Author: Smith, 1837
Field Marks:
Very stocky, compressed scyliorhinids with conspicuous trilobate anterior nasal flaps that include prominent conical barbels, second dorsal fin much smaller than first, short labial furrows on both jaws, and bold colour patterns of horizontal bars or rows of dark spots.
Diagnostic Features:
Body not tadpole-shaped, very stout and rather compressed, tapering considerably to caudal fin; body firm and thick skinned, with well-calcified dermal denticles; stomach not inflatable; tail moderately short, length from vent to lower caudal origin between 1/2 and 3/5 of snout-vent length. Head slightly depressed, narrowly rounded and not wedge-shaped in lateral view; head short, less than 1/5 of total length in adults. Snout short, less than 3/4 of mouth width, thick, and slightly flattened, bluntly pointed in lateral view; snout not expanded laterally, rounded-parabolic in dorsoventral view; ampullal pores not greatly enlarged on snout; nostrils not enlarged, with incurrent and excurrent apertures only slightly open to exterior; anterior nasal flaps divided into three prominent lobes, a subangular medial lobe, elongated, pendulous lateral lobe, and a long conical barbel between them; anterior nasal flaps well separated from each other but with barbels falling short of mouth or reaching it; internarial space 0.6 to 0.8 times in nostril width; nasoral grooves absent; eyes dorsolateral on head, broad subocular ridges present below eyes; mouth broadly arched, moderately long, with lower symphysis somewhat behind upper so that upper teeth are well-exposed in ventral view; labial furrows present along both upper and lower jaws, these relatively short; uppers little expanded in front of mouth corners and falling well behind level of upper symphysis of mouth; branchial region not greatly enlarged, distance from spiracles to fifth gill slits 1/2 to 2/5 head length; gill slits lateral on head. Two dorsal fins present, with the second considerably smaller than the first; origin of first dorsal about over pelvic insertions; origin of second dorsal over the anal midbase; pectoral fins large, their width considerably greater than mouth width; inner margins of pelvic fins partly fused over claspers in adult males, forming a partial 'apron'; claspers very short, thick, and distally rounded, not extending behind the pelvic fin tips; anal fin moderately large but not greatly elongated, subequal to pelvic and first dorsal fins but much larger than second dorsal; anal base length 1.6 to 2.2 times that of second dorsal base; origin of anal well behind pelvic bases, and insertion separated from lower caudal origin by a space less than half as long as the anal base; caudal fin very short and broad, less than a fifth of total length in adults. No crest of denticles on the dorsal caudal margin; supraorbital crests present on cranium. Colour light grey with a striking variegated colour pattern of horizontal rows of dark spots or rosettes of spots and bars, or horizontal bars, on dorsal surface and sides of body.
Remarks:
Poroderma was without description until Garman's (1913) account of it, in which it was restricted to P. africanum and P. pantherinum and fully diagnosed and described. Earlier, Fowler (1908) had revived the genus for P. africanum and P. stellare (= Scyliorhinus stellaris), but did not distinguish it.
Poroderma is close to Scyliorhinus but differs in being generally stouter-bodied and more compressed, having smaller spaces between the anal and caudal fin, definite short upper labial furrows, and trilobate, deeply notched anterior nasal flaps, with the medial ridge expanded to a prominent conical barbel and flanked basally by a pair of lobes. At most, Scyliorhinus species have a low medial ridge with a posterior low point on the triangular anterior nasal flaps, which are not subdivided and do not have conspicuous barbels. Scyliorhinus species often have colour patterns that are variants on dorsal saddles and spots, while Poroderma has longitudinal dark stripes or lines of spots or rosettes of spots and bars. Poroderma bears a similar relationship to Scyliorhinus as does the squaloid Cirrhigaleus to its close relative Squalus.
Bigelow and Schroeder (1948) used the genus Conoporoderma for P. pantherinum and P. marleyi, stating that Poroderma and its type species P. africanum were properly placed in the genus Scyliorhinus. The writer follows the arrangement of Fowler (1934, 1941), Bass, D'Aubrey and Kistnasamy (1975) and Springer (1979), who include these three species in the genus Poroderma.