click for previous page - 130 - 4. ORDER PRISTIOPHORIFORMES - SAW SHARKS Order Pristiophoriformes Compagno, 1973c, J.Linn.Soc.(Zool.), 53 suppl. 1. Synonymy : Order Asterospondyli: Gill, 1893 (in part). Order Euselachii, Suborder Galei: Jordan, 1923 (in part). Order Euselachii, Suborder Squaloidei: Blot, 1969 (in part). Suborder Galei: Gill, 1872 (in part). Suborder Plagiostomi Tectospondyli: Hasse, 1879 (in part). Order Pristiophorida: Fowler, 1969. Order Pristiophorae: Smith, 1949. Order Pristiophori: Whitley, 1940. Order Pristiophoriformes: Berg & Svedovidov, 1955; Patterson, 1967; Lindberg, 1971; Rass & Lindberg, 1971; Applegate, 1974; Chu & Wen, 1979. Suborder Pristiophorina: Matsubara, 1955. Suborder Pristiophoroidea: Bigelow & Schroeder, 1948. Suborder Pristiophoroidei: Nelson, 1976. Order Squalea, Suborder Squalida: White, 1936, 1937 (in part). Suborder Squali: Gill, 1862 (in part). Order Squaliformes, Suborder Squaloidei: Berg, 1940 (in part); Arambourg & Bertin, 1958. Suborder Squaliformes: Goodrich, 1909 (in part); Bertin, 1939 (in part), Budker & Whitehead, 1971 (in part). Order and Suborder Squaloidea: Schultz & Stern, 1948 (in part). Suborder Squaloidea: Romer, 1945, 1966 (in part); Norman, 1966 (in part). "Division" Squaloidei: Regan, 1906 (in part). "Group" Squaloidei: Garman, 1913 (in part). Suborder Squaloidei: Engelhardt, 1913 (in part). Order Squatinae: Fowler, 1941 (in part). Diagnostic Features: Trunk somewhat depressed but not greatly flattened and raylike. Head somewhat depressed but not expanded laterally; 5 or 6 pairs of gill slits present on sides of head, with the posteriormost in front of pectoral fin origins; spiracles present and very large, just behind and above level of eyes; nostrils without barbels, nasoral grooves or circumnarial grooves, separate from mouth, anterior nasal flaps short and not reaching mouth; eyes on dorsal surface of head, without nictitating lower eyelids; snout very long and greatly depressed, forming a sawlike blade with lateral denticles and a pair of long rostral barbels on its ventral surface well in front of the nostrils; mouth small, arched but short, behind eyes; labial furrows greatly reduced, at mouth cornets only; teeth weakly differentiated along the jaws, without enlarged anterior or posterior teeth and without a gap or small intermediate teeth between anterior and lateral teeth in the upper jaw. Two spineless dorsal fins present, the first with its origin over the interspace between the pectoral and pelvic bases; pectoral fins moderately large, not expanded and raylike, without triangular anterior lobes that cover the gill slits; pelvic fins small, with vent continuous with their inner margins; anal fin absent; caudal fin with a moderately long dorsal lobe but with ventral lobe absent; vertebral axis elevated into the dorsal caudal lobe. Intestinal valve of spiral type. 4.1 FAMILY PRISTIOPHORIDAE Bleeker, 1859 PRISTIOP Family Pristiophoroidei Bleeker, 1859, Act.Soc.Sci.Ind.Neerl., 4(3):xii. Synonymy : Family Pliotremidae Jordan, 1923. FAO Names: En - Saw sharks; Fr - Requins scie; Sp - Tiburones sierra. Field Marks : Long, flat snout with lateral sawteeth and ventral barbels, two spineless dorsal fins and no anal fin. Habitat, Distribution and Biology : Sawsharks are little-known temperate and tropical benthic and epibenthic inhabitants of the continental and insular shelves and upper slopes from close inshore to at least 915 m depth. Temperate sawsharks are found in shallow bays and estuaries down to offshore sand and gravel banks at modest depths, but one tropical species is a deepwater slope inhabitant at 640 m and below. The sawshark family is presently confined to the western North Atlantic in the vicinity of the Bahamas, the southeastern Atlantic and western Indian Ocean from the western Cape, South Africa, to southern Mozambique, apparently the Arabian Sea (where an undescribed species may occur), and the western Pacific off Japan, the Koreas, China, the Philippines and Australia. Fossil finds indicate that sawsharks were formerly more widespread, in the eastern Pacific and eastern North Atlantic. Sawsharks are small and very slender, with a maximum total length of about 137 cm. Several sawsharks are abundant where they occur, and are found in large schools or feeding aggregations. Despite their abundance, their habits are poorly known. At least one species shows segregation by depth within populations, with adults in deeper water than young. Sawsharks are ovoviviparous, and may have litters of 7 to 17 large young that are 28 to 35 cm long at birth. Apparently sawshark fetuses gain nutrients primarily from their large yolk sacks, which are resorbed just before birth. Apparently the large lateral rostral teeth erupt before birth in sawsharks, but to prevent injury to the mother these large teeth lie flat against the rostrum in fetuses until after birth. Smaller teeth erupt between the large ones after birth. - 131 - Food habits of sawsharks are poorly known, but their prey includes small fishes, crustaceans and squids. The long rostral barbels may have taste sensors, that these sharks trail along the bottom like those of sturgeons (Acipenseridae) and catfishes (Siluriformes) to locate prey. The long, rather delicate rostrum has lateral line and ampullal sensors for vibration and electrolocation, like a paddlefish (Polyodontidae) snout. The lateral rostral teeth, flat snout and head, enlarged occipital condyles, and specialized cervical vertebrae of sawsharks are evident modifications that allow these sharks to use their rostra as offensive weapons to kill their prey and possibly stir up bottom sediments to rouse prey organisms, but unlike the batoid sawfishes (Pristidae) this behaviour has not been observed, probably because sawsharks apparently have not been kept in captivity with any success (unlike sawfishes) and have not been studied underwater where they occur. The very short jaws and long oral and gill cavities of sawsharks suggest that they are capable of suddenly sucking prey into their mouths. Because of their small size and small, cuspidate teeth sawsharks are considered to be inoffensive to people (unlike large sawfishes which have occasionally injured and even killed bathers and may be a hazard to fishermen when caught in nets and on line gear). The rostra] teeth of sawsharks are sharp as needles though apparently nontoxic, so that these fishes should be handled with care to prevent puncture wounds on one's limbs. Interest to Fisheries : Considerable fisheries for sawsharks have occurred off southern Australia. They are taken and used in the western North Pacific to some extent, but details are sketchy. Sawsharks are commonly taken in the southwestern Indian Ocean off South Africa and southern Mozambique, but may be little utilized there. Sawsharks are caught in bottom trawls, and used fresh for human consumption. Remarks : Arrangement of this family follows Springer & Bullis (1959). 6 pairs of gill slits Key to Genera and Species 1a. Six pairs of gill openings (Fig. la). Larger rostral teeth serrated (Fig. 2) ................... Pliotrema warreni 1b. Five pairs of gill openings (Fig. 1b). Larger rostral teeth smooth (Pristiophorus) a. Pliotrema 5 pairs of gill slits 2a. Lateral trunk denticles largely tri- cuspidate. Preoral snout longer, about 31 to 32% of total length (Fig. 3) .......................... Pristioph orus schroederi 2b. Lateral trunk denticles largely uni- b. Pristiophorus Fig. 1 cuspidate. Preoral snout less than 30% of total length 3a. Rostrum relatively short and broad, distance from rostral tip to barbels much greater than distance from barbels to mouth. Dorsal and pectoral fins partially naked in large specimens (Fig. 4) .... Pristiophorus nudipinnis Pliotrema warreni Fig. 2 dorsal view Pristiophorus schroederi Fig.3 dorsal view Pristiophorus nudipinnis Fig. 4 - 132 - 3b. Rostrum long and narrower, distance from rostral tip to barbels about equal or slightly greater than distance from bar- bels to mouth. Dorsal and pectoral fins covered with denticles in large speci- a. dorsal view mens (Figs 5a,b) ......................... Pristiophorus cirratus Pristiophorus japonicus Pristiophorus cirratus lateral view b. Pristiophorus japonicus Fig. 5 Pliotrema Regan, 1906 PRISTIOP Plio Genus : Pliotrema Regan, 1906a, Ann.Natal Mus., 1(1):1. Type Species : Pliotrema warreni Regan, 1906, by monotypy. Synonymy : None. Diagnostic Features : Six pairs of gill slits. Large rostral sawteeth with posterior serrations. Teeth with prominent transverse ridges on basal ledges. Pliotrema warreni Regan, 1906 PRISTIOP PIio 1 Pliotrema warreni Regan, 1906a, Ann.Natal Mus., 1(1):1, pl. 1. Syntypes: British Museum (Natural History), BMNH 1905.6.8.9 is one of two specimens, each 750 mm total length. Type Locality: Two localities in South Africa given, Natal, 73 m depth, and False Bay, Cape of Good Hope. Synonymy : None. FAO Names : En - Sixgill sawshark; Fr - Requin scie flutian; Sp - Tiburón sierra del Cabo. teeth of saw barbel underside of head Field Marks : Six pairs of gill slits, sawlike snout with barbels. Diagnostic Features : See genus. upper and lower tooth - 133 - Geographical Distribution : Temperate and subtropical waters of the western Indian Ocean: Distribution centred on the south- eastern Cape coast of South Africa, but ranging from False Bay to central Natal and southern Mozambique. Habitat and Biology : A common benthic and epibenthic shark of the continental shelf and upper slope at depths of 60 to at least 430 m. It is most