taxonID	type	description	language	source
B4A368D346145DE8B232C68F9B452625.taxon	description	Figs 1, 3, 4 A, B	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
B4A368D346145DE8B232C68F9B452625.taxon	description	Description. Shell medium-sized (shell length 43.3 – 61.4 mm, shell height 24.5 – 35.1 mm, shell width 13.4 – 18.4 mm; Table 2), rhomboidal, elongate (H / L ratio = 0.55 – 0.57), rather thin, very inequilateral, moderately inflated. Anterior margin rounded, rather constricted, shouldered; posterior margin truncated, slightly elongate ventrally; ventral margin slightly curved. Dorsal margin slightly curved; anterior low, posterior end slightly higher. Umbo slightly elevated, heavily eroded even in young specimens. Posterior ridge wide and obtuse, not prominent; posterior slope with two faint lines running from umbo to posterior margin. Periostracum thin, brownish-black, eroded part white to coppery-brown. Shell surface with visible growth lines. Ligament long, very narrow, dark brown. One very shallow hill-like or triangulate pseudocardinal tooth on right valve; pseudocardinal tooth on left valve less developed, tubercule-like, or almost absent. Posterior end of hinge structure with small V-shaped fossette. Anterior adductor muscle scar shallow, ovate, contiguous with pedal retractor and anterior protractor muscle scars; posterior adductor muscle scar round, very shallow, almost invisible. Pallial line faint, continuous. Umbo cavity moderately deep, with 1 to 2 tiny muscle scars in the cavity. Nacre blue-whitish with yellowish tint around the umbo cavity. Exhalant aperture almost smooth, with a row of tiny tubercle-like papillae on edge of aperture, shorter than inhalant. Inhalant aperture with a row of conical papillae, varying in length. Small epithelial fold divides exhalant and inhalant apertures. Gills elongated and slightly ribbed; inner gills slightly wider, and anterior margin of inner gills slightly longer than that of outer gills. Labial palps elongate, slightly curved, pointed at tip. Glochidia unknown.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
B4A368D346145DE8B232C68F9B452625.taxon	etymology	Etymology. The species name “ fortunata ” is derived from the Latin adjective “ fortunatus ” meaning lucky. This name refers to the fortuitous discovery of this rare freshwater species.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
B4A368D346145DE8B232C68F9B452625.taxon	distribution	Distribution. This new species is known only from the type locality.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
C0910C0350AE55BFB0CF0786B4F04852.taxon	type_taxon	Type species. Isannaia fortunata gen. et sp. nov., by present designation.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
C0910C0350AE55BFB0CF0786B4F04852.taxon	diagnosis	Diagnosis. The new genus is distinguished from other genera in the Pseudodontini by its thin and moderately inflated shell, and with rhomboidal to ovate outline (Fig. 4). The overall shape is somewhat elongated but relatively shorter when compared to those of Bineurus, Pilsbryoconcha or Namkongnaia. The anterior margin is rounded, shouldered, and the posterior margin is truncated to rounded. Its pseudocardinal teeth are rather small, one on each valve, hill-like or triangulate shape, and less developed on the left valve. Its umbo is slightly elevated and the umbo cavity moderately deep. It is also represented as a distinct clade in multi-locus phylogenetic analyses (Fig. 1).	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
C0910C0350AE55BFB0CF0786B4F04852.taxon	description	Description. Shell medium-sized, rather thin, rhomboidal to ovate outline, elongate, very inequilateral, moderately inflated; anterior margin rounded, shouldered; posterior margin truncated to rounded. Umbo slightly elevated and usually eroded. Ligament very narrow. One shallow hill-like or triangulate pseudocardinal tooth on right valve; left valve with one less developed hill-like to tubercule-like pseudocardinal tooth. End of hinge structure with V-shaped fossette. Anterior adductor muscle scar shallow to well-developed, ovate, contiguous with pedal retractor and anterior protractor muscle scars; posterior adductor muscle scar round, very shallow. Pallial line faint to well-marked, continuous. Umbo cavity moderately deep.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
C0910C0350AE55BFB0CF0786B4F04852.taxon	etymology	Etymology. The generic name “ Isannaia ” is from the word “ Isan ”, the name of the region of northeastern Thailand, and Greek word “ naiad ” meaning freshwater mussel. The name of this genus thus means “ freshwater mussels from northeastern Thailand ”. The gender is feminine.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
C0910C0350AE55BFB0CF0786B4F04852.taxon	distribution	Distribution. Endemic to tributaries of the Mekong River in northeastern Thailand (Fig. 3).	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
ACBEF56237745895AE444C49C4EE638E.taxon	description	Figs 1, 3, 4 C, D	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
ACBEF56237745895AE444C49C4EE638E.taxon	diagnosis	Diagnosis. This species resembles I. fortunata sp. nov., but it can be distinguished by the overall shell shape being more rounded (vs rhomboidal), slightly higher shell (H / L ratio 0.58 – 0.60 vs 0.55 – 0.57), wider anterior margin (vs rather constricted), more truncated and rounded posterior margin (vs slightly ventrally elongate), less curved ventral margin (vs curved ventral margin). It also differs in characteristics inside the shell by having higher and more triangulate pseudocardinal tooth on the right valve (vs very shallow and hill-like pseudocardinal tooth), well-developed muscle scars (vs very shallow and sometimes almost invisible), 3 to 5 well-developed muscle scars in the umbo cavity (vs 1 to 2 tiny muscle scars in the umbo cavity), and well-marked pallial line (vs faint pallial line). It can also be distinguished from its congeners by fixed nucleotide substitution positions in the COI gene fragment of base A on the 54 th, 114 th, 363 rd, and 414 th; base T on the 90 th, 141 st, 591 st, and 609 th; base C on the 57 th, and 216 th; and base G on 150 th, 117 th, 192 nd, 558 th, 480 th, 552 nd, 627 th, 639 th, 645 th, and 657 th.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
ACBEF56237745895AE444C49C4EE638E.taxon	description	Description. Shell medium-sized (shell length 43.8 – 53.8 mm, shell height 26.7 – 31.7 mm, shell width 13.8 – 20.4 mm; Table 2), ovate to rectangular, elongate (H / L ratio = 0.58 – 0.60), rather thin, very inequilateral, moderately inflated. Anterior margin rounded, shouldered; posterior margin truncated to rounded; ventral margin straight to slightly curved. Dorsal margin slightly curved; anterior low, posterior end slightly higher. Umbo slightly elevated, heavily eroded even in young specimens. Posterior ridge wide and obtuse, not prominent; posterior slope with two faint lines running from umbo to posterior margin, invisible in old specimens. Periostracum thin, brown to brownish-black, eroded part white to coppery-brown. Shell surface with visible growth lines. Ligament long, very narrow, dark brown. One hill-like or triangulate pseudocardinal tooth on right valve; pseudocardinal tooth on left valve less developed, hill-like. Posterior end of hinge structure with small V-shaped fossette. Anterior adductor muscle scar well-developed, ovate, contiguous with anterior pedal retractor and anterior protractor muscle scars; posterior adductor muscle scar round, shallow, contiguous with posterior retractor muscle scars; posterior retractor muscle scars triangular. Pallial line well-marked, continuous. Umbo cavity moderately deep, with 3 to 5 muscle scars in cavity. Nacre blue-whitish to yellowish, more yellowish toward the umbo cavity. Exhalant aperture almost smooth, with a row of tiny tubercle-like papillae on the edge of aperture, similar length with inhalant. Inhalant aperture with a row of very short conical papillae. Small epithelial fold divides exhalant and inhalant apertures. Gills elongated and slightly ribbed; inner gills slightly wider, and anterior margin of inner gills slightly longer than that of outer gills. Labial palps elongate, slightly curved, pointed at tip. Glochidia unknown.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
ACBEF56237745895AE444C49C4EE638E.taxon	etymology	Etymology. The species name “ occultata ” is derived from the Latin adjective “ occultatus ” meaning concealed or hidden, a reference to this new freshwater mussel being hidden in a small stream far from the main river.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
ACBEF56237745895AE444C49C4EE638E.taxon	distribution	Distribution. This new species is known only from the type locality, Yang Stream in Udon Thani Province. Yang Stream is a headwater tributary of the Lam Pao River in the Chi River Basin. The type locality is above the Lam Pao Dam.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
37E406E32C2254DF9F22C25E8BA1B68F.taxon	type_taxon	Type species. Lannanaia kokensis gen. et sp. nov., by present designation.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
37E406E32C2254DF9F22C25E8BA1B68F.taxon	diagnosis	Diagnosis. This new genus is distinguished from other Pseudodontini genera by its compressed, rather short and high shell, with sub-trigonal outline, and distinct posterior wing. The hinge plate is without dentition, or with very rudimentary broad pseudocardinal tooth in each valve, and posterior end of the hinge structure with rather wide V-shaped fossette (Fig. 2). It is also represented as a distinct clade in multi-locus phylogenetic analyses (Fig. 1).	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
37E406E32C2254DF9F22C25E8BA1B68F.taxon	description	Description. Shell medium-sized, thin, rather short and high, winged, sub-trigonal outline, inequilateral, rather compressed. Anterior margin rounded; posterior margin angulate, somewhat pointed. Umbo tiny, not prominent, eroded. Ligament long, very narrow. Hinge without dentition, or with very rudimentary broad pseudocardinal tooth in each valve; posterior end of the hinge structure with rather wide V-shaped fossette. Anterior adductor muscle scar very shallow, ovate, contiguous with anterior pedal retractor muscle scar, but separated from anterior protractor scar; posterior adductor muscle scar round, very shallow, almost invisible. Pallial line very faint, continuous. Umbo cavity shallow.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
37E406E32C2254DF9F22C25E8BA1B68F.taxon	etymology	Etymology. The generic name “ Lannanaia ” is from the word “ Lanna ”, a name of the kingdom located in present-day northern Thailand during the 13 th to 18 th centuries, and the Greek word “ naiad ” meaning freshwater mussel. The name of this genus thus means “ freshwater mussels from Lanna ” or “ freshwater mussels from northern Thailand ”. The gender is feminine.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
37E406E32C2254DF9F22C25E8BA1B68F.taxon	distribution	Distribution. Endemic to Kok River, a tributary of the Mekong River in northern Thailand (Fig. 3).	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
6A0BC990AA2155A9A787499DACD59067.taxon	description	Figs 1, 2, 3	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
6A0BC990AA2155A9A787499DACD59067.taxon	description	Description. Shell medium-sized (shell length 57.1 – 57.2 mm, shell height 40.8 – 43.8 mm, shell width 14.4 – 14.8 mm; Table 2), thin, rather short and high (H / L ratio = 0.71 – 0.77), winged, sub-trigonal outline, inequilateral, rather compressed. Anterior margin rounded; posterior margin angulate, somewhat pointed; ventral margin curved. Dorsal margin straight; anterior low and short, gradually elevated to posterior end; posterior end high and winged. Umbo tiny, not prominent, eroded. Posterior ridge wide and obtuse, not prominent; posterior slope with two fine lines running as curved line from umbo to posterior margin. Periostracum thin, greenish to dark brown, the eroded part white to coppery-brown. Shell surface with very fine growth lines. Ligament long, very narrow, dark brown. Hinge without dentition, or with very rudimentary broad pseudocardinal tooth in each valve; posterior end of hinge structure with rather broad V-shaped fossette. Anterior adductor muscle scar very shallow, ovate, contiguous with anterior pedal retractor muscle scar, but separated from anterior protractor scar; posterior adductor muscle scar round, very shallow, almost invisible. Pallial line very faint, continuous. Umbo cavity shallow. Nacre blue-whitish. Exhalant aperture smooth, shorter than inhalant. Inhalant aperture with a row of conical papillae, varying in length. Small epithelial fold divides exhalant and inhalant apertures. Gills elongated and slightly ribbed; outer gills much narrower (about half) than inner gills; anterior margin of inner gills slightly longer than that of outer gills. Labial palps elongate, round at tip. Glochidia unknown.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
6A0BC990AA2155A9A787499DACD59067.taxon	etymology	Etymology. The species name “ kokensis ” refers to the type locality, the Kok River in Chiang Rai Province, northern Thailand.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
6A0BC990AA2155A9A787499DACD59067.taxon	distribution	Distribution. This new species is known only from the type locality.	en	Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Prasankok, Pongpun (2024): Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution 100 (4): 1333-1345, DOI: 10.3897/zse.100.130929
