Ctenodesma bersinara Zieritz et al., sp. nov.

Zieritz, Alexandra, Pfeiffer, John, Rahim, Khairul Adha A., Prayogo, Hari, Anwari, Muhammad Sofwan, Diba, Farah, Froufe, Elsa, Blackwell, Tabitha, Hartikainen, Hanna & Lopes-Lima, Manuel, 2024, High endemic freshwater mussel (Bivalvia: Unionida) diversity in western Borneo, with description of three new species, Zoological Journal of the Linnean Society 201, pp. 1-15 : 9-11

Ctenodesma bersinara Zieritz et al., sp. nov.

( Fig. 4 )

Type locality: Sungai Rempangi (Pawan Drainage), 17 km SSW of Randau, Ketapang Regency, West Kalimantan, Indonesia ( Fig. 5B ).

Type: Holotype, FKH_MFw_x541.

Material examined: One lot: FKH_MFw_x541.

Diagnosis: Morphologically very similar to other Ctenodesma species but is less elongate, has a sharper posterior ridge, and strong green rays on posterior slope and shell disk.

Description: Shell thin, with fine wrinkles extending from posterior ridge, fine sculpture on dorsal third of shell disk; subrhombodial shell outline with slightly biangulate posterior slope; ventral margin slightly rounded, dorsal margin angled upwards, umbo even with hinge line; periostracum yellowish brown with green rays of variable thickness. Pseudocardinal teeth, elongate, moderately thick, one tooth in left valve, two teeth in right valve. Lateral teeth long, straight, two in left valve, one in right valve; Nacre bluish white, with yellowish brown tint near umbo and posterior slope. Soft anatomy unavailable for study.

Distribution: Known only from the type locality in West Kalimantan ( Fig. 5B ).

Etymology: The species is named after its strong green rays using the Bahasa Indonesian word ‘ bersinar ’, meaning ‘radiating’.

Remarks: This species is known from a single small specimen (~ 40 mm), making meaningful morphological description of the species very difficult.

Figures

Figure 4. Holotypes of Ctenodesma bersinara, Sungai Rempangi, Pawan River basin, West Kalimantan, Indonesian Borneo; Ctenodesma mawonae, Sungai Sebua Jebung, Sarawak River basin, Jambusan, Bau, Sarawak, Malaysian Borneo; and Rectidens lauris, Sungai Rempangi, Pawan River basin, West Kalimantan, Borneo. Abbreviations: FKH, Fahutan Kapuas Hulu Collection, Tanjungpura University, Indonesia; FRST, Faculty of Resource Science and Technology Collection, Universiti Malaysia Sarawak, Malaysia.

Figure 5. Images of type localities of (A) Ctenodesma mawonae, i.e. Sungai Sebua Jebung in the Sarawak River basin, Jambusan, Bau, Sarawak, Malaysian Borneo, and (B) Ctenodesma bersinara and Rectidens lauris, i.e. Sungai Rempangi, Pawan River basin, West Kalimantan, Indonesian Borneo.