taxonID	type	description	language	source
03969976961CFFB3FE9AF9EE794CAB12.taxon	type_taxon	Type species. Neostethus lankesteri Regan, 1916 by original designation (use of “ gen. et sp. n. ” for one of two included new species).	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
03969976961CFFB3FE9AF9EE794CAB12.taxon	diagnosis	Differential diagnosis. (modified from Parenti, 1989: 269) Neostethus differs from all other phallostethines in having a priapium with an inner pulvinular bone (vs. lacking the bone), thin bony projections on the papillary bone that may number 80 or more (vs. lacking such bony projections) (Parenti, 1989: fig. 3) and two ctenactinia (vs. just a single short or rudimentary second (and no first) ctenactinium in Phallostethus and Phenacostethus and one elongate first (and no second) ctenactinium in Gulaphallus). Males lack an enlarged, fleshy seminal papilla and there is no translucent, membranous dome on the dorsal surface of the head as in Phallostethus and Phenacostethus. Males also do not have a perforated gular flap of skin through which the anterior end of the first ctenactinium projects or an aproctal axial bone that projects beyond the ventral body profile (Parenti, 1989: fig. 4) which diagnoses Gulaphallus. Composition. Twelve species, including the new species described herein (Table 1).	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
03969976961CFFB7FC12FD0E79A0A8F1.taxon	description	(Figs. 1, 2 A, 3 A, 4 C, 5 A, 6 A, 7)	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
03969976961CFFB7FC12FD0E79A0A8F1.taxon	materials_examined	Material examined. All specimens collected in Brunei Darussalam. Holotype: USNM 409956 (sinistral male, 23.3 mm SL), Tutong Dist., Sg. Birau, trib. of Sg. Tutong, just above where it enters Sg. Tutong, E of Bandar Tutong, 4 ° 48 ' 0 " N, 114 ° 40 ' 38 " E, coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bahrin, Abu Bakar & Bujong, 25 August 1997. Paratypes: Brunei Museum / USNM 409980 (40, 10 sinistral males, 10 dextral males, 10 females, 10 imm., 16.8 – 23.0 mm SL), USNM 409963, (95, 14 sinistral males, 12 dextral males, 27 females, 42 imm., 11.3 – 25.7 mm SL, of which one sinistral male, one adult female and one imm. male were cleared and stained solely with alcian blue and one sinistral male was cleared and stained solely with alizarin), BMNH 2013.5.10.2 - 4, sinistral male, 23.8 mm SL, dextral male, 23.5 mm SL, female, 18.8 mm SL; CAS 235597, sinistral male, 23.7 mm SL, dextral male, 23.0 mm SL, female, 19.5 mm SL; FMNH 121800, sinistral male, 23.4 mm SL, dextral male, 23.8 mm SL, female, 19.8 mm SL; MCZ 170559, sinistral male, 22.4 mm SL, dextral male, 24.5 mm SL, female, 18.3 mm SL; ZRC 54117, sinistral male, 23.8 mm SL, dextral male, 24.5 mm SL, female, 18.8 mm SL, all collected with the holotype. USNM 409957 (133, 17 sinistral males, 15 dextral males, 25 females, 76 imm., 12.5 – 24.8 mm SL, of which one dextral male, one sinistral male, and two adult females were cleared and counterstained), Belait District, Sg. Dalit, just above where it enters Sg. Belait, 4 ° 34 ' 0 " N, 114 ° 12 ′ 0 ″ E, coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bakana, Hj. Bahrin, M. Wong & Yussof, 27 August 1997; USNM 356847 (10, 13 – 24 mm SL), Tutong Dist., Sg. Tutong, upstream from Bandar Tutong near Kampung Panchor Dulif, 4 ° 46 ' 04 " N, 114 ° 36 ' 12 " E, coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Zainal & Hj Ariffin, 23 August 1997; USNM 409958 (10, 9 – 24.8 mm SL), Belait Dist., Sg. Teraban, trib. of Sg. Belait, just above where it enters main river channel, and in main channel, 4 ° 34 ' 41 " N, 114 ° 10 ' 59 " E, coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bahrin & Yussof, 26 – 27 August 1997; USNM 409960 (adult female, 19 mm SL), Tutong Dist., Sg, Gandang, trib. of Sg. Penyatang, coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bakana, Hj. Bahrin, Abu Bakar & Hj. Ariffin, 24 August 1997; USNM 365135 (47, 10 – 20.5 mm SL), Belait Dist., Sg. Limatak, just above where it enters Sg. Belait, 4 ° 34 ' 20 " N, 114 ° 11 ' 33 " E, coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bakana, Hj. Bahrin, M. Wong & Yussof, 27 August 1997. Nontype specimens (all poorly preserved or distorted): USNM 409959 (90, 7 – 24 mm SL), from the type locality; USNM 389677 (4, alcohol fixed), USNM 389674 (2, alcohol fixed), Belait District, Sg. Dalit, just above where it enters Family Phallostethidae Subfamily Denatherininae Genus Dentatherina Patten & Ivantsoff 1983 Denatherina merceri Patten & Ivantsoff 1983 Subfamily Phallostethinae Tribe Phallostethini Genus Phallostethus Regan, 1913 Phallostethus dunckeri Regan, 1913 Phallostethus lehi Parenti, 1996 * Phallostethus cuulong Shibukawa et al., 2012 Genus Phenacostethus Myers, 1928 Phenacostethus smithi Myers, 1928 * Phenacostethus posthon Roberts, 1971 a Phenacostethus trewavasae Parenti, 1986 * Tribe Neostethini Genus Neostethus Regan, 1916 Neostethus lankesteri Regan, 1916 * Neostethus bicornis Regan, 1916 * Neostethus amaricola (Villadolid & Manacop, 1935) Neostethus palawanensis (Myers, 1935) Neostethus thessa (Aurich, 1937) Neostethus ctenophorus (Aurich, 1937) Neostethus borneensis Herre, 1939 * Neostethus villadolidi Herre, 1942 Neostethus zamboangae Herre, 1942 Neostethus robertsi Parenti, 1989 Neostethus djajaorum Parenti & Louie, 1998 Neostethus geminus, new species * Tribe Gulaphallini Genus Gulaphallus Herre, 1925 Gulaphallus eximius Herre, 1925 Gulaphallus mirabilis Herre, 1925 Gulaphallus falcifer Manacop, 1936 Gulaphallus bikolanus (Herre, 1926) Gulaphallus panayensis (Herre, 1942) Sg. Belait, 4 ° 34 ' 0 " N, 114 ° 12 ' 0 " E, coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bakana, Hj. Bahrin, M. Wong & Yussof, 27 August 1997.	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
03969976961CFFB7FC12FD0E79A0A8F1.taxon	diagnosis	Differential diagnosis. Neostethus geminus and N. bicornis are distinguished from all other phallostethid fishes by mature males with two elongate ctenactinia (vs. one elongate and one short ctenactinium in other Neostethus), immature males with a brown blotch on the pelvic fin rays of the proctal side, which fades with growth and maturity, and females with a fleshy, hoodlike fold or flap that includes the anus, genital pore and urinary pore. These characters were considered diagnostic of N. bicornis by Parenti (1989). Neostethus geminus differs from N. bicornis in being smaller (reaching no more than 25.7 mm SL vs. 31 mm SL) and having a relatively compact priapium with a foreshortened, broad aproctal axial bone that meets but does not overlap the pulvinular appendage (vs. a relatively elongate priapium with a long and narrow aproctal axial bone that overlaps the pulvinular appendage medially; Figs. 3, 4), thin, nearly translucent, broad papillary bone expanded distally into a tab (vs. a short papillary bone; Figs. 3,4), and females with a thickened fleshy, hoodlike fold that includes the anus, genital pore and urinary pore (vs. a thin fold of skin; Fig. 6), and a thickened ridge just posterior to the fold and separated from it by a gap (vs. lacking a ridge and a gap; Fig. 6).	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
03969976961CFFB7FC12FD0E79A0A8F1.taxon	description	Description. Meristic data for the new species are summarised in Table 2. A small, laterally compressed species, maximum size recorded 25.7 mm SL. No vestigial pelvic-fin rays or bones in adult females; males with parts of pelvic and pectoral fins modified into priapium that is either sinistral (holotype, 46 male paratypes) or dextral (42 male paratypes). Two prominent externalised subcephalic bones: an elongate first ctenactinium arises on either left or right side of body and articulates with posterior extent of left or right (proctal) axial bone, curves gently along the left or right side of the head and the somewhat expanded tip lies just ventral to the lower jaw (Figs. 2 A, 3 A). A curved second ctenactinium about one-half the length of the first arises on the same side of the body and articulates with the posterior extent of left or right (proctal) axial bone (Figs. 3 A, 4 C) reaches the fibrous, oval pulvinulus which is lateral to, and covers articulation point of, inner pulvinular and proctal axial bones. Papillary bone with numerous thin, bony segments, confluent posteriorly to form a broad, elongate, translucent tab with faint striations. Aproctal axial bone short and broad, meets posterior extent of pulvinular appendage (Figs. 3 A, 4 C). Immature males with a small pelvic fin or fins on the proctal side of the body. Mature males with two small bundles of rudimentary pelvicfin rays in the wall of the membranous sac at the posterior extent of the priapium. Pleural ribs of fourth vertebra in males expanded anteroposteriorly, their distal tips meet on right side of proctal axial bone in sinistral males and left side in dextral males; parapophysis on right side greatly expanded and oriented anteriorly in sinistral males, on left side in dextral males. First pleural rib on third vertebra in females. Females with a thickened fleshy, hoodlike fold that includes the anus, genital pore and urinary pore and a thickened ridge just posterior to the fold (Fig. 6 A). Ventral dermal keel extends from body just posterior to thickened ridge in females or constricted body just posterior to the priapium in males, to just before the anal-fin origin (Fig. 5). Swim bladder spans four to five body segments anterior to anal-fin base. Neurocranium and jaws like those illustrated for Neostethus bicornis by Roberts (1971 b), with little modification. Posttemporal bone forked, lower limb short and connected via a ligament to the basicranium. Jaw teeth conical, in a single uneven row, small medially and progressively larger distally. Paradentary bone edentulous. Caudal fin forked. Caudal skeleton with two thin epurals, autogenous parhypural, and a dorsal and a ventral hypural plate. Principal caudal-fin rays i, 7 – 8 / 7 – 8, i [i, 7 / 7, i]. Pectoral fin narrow and elongate, with 10 – 11 [11] rays. Two dorsal fins, the first with one short, thickened ray followed by a thinner second ray in males, both supported by a single, elongate pterygiophore; the second fin with 6 – 7 [7] rays, the second through fourth or fifth branched, the first and last articulated, but not branched. Anal-fin rays 15 – 16 [15], the first ray short and unsegmented. Vertebrae 35 – 37 [37] (precaudal 16 – 18 + caudal 19 – 20, including half centrum). Branchiostegal rays 5. Scales on body of moderate size, deciduous, 34 – 36 [34] in a transverse series. Colour in life. Body largely translucent with melanophore pigmentation pattern as in preservative, below. Specimens from the type locality at capture had a bright orange blotch on the caudal peduncle and a bright orange band at midbody, just anterior to the anal fin (see Remarks, below). Colour in preservative. Preserved, formalin-fixed, specimens (Figs. 2, 5) with ground colour pale yellow. Dark brown melanophores scattered on dorsal surface of head, just ventral to the midline, on operculum and priapium, along basal portion of anal fin, pectoral fin, dorsal and ventral midline, and abdomen where they are concentrated into a blotch in some specimens. An arc of small brown melanophores on the posteroventral rim of the orbit. All fin rays with thin, black, interrupted to complete line of melanophores on margin. A discrete, thin black line along midlateral, intermuscular septum from pectoral fin to caudal fin base. Dorsal and ventral extent of hypural plates with indistinct black blotch. Body scales with a posterior margin of small brown melanophores. Immature males with a brown blotch on the pelvic-fin rays of the proctal side and a line of brown melanophores on the ventral surface of the body from about the position of the first through third pleural rib. Medial portions of membranous sac at the posterior extent of the priapium in mature males dark brown.	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
03969976961CFFB7FC12FD0E79A0A8F1.taxon	distribution	Distribution and habitat. Neostethus geminus was collected from six localities in the Belait and Tutong districts of Brunei, clustered near Kuala Belait and Kuala Tutong (Fig. 7). At the type locality, N. geminus was collected using dip nets and a scoop net along with other fish species representative of a Southeast Asian nipah forest biota including Ambassis sp., Scatophagus argus, Tetraodon leiurus, Gobiopterus brachypterus, and Brachygobius doriae; a mangrove colubrid snake, Cerberus sp., was also seen. Neostethus borneensis was the only other phallostethid species collected with N. geminus. The brackish water was clear and brown with a temperature of 27 ° C.	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
03969976961CFFB7FC12FD0E79A0A8F1.taxon	etymology	Etymology. geminus, Latin for twin or double referring to the close morphological similarity of the new species to its inferred sister species, N. bicornis, and to the paired or double ctenactinia in both species.	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
03969976961CFFB7FC12FD0E79A0A8F1.taxon	discussion	Remarks. Collections examined here of both N. bicornis and N. geminus contain roughly even numbers of sinistral and dextral males that, together, number somewhat more than the total number of females (see Material Examined). A bright orange blotch on the caudal peduncle in freshly caught specimens of Phallostethus cuulong was illustrated by Shibukawa et al. (2012: fig. 1). Bright orange-yellow markings on the caudal peduncle and, rarely, at the base of the anal fin were reported by Roberts (1971 a) for Phenacostethus posthon and P. smithi; he noted that such markings were unknown in Neostethus. There are few photographs of live or freshly caught Neostethus; a freshly-caught dextral male N. bicornis from Singapore has orange-yellow blotches at the base of the caudal-fin rays (see below). Other atherinomorph fishes may have orange markings on the caudal fin; the North American Desert Pupfish, Cyprinodon macularius has a lemon yellow to orange caudal peduncle (Page & Burr, 2011). These markings fade rapidly upon formalin-fixation and preservation in alcohol. The distribution of the caudal peduncle and mid-body orange markings in atherinomorphs is unknown and, therefore, I do not include the markings as diagnostic of the new species.	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
039699769618FFB8FC14FE2D7CBEACD0.taxon	description	(Figs. 1, 2 B, 3 B, 4 A, B, 5 B, 6 B, 8)	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
039699769618FFB8FC14FE2D7CBEACD0.taxon	diagnosis	Differential diagnosis. Neostethus bicornis and N. geminus are distinguished from all other phallostethid fishes by mature males with two elongate ctenactinia (vs. one elongate and one short ctenactinium as in other Neostethus), immature males with a brown blotch on the pelvic-fin rays of the proctal side which fades with growth and maturity, and females with a fleshy, hoodlike fold that includes the anus, genital pore and urinary pore. I (Parenti, 1989) considered these characters diagnostic of N. bicornis which differs from the new species, N. geminus, in being larger (reaching 31 mm SL vs. no more than 25.7 mm SL), having a priapium with a relatively long and narrow aproctal axial bone that overlaps the pulvinular appendage medially (vs. relatively compact priapium with a foreshortened, broad aproctal axial bone that meets but does not overlap the pulvinular appendage; Figs. 3, 4), a short, translucent papillary bone (vs. a thin, nearly translucent, broad papillary bone expanded distally into a tab; Figs. 3, 4), and females with a thin fleshy, hoodlike fold that includes the anus, genital pore and urinary pore (vs. a thick fold; Fig. 6), and no thickened ridge just posterior to the fold (vs. having a ridge; Fig. 6).	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
039699769618FFB8FC14FE2D7CBEACD0.taxon	description	Description. A small, laterally compressed species, maximum size recorded 31 mm SL. No vestigial pelvic fin rays or bones in adult females; males with parts of pelvic and pectoral fins modified into priapium that is either sinistral or dextral. Two prominent externalised subcephalic bones: an elongate first ctenactinium arises on either left or right side of body and articulates with posterior extent of left or right (proctal) axial bone, curves gently along the left or right side of the head and the somewhat expanded tip lies just ventral to the lower jaw (Figs. 2 B, 3 B). A curved second ctenactinium about one-half the length of the first arises on the same side of the body and articulates with the posterior extent of left or right (proctal) axial bone (Figs. 3 B, 4 A, B) reaches the fibrous, oval pulvinulus which is lateral to, and covers articulation point of, inner pulvinular and proctal axial bones. Papillary bone with numerous thin, bony segments, confluent posteriorly, not forming an elongate tab. Aproctal axial bone long and narrow, overlaps the pulvinular appendage medially. Immature males with a small pelvic fin or fins on the proctal side of the body. Mature males with two small bundles of rudimentary pelvic-fin rays in the wall of the membranous sac at the posterior extent of the priapium. Pleural ribs of fourth vertebra in males expanded anteroposteriorly, their distal tips meet on right side of proctal axial bone in sinistral males and left side in dextral males; parapophysis on right side greatly expanded and oriented anteriorly in sinistral males, on left side in dextral males. First pleural rib on third vertebra in females. Females with a thin fleshy, hoodlike fold that includes the anus, genital pore and urinary pore and no thickened ridge just posterior to the fold (Fig. 6 B). Ventral dermal keel extends from body just posterior to thickened ridge in females or constricted body just posterior to the priapium in males, to just before the anal-fin origin (Fig. 5). Neurocranium and jaws as illustrated by Roberts (1971 b). Post-temporal bone forked, lower limb short and connected via a ligament to the basicranium. Jaw teeth conical, in a single uneven row, smaller medially and progressively larger distally. Paradentary bone edentulous. Caudal fin forked. Caudal skeleton with two thin epurals, autogenous parhypural, and a dorsal and a ventral hypural plate. Principal caudal-fin rays i, 7 – 8 / 7 – 8, i. Pectoral fin narrow and elongate, with 10 – 11 rays. Two dorsal fins, the first with one short, thickened ray followed by a thinner second ray in most adult males and females, both supported by a single, elongate pterygiophore; the second fin with 5 – 6 rays, the second through fourth or fifth branched, the first and last articulated, but not branched. Anal-fin rays 13 – 16, the first ray short and unsegmented. Vertebrae 36 – 37 (precaudal 17 – 18 + caudal 18 – 20, including half centrum). Branchiostegal rays 5 – 6. Scales on body of moderate size, deciduous, 31 – 37 in a transverse series. Colour in life. Body and fins nearly transparent in life. Other pigmentation as in alcohol specimens described below. A fresh specimen of a dextral male captured during the October 2012 Straits of Johore Biodiversity Survey, Singapore, photographed by Arthur Anker (http: // www. flickr. com / photos / artour _ a / 8147112311; Accessed 12 December 2013) has yellow blotches at the base of the caudal-fin rays. Dark brown melanophores that line the dorsal portion of the body cavity and anterior portion of the testis and gut are also visible. The reddish colour of the gills in this specimen is an exaggeration, the result of its being placed on ice. Colour in preservative. Preserved, formalin-fixed specimens with ground colour pale yellow, brownish in specimens from Sabah. Dark brown melanophores scattered on dorsal surface of head, just ventral to the midline, on operculum and priapium, along basal portion of anal fin, pectoral fin, dorsal and ventral midline, and abdomen where they are concentrated into a blotch in some specimens. An arc of small brown melanophores on the posteroventral rim of the orbit. All fin rays with thin, black, interrupted to complete line of melanophores on margin. A discrete, thin black line along midlateral, intermuscular septum from pectoral fin to caudal fin base. Dorsal and ventral extent of hypural plates with indistinct black blotch. Body scales with a posterior margin of small brown melanophores. Immature males with a brown blotch on the pelvic-fin rays of the proctal side and a line of brown melanophores on the ventral surface of the body from about the position of the first through third pleural rib. Medial portions of membranous sac at the posterior extent of the priapium in mature males medium to dark brown.	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
039699769618FFB8FC14FE2D7CBEACD0.taxon	distribution	Distribution and habitat. Widespread in coastal, brackish water habitats from Thailand, Peninsula Malaysia, Singapore, East Malaysia (Sarawak and Sabah), Kalimantan, Indonesia (see Parenti & Louie, 1998), Brunei, and Palawan Is., Philippines (Fig. 1).	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
039699769618FFB8FC14FE2D7CBEACD0.taxon	materials_examined	Material examined. Peninsula Malaysia: Lectotype: BMNH 1937.2.9: 4 (imm. dextral male, 20.9 mm SL), designated by Parenti (1989); Paralectotypes: BMNH 1937.12.9: 5 – 6 (female, 16.7 mm SL; imm. male, 19.1 mm SL), Kuala Langat, Selangor, coll. G. Duncker. Thailand: Central Thailand: brackish fish farming ponds in area of Samut Sakhon, ca. 25 km S of the center of Bangkok, USNM 358614 (5, 20 – 23.5 mm SL), coll. A. Whitehouse, 1 December 1997. Chanthaburi: ca. 1 / 2 km up from mouth of Chantiburi R. (near Tah Chalap), MCZ 47306 (adult sinistral male, CT micrograph), coll. T. R. Roberts & P. Wongrat, 5 May 1970. Chumporn Prov., Klong Panangtak in vicinity of Banthup Tanhot ca. 5 km from Chumporn town, CAS 63196 (2, sinistral male, sinistral female, 22 mm SL), coll. H. A. Fehlmann, 22 May 1960. Singapore: CAS-SU 31133 (10, 3 sinistral males, 7 dextral males, 26 – 28 mm SL), coll. A. W. C. T. Herre, 1934. USNM 102142 (8, sinistral male, 4 dextral males, 3 females; 21.0 – 28.0 mm SL), coll. A. W. C. T. Herre, 18 March 1934. Kranji R., CAS-SU 35783 (52, 13 sinistral males, 9 dextral males, 27 females, 3 imm., 15 – 28 mm SL, of which 2 sinistral male, 2 dextral male and 6 females have been cleared and stained solely with alizarin), coll. A. W. C. T. Herre, March 1937. Seletar R., CAS-SU 67161 (10, 2 sinistral males, 6 dextral males, 1 female, 1 imm, 18.1 – 27.8 mm SL), coll. E. Alfred, 11 February 1966. Sg. Buloh just outside of nature reserve, small stream entering Straits of Johore, USNM 348392 (50 +, sinistral male, dextral male, female cleared and stained solely with alizarin), USNM 373890 (4 pres. in ethanol), coll. L. R. Parenti, H. K. Larson, K. Lim & N. Sivasothi, 5 September 1997. East Malaysia, Sarawak: Kuching, Sarawak R., N. bank at Kampung Tupung, USNM 325053 (30, imm. 5 – 16.5 mm SL). Brunei: Tutong Dist.: Kuala Tutong at Tg. Tanah Palang, USNM 409961 (45, 9 sinistral males, 10 dextral males, 14 adult females, 9 imm., from which one dextral male and one female were cleared and stained solely with alcian blue and one dextral male was cleared and stained solely with alizarin; 12 – 29 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bahrain, Abu Bakar & Zainal, 23 August 1997. Kuala Tutong, small stream that enters main river (4 ° 47 ' 09 " N, 114 ° 36 ' 56 " E), USNM 409964 (317, of which one sinistral male, one dextral male, and 2 adult females were cleared and counterstained), coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bahrin, Abu Bakar & Bujang, 25 August 1997. Lubok api-api, Kuala Tutong (4 ° 45 ' 12 " N, 114 ° 35 ' 18 " E), USNM 356849 (50 +, 10 – 25 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bahrin, Abu Bakar, & Hj. Ariffin, 24 August 1997. Sg. Penabai, trib. of Sg. Tutong where it enters Sg. Tutong (4 ° 46 ' 29 " N, 114 ° 36 ' 16 " E), USNM 356846 (50 +, 12 – 29.5 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bahrain, Abu Bakar & Zainal, 23 August 1997. Temburong Dist.: Sg. Mataiang on Hutan Simpan Selirong at Forest Dept. jetty, (4 ° 53 ' 26 " N, 115 ° 07 ' 06 " E), USNM 364887 (30, 7 – 28.5 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Ahmad & Pinde, 30 August 1997. Sg. Raya, Trib. of Sg. Temburong (4 ° 48 ' 11 " N, 115 ° 03 ' 47 " E), USNM 409934 (8, 8.5 – 28.7 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bakaria, Hassan & Pinde, 21 August 1997. Pulau Pitu at sg. that enters Sg. Temburong just downstream from confluence with Sg. Labu (4 ° 45 ' 57 " N, 115 ° 04 ' 44 " E), USNM 365125 (2, 13.5 – 14.5 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Bakaria, Hassan & Pinde, 21 August 1997. Brunei- Muara Dist.: Sg. Kalmasi, trib. of Sg. Brunei, (4 ° 50 ' 44 " N, 114 ° 57 ' 18 " E), USNM 378045 (21, 11.2 – 28.6 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ahmad & Hj. Junggal, 16 August 1997. Sg. Pulau Berambang, Tg. Bakaka, shore and stream that enters Brunei Bay, (4 ° 54 ' 04 " N, 115 ° 01 ' 25 " E), USNM 356128 (27, 10 – 28.2 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ramlee, Hj. Ahmad & Pinde. 30 August 1997. Sg. Mambangan, trib. of Sg. Brunei, from above to where it enters Sg. Brunei, opposite Kampung Dato Gandi, USNM 356848 (61, 8 – 28. 6 mm SL), USNM 389678 (5 pres. in ethanol), coll. L. R. Parenti, H. K. Larson, Hj. Ahmad & Hj. Junggal, 15 August 1997. Sg. Dolhakim, trib. stream of Sg. Brunei, USNM 364888 (17, 9.5 – 27.5 mm SL), coll. L. R. Parenti, H. K. Larson, Hj. Ahmad & Hj. Junggal, 17 August 1997. Main wharf [Bandar Seri Begawan], CAS- SU 61764 (dextral male, 24 mm SL), coll. J. A. Tubb, 30 July 1948. East Malaysia, Sabah: East Coast Residency, Kinabatangan Dist., Little Kretam R., winding embayment into nipah swamp, mouth of Ayer Terjun, FMNH 51726 (87, 8 dextral males, 7 sinistral males, 53 adult females, 29 imm., 8.5 – 26 mm SL), coll. R. F. Inger, 10 May 1950; near mouth of Kretam Kechil R., FMNH 51727 (6, dextral male, 2 sinistral males, 3 adult females, 20 – 24.5 mm SL), coll. R. F, Inger, 25 May 1950; fork of East and West Gaja, in West Fork, 100 yds.; trib. of Kretam Kechil R., FMNH 51728 (41, 10 dextral males, 15 sinistral males, 14 adult females, 2 imm., 15.5 – 25 mm SL), coll. R. F. Inger, 22 May 1950; mouth of Pinang R. (trib. of Little Kretam R.), FMNH 51729 (26, 8 dextral males, 10 sinistral males, 6 adult females, 2 imm., 10 – 27 mm SL), coll. R. F. Inger, 10 June 1950. Philippines: Palawan, Nakoda Bay, USNM 98838 (3, sinistral male, 2 adult females, 26 – 29 mm SL), USNM 98839 (3, sinistral male, 2 adult females, 27 – 31 mm SL), unnamed river SE of Maricaban Is., USNM 150632 (2, dextral male, sinistral male, 30.0 mm SL), coll. Albatross, 31 December 1908; Malampaya Sound, Malampaya R., USNM 98840 (1 sinistral male, 30.0 mm SL), coll. Albatross, 26 December 1908.	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
039699769618FFB8FC14FE2D7CBEACD0.taxon	discussion	Remarks. Although Regan (1916) did not report first dorsalfin rays in his description of N. bicornis, a single first dorsalfin ray was found subsequently in his type material (Myers, 1937: 141). All specimens examined here have at least one thickened first dorsal-fin ray. The small, second dorsal-fin ray is absent in female N. geminus and some females and males of N. bicornis examined here. Number of fin rays could be verified only in cleared and stained specimens. One 28 mm SL adult male specimen of N. bicornis from Brunei has two priapia (Fig. 8), a rare condition that has been reported previously as a developmental anomaly (Roberts, 1971 b: 417). Either one or both or neither of the priapia may have been functional in life; the first ctenactinium on the left side of the specimen illustrated here is incomplete either due to developmental arrest or damage. No parts of the specimen, other than those of reproductive morphology, are obviously duplicated. Such individuals may represent monozygotic twins — one sinistral and one dextral male — a hypothesis supported by the observation that sinistral and dextral males have been collected in about equal numbers (see FMNH material, above). A 215 bp fragment of the mitochondrial cytochrome c oxidase subunit 1 (COI), the DNA barcode (Ward et al., 2005), for N. bicornis from Thailand was sequenced as part of a study by Sparks & Smith (2004).	en	Parenti, Lynne R. (2014): A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bulletin of Zoology 62: 175-187, DOI: 10.5281/zenodo.4504094
