Author: Whitley, 1939
Diagnostic Features:
Body not tadpole-shaped, slender and cylindrical, tapering slightly to caudal fin; body firm and thick skinned, with well-calcified dermal denticles; stomach not inflatable; tail moderately long, length from vent to lower caudal origin about 2/3 to nearly equal snout-vent length. Head slightly depressed, narrowly pointed-rounded in lateral view and not wedge-shaped; head short, less than 1/5 of total length in adults; snout short to slightly elongated, less than 5/6 of mouth width, thick, and slightly flattened, bluntly pointed in lateral view; snout not expanded laterally, rounded-parabolic and slightly bell-shaped in dorsoventral view; ampullal pores not greatly enlarged on snout; nostrils of moderate size, with incurrent and excurrent apertures only partly open to exterior; anterior nasal flaps formed as triangular lobes, without barbels, well separate from each other and falling somewhat anterior to mouth; internarial space 0.6 to 1 times the nostril width; no nasoral grooves; eyes dorsolateral on head, narrow subocular ridges present below eyes; mouth angular to arched, moderately long, with lower symphysis well behind upper so that upper teeth are exposed in ventral view; labial furrows present along both upper and lower jaws, these short and ending well behind level of upper symphysis of mouth; branchial region not greatly enlarged, distance from spiracles to fifth gill slits about half the head length; gill slits lateral on head. Two dorsal fins present, about equal-sized; origin of first dorsal over or slightly behind the pelvic insertions; origin of second dorsal varies from about over the anal midbase to over the rearmost third of its base; anal fin moderately large but not greatly elongated, about as large as pelvic fins and larger than dorsals, its base length 1.4 to 1.8 times the second dorsal base; pectoral fins moderately large, their width about equal to or slightly greater than mouth width; inner margins of pelvic fins fused over claspers and forming an 'apron' in adult males; claspers moderately long to very long, fairly thick to slender, and distally blunt or pointed, extending about half of their lengths or more behind the pelvic fin tips; origin of anal far behind pelvic bases, and insertion separated from lower caudal origin by a broad space over half the anal base; caudal fin short and broad, less than a fifth of total length in adults. No crests of denticles on the caudal margins; supraorbital crests absent from cranium. Colour light to dark brown above, light below, with a simple colour pattern of scattered white or dark spots on the sides and dorsal surface, and sometimes dark spots on the underside of head.
Remarks:
Whitley (1939) named two new genera for Australian catsharks, Asembolus for Scyllium anale Ogilby, 1885, and Juncrus for Scyllium vincenti Zeitz, 1908. Fowler (1941) retained these species in the genus Halaelurus, but Whitley (1939, 1940) distinguished his genera by the basally fused pelvic inner margins in adult males, which form an 'apron' over the claspers. Apart from coloration, Whitley offered little to distinguish the two genera from each other. Springer (1979) revived Asymbolus and Juncrus, but distinguished them only by relative clasper length in males, very long and slender in Juncrus vincenti and shorter and thicker in Asymbolus analis; and by the form of the 'apron' over the claspers (Springer, 1979:96).
Recently, much new material of Asymbolus-Juncrus catsharks has been collected off Australia, and is being studied by Dr John Stevens and the writer. There are at least two undescribed species in this material, which confound Springer's generic criteria. There is an analis-like new species that has vincenti-like elongated claspers, and a vincentilike new species with analis-like short claspers. Comparison of analis-like catsharks with vincentilike species revealed little difference in the form of the pelvic 'apron' of adult males of various species, and suggests nothing of significance to separate these sharks in different genera. Hence the genus Juncrus is synonymized with Asymbolus (mentioned before Juncrus in Whitley, 1939:229).
From the spotted species of Halaelurus, Asymbolus species additionally differ in their much narrower and less flattened heads, their nearly lateral eyes, lateral (rather than dorsolateral) gill slits, and more narrowly parabolic, bluntly rounded snouts (broader, often angular and pointed snouts in spotted Halaelurus). Possibly these differences are only worthy of subgeneric ranking within Halaelurus, but Asymbolus is retained for the southern Australian spotted catsharks (which almost certainly form a natural, monophyletic group) until relationships of the Halaelurus species are clarified.
Springer (1979) noted that Tasmanian and Australian mainland A. analis may be distinct, the Tasmanian form being considerably smaller (adult male 37 cm, versus mainland males immature at up to 51 cm and adult at 55 cm). In examining Asymbolus material the writer has seen such small, analis-like specimens, as well as the larger analis proper (including the holotype). However, whatever the status of these small analis-like sharks, there is definitely a new analis-like species that differs from analis in having numerous small black spots on its body and the underside of its head, in having enlarged teeth in males, and in being smaller. This will be described by Dr John Stevens and the writer.
Springer (1979) also noted that vincenti material examined by him was heterogeneous, and, while including it in a single species, noted that more material was necessary to determine if it represented more than one species. Apparently an additional new species of vincenti-like catshark exists, separable from typical vincenti in having a much lighter ground colour, larger and fewer light spots, shorter, thicker, pointed claspers, and in being considerably smaller.