Proscyllium Hilgendorf, 1904

3.3.2 | Genus Proscyllium Hilgendorf, 1904 View in CoL

Synonymy: Proscyllium (subgenus of Scyllium ) Hilgendorf, 1904: 39 ( type species Proscyllium habereri Hilgendorf, 1904 , by monotypy); Compagno, 1984: 376; Nakaya in Masuda et al., 1984: 5; Compagno, 1988; LK. Calliscyllium Tanaka, 1912: 171 ( type species Calliscyllium venustum Tanaka, 1912 , by original designation, and monotypic).

Species: Monotypic genus comprised only of Proscyllium habereri (Figure 11).

Diagnosis: Proscylliid sharks with males adult at 428 – 565 mm L T, females at about 521 – 695 mm L T; monotypic. Head narrow and rather short, length about 16% – 18% of total length. Fifth gill opening half length of third gill opening, or less. Nostril width 1.7 – 2.2 times internarial width. Anterior nasal flaps very large, reaching nearly to upper symphysis (Figure 6c); posterior nasal flaps large; margins of anterior and posterior nasal flaps entire. Sexual heterodonty present, adult males mostly with three cusps, with median cusp taller; females with mostly five cusps, with median cusp lower (Figure 7b); tooth file counts 46 – 62/49 – 59. Length of head and trunk from snout tip to vent 39% – 42% of total length. Body slender, caudal peduncle not F I G U R E 5 Ctenacis magnificum from the Andaman Sea (fresh images):

(a) lateral view, adult male 440 mm L T

(not retained); (b) lateral view, female

510 mm L T (not retained; GenBank accession PP198923); (c) dorsal view,

female 510 mm L T (not retained;

GenBank accession PP198923).

compressed. Lateral trunk denticles of adults very narrow, with acute medial cusp and strong lateral cusps; two median ridges on crowns, parallel for most of their length; ectodermal pits barely evident, restricted to anteriormost portion of crown (Figure 8c,d). Distance between pectoral and pelvic bases greater than head length. Claspers of adult males very large, extending far posterior to free rear tips of pelvic fins; dorsal edges of clasper groove fused together between apopyle and hypopyle; cover rhipidion very small; exorhipidion with highly differentiated clasper hooks on its distal edge (see Figures 3 and 4 in Nakaya, 1983). First dorsal origin well posterior to pectoral free rear tip. Length of first dorsal fin from origin to free rear tip 1.8 – 2.7 in interdorsal space. Postanal space between anal insertion and lower caudal origin 1.3 – 1.5 times as long as anal base. Anal origin slightly anterior to second dorsal origin, anal insertion well anterior to second dorsal insertion. Caudal fin short, not tapelike, length of dorsal caudal margin 17% – 21% of total length.

Internal carotid foramina of cranium located relatively close together, the distance between them about twice distance between each internal carotid foramen and their adjacent stapedial foramen; anterior fontanelle relatively narrow, about as wide as it is long; edge of sphenopterotic ridge nearly parallel to longitudinal axis of cranium in dorsal view (Figure 1e,f). Total vertebral counts 146 – 168, DP counts 62 – 71, MP counts 24.8% – 26.9%, DP counts 42.4% – 45.2%, and DC counts 29.1% – 32.2% of total counts. DP/MP ratios 1.6 – 1.8. Spiral intestinal valve with eight or nine turns. Color pattern of small to large dark spots, sometimes light spots, indistinct dark saddles, and a light ground color.

Distribution: Known only from the northern Western Pacific (Figure 10).