Ctenodesma mawonae Zieritz et al.

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 : 11-12

Ctenodesma mawonae Zieritz et al. , sp. nov.

( Fig. 4 )

Type locality: Sungai Sebua Jebung ( Sarawak Drainage), 3 km SSW of Bau, Kuching division, Sarawak, Malaysian Borneo ( Fig. 5A ).

Type: Holotype, FRST_MFw_x675. Paratype, FRST_MFwx674, same locality as holotype.

Material examined: Five lots: FRST_MFw_x675, FRST_MFw_ x674, MNHN MP 2723, MCZ 174117, BMNH MP D022.

Diagnosis: Morphologically very similar to other Ctenodesma species but is more elongate and has a less developed posterior ridge.

Description: Shell thin, with fine wrinkles extending from posterior ridge, fine sculpture on dorsal third of shell disk; elliptical shell outline with slightly biangulate posterior slope; ventral margin slightly rounded, dorsal margin angled slightly upwards; umbo slightly elevated above hinge line; periostracum brown to yellow, with or without green rays of variable thickness. Pseudocardinal teeth, thick, fractured, one tooth in left valve, two teeth in right valve. Lateral teeth long, straight, two in left valve, one in right valve; Nacre blueish white, with peach tint near the umbo. Soft anatomy unavailable for study.

Distribution: Known from the type locality in Sarawak ( Fig. 5A ) and three lots from ‘Sarawak’.

Etymology: The species is named in honour of Ms Dora Mawon, an amateur naturalist belonging to the local indigenous Bidayuh tribe, who assisted us during fieldwork at the type locality.

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.