-Chen & Wu, Xiao-Ping, 2023, Unveiling the identity of Diaurora Cockerell, 1903 (Bivalvia, Unionidae): morphology, molecular phylogenetics, and the description of a new species, ZooKeys 1173, pp. 131-144 : 131

Diaurora aurorea (Heude, 1883)

Figs 3A , 4A , 5A

Museum material.

Holotype: USNM472411, Ning-kouo hien [宁国县], Kien-té hien [建德县], China. NZMC FM00732, Yuanjiang River [沅江], Hunan Province [湖南省], China. SMF24000 a-b, Yütanchiao [玉潭桥], Hunan [湖南], China, 28°15′7″N, 112°33′45″E.

New material.

22_NCU_XPWU_DA01-02, Fuhe River [抚河], Fuzhou City [抚州市], Jiangxi Province [江西省], China, 27°53′57″N, 116°34′03″E, collected by Zhong-Guang Chen, Yu-Ting Dai, Chen-Chen Jia & Ying-Ying Zhang in September 2022. 22_NCU_XPWU_DA03-15, Ganjiang River [赣江], Jian City [吉安市], Jiangxi Province [江西省], China, 27°12′39″N, 115°09′44″E, collected by Zhong-Guang Chen & Zheng-Jie Lou in November 2022. YHC0028001, Jiulong River [九龙江], Fujian Province [福建省], China, collected by Hao Yang in 2003 .

Diagnosis.

Shell triangular-ovate; posterior margin obliquely arc-shaped. Periostracum with straight broken blackish-green rays. Zigzag sculpture presented on all over the shell surface.

Description.

Shell (Figs 3A , 4A ). Shell small size, symmetric, solid, moderately thick, sub-glossy, triangular-ovate. Anterior margin oval, inflated; dorsal margin curved downwards; ventral margin slightly rounded or nearly straight; posterior margin obliquely arc-shaped. Umbo inflated, above hinge line, located at 1/3 of the dorsal margin, and often eroded. Periostracum orangish to brownish, with straight broken blackish-green rays and thin growth lines. Growth lines arranged in irregular concentric circles. Zigzag sculpture presented on all over the shell surface but weakening from umbo to edge. Hinge short. Ligament short and strong. Mantle muscle scars obvious. Anterior adductor muscle scars oval, deep, smooth in junior but rough in adult; posterior adductor muscle scars long oval, smooth. Left valve with two pseudocardinal teeth, equal height, anterior tooth small and flat, posterior tooth thick and pyramidal; anterior pseudocardinal tooth of the right valve well developed, posterior pseudocardinal tooth reduced, connected to lateral teeth. Lateral teeth of both valves long and thick. Nacre white or light orangish.

Length 32.0-41.3 mm, height 20.5-26.0 mm, width 12.4-17.2 mm.

Soft anatomy (Fig. 5A ). Mantle off-white to light-brownish, aperture margins brown, flap margin with blackish to brown papillae. Gills light-brownish, inner gills slightly longer and wider than outer gills. Labial palps yellowish to brown (fade to grayish white in alcohol), distally pointed and irregularly fan-shaped in appearance. Visceral mass creamy white, foot orange (fade to grayish white in alcohol).

Vernacular name.

金黄蚌 (Pinyin: jin huang bang).

Distribution and ecology.

Scattered in the middle and lower Changjiang River basin and the upper Jiulongjiang River, including Anhui Province, Jiangxi Province, Hunan Province and Fujian Province (Fig. 6 ). It mainly co-occurs with Aculamprotula polysticta (Heude, 1877), Acuticosta chinensis (Lea, 1868), Cuneopsis heudei (Heude, 1874), Nodularia douglasiae (Gray, 1833), Lamprotula caveata (Heude, 1877), Lanceolaria triformis (Heude, 1877) and Ptychorhynchus pfisteri (Heude, 1874) in the sandy substrates of tributaries of large rivers (Fig. 7 ). Besides, D. aurorea was reported in Vietnam by Dang et al. (1980), but the specimens were not available for examination ( Do et al. 2018). This record is highly dubious due to its considerable distance from the known distribution range of D. aurorea as documented in this study. It is possible that this record was a misidentification of Acuticosta species.

Remarks.

The rarity of D. aurorea has been seriously underestimated for a long time due to the common misidentification of museum material. Upon examination of museum specimens, it has been discovered that specimen NZMC10542 in the National Zoological Museum of China and specimens 15_NCU_XPWU_AA01-11 in Nanchang University were actually Acuticosta chinensis . Since its original description, only a handful of additional specimens of D. aurorea have been correctly identified. It has always been shrouded in mystery as there are hardly any photographs of specimens other than the type specimen. The new specimens examined in this study indicate that it is far more widespread than previously recorded. However, the habitats of D. aurorea are severely fragmented and the population size is very small. Therefore, it requires more attention and protection in the future.

Figures

Figure 3. Specimens of Diaurora and Acuticosta chinensis A Diaurora aurorea, 22 _ NCU _ XPWU _ DA 03 B Diaurora laeve sp. nov., holotype: 22 _ NCU _ XPWU _ DL 01 C Acuticosta chinensis, 22 _ NCU _ XPWU _ AC 01.

Figure 4. Comparison of the radial pattern on the shell surface in Diaurora A Diaurora aurorea, 22 _ NCU _ XPWU _ DA 04 B Diaurora laeve sp. nov., 22 _ NCU _ XPWU _ DL 02.

Figure 5. Soft anatomical characters of Diaurora A Diaurora aurorea, 22 _ NCU _ XPWU _ DA 15 B Diaurora laeve sp. nov., 22 _ NCU _ XPWU _ DL 50. aam, anterior adductor muscle; pam, posterior adductor muscle; ea, excurrent aperture; ia, incurrent aperture; pia, papillae of the incurrent aperture; pea, papillae of the excurrent aperture; ig, inner gills; og, outer gills; m, mantle; lp, labial palps; vm, visceral mass; f, foot.

Figure 6. Distribution map of Diaurora. Star: type locality of Diaurora laeve sp. nov.; solid triangle: type locality of Diaurora aurorea; hollow triangle: new locality of Diaurora aurorea.

Figure 7. Habitat of Diaurora. A habitat of Diaurora aurorea, Fuhe River, Fuzhou City, Jiangxi Province, China B habitat of Diaurora laeve sp. nov., Zishui River, Shaoyang City, Hunan Province, China.