Author: Bleeker, 1852
Diagnostic Features:
Snout rounded in dorsoventral view; gill slits short, 0.8 to 1.3 times eye length in adults; mouth broadly arched and very short, its length 31 to 43% of its width; lower jaw rounded at symphysis; ends of upper labial furrows extend in front of rear corners of eyes; no toothless space at midlines of jaws; upper anterolateral teeth with smooth mesial edges and very short cusps; lower anterolateral teeth with short, slender, unhooked cusps, and no cusplets; lower crown feet and roots deeply arched, giving teeth an inverted Y shape; lower teeth not protruding when mouth is closed; tooth row counts 25 to 34/37 to 43, 6 to 20 more lower rows than uppers; dorsal and pelvic fins and ventral caudal lobe strongly falcate; second dorsal height 3/5 or more of first dorsal height.
Remarks:
Whitley (1931:334) proposed Negogaleus as a replacement name for Hemigaleus, on the erroneous assumption that Hemigaleus is a junior homonym of Hemigalea Blainville, 1837 and Hemigalus Jourdain, 1837 in mammals (Viverridae), but under the present International Code of Zoological Nomenclature Hemigaleus is valid (Compagno, 1979).
Hemigaleus and its synonym Negogaleus have at one time or another included a total of nine species (balfouri, brachygnathus, longicaudatus, machlani, macrostoma, microstoma, pectoralis, pingi, and tengi). Under the revision by Compagno (1979), three of these fall in Paragaieus (longicaudatus, pectoralis and tengi), two (balfouri and macrostoma) in Chaenogaleus, one (pingi) in Triakis (as a synonym of T. scyllium), leaving three in Hemigaleus: H. brachygnathus Chu, 1960, H. machlani Herre, 1929, and H. microstoma Bleeker, 1852.
The account of the Chinese H. brachygnathus by Chu et al. (1963) and Bessednov (1964), when compared with specimens and data of Hemigaleus microstoma from Java, Singapore, and Thailand (including the surviving syntype), strongly suggests that Chu's species is a synonym of H. microstoma (see also Compagno, 1979). It is difficult to determine if H. machlani is a valid species from its brief, uniilustrated account (the holotype is unfortunately lost; J.A.F. Garrick, pers. comm.), but dentitional characters and its falcate pectoral fins and white-tipped dorsal fins suggest that the species was based on H. microstoma. However, no Philippine specimens of Hemigaleus or hemigaleids were available for examination.
Only one species is currently recognized in the genus Hemigaleus, H. microstoma. However, Stevens and Cuthbert (1983) noted that the Australian representative of this species, termed Negogaleus microstoma by Whitley (1939, 1940) and subsequent writers (surprisingly, Whitley did not propose a new name for this shark), differs consistantly in vertebral counts, coloration (with black dorsal fin tips instead of white ones), and tooth counts from typical H. microstoma as described by Compagno (1979). In addition, Compagno (1979) noted that Indian and Sri Lankan H. microstoma examined by him differ from typical members of the species in having somewhat higher vertebral counts. Whether these differences represent populational differences within a species or indicate that more than one species of Hemigaleus is involved remains to be seen. What is necessary is adeguate collections of Hemigaleus from almost all the areas where these sharks occur, and sampling in littleknown areas of the Indo-West Pacific to determine if they occur there.