Parabrachidontes Tan, Tan, Sanpanich, Duangdee & Ambarwati, 2024

Tan, Koh Siang, , Samuel Hui Ming Tan, , Kitithorn Sanpanich, , Teerapong Duangdee, Ambarwati, & Reni, 2024, Validation of Parabrachidontes, a new genus of fresh- and brackish-water mussels (Bivalvia: Mytilidae) from Southeast Asia with a redescription of the type species and P. amnicus Tan et al., 2023, Raffles Bulletin of Zoology 72, pp. 214-218 : 215

Parabrachidontes Tan, Tan, Sanpanich, Duangdee & Ambarwati , new genus

Type species: Modiola leucosticta von Martens, 1897: 86–88 (see below); by present designation.

ZooBank registration: urn:lsid:zoobank.org:act:EB33F9A1-3627-4E3D-A639-7D1A921CF36F and urn:lsid:zoobank.org:act:7DA9F849-ED7E-429E-A0C9-DAF3FFD9D7C8

Diagnosis. Adult shell up to 30 mm in length, mytiliform to modioliform in outline, equivalve; shell surface generally either greenish-brown or dark brown to black, entirely smooth or bearing weak to strong radial ribs, often with closely set commarginal lines. Umbones generally subterminal. Shell interior iridescent; linear series of small teeth are present on the inside edge of shell margins anterior (about 12 elongate, closely-set teeth) and posterior (about 7 papillate crenules) to the ligament. Ligament internal, narrow, resilial pits absent. Posterior adductor muscle scar confluent with single, narrow posterior byssal retractor muscle scar. Ascending lamella of outer demibranch on either side of animal is shorter than descending lamella; terminal (upper) edge of the ascending lamella fused to the adjacent mantle lobe surface. Ascending lamella of inner demibranch may also be fused to the mantle surface of the visceral mass. Plicate glands are absent. The pericardium is located between the anterior and posterior sets of the posterior byssal retractor muscle complex (Category 3 of Morton, 2015). Currently, the new genus comprises three species distributed variously in India, peninsular Thailand, Singapore, Sarawak (east Malaysia) and Sulawesi ( Indonesia). Two of the three species occur in salinities below 3 psu.