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Zoology Publications from Victoria University of Wellington—Nos. 76 and 77

Family Carcharhinidae

page 2

Family Carcharhinidae

DEFINITION: Head not expanded into a winglike blade. Eyes low on sides of head, situated on horizontal head rim, with subocular ridge absent. Eyes less than twice as long as high, often about as long as high. Nictitating lower eyelid internal in all growth stages from newborn to adult, with its edge more or less slanted. Edge of secondary lower eyelid strongly differentiated, continuous anteriorly and posteriorly with upper eyelid. Subocular pouch very deep, curving below eyeball, and lacking denticles on its outer surface. Spiracles absent, vestigial, or small, consistently present only in Galeocerdo. No nasoral grooves. Anterior nasal flaps not in the form of barbels. Large papillae absent from buccal cavity. Labial furrows more or less reduced; when upper ones are elongate, they are very shallow anteriorly. Labial cartilages usually present (absent in Scoliodon, in some species of Rhizoprionodon, and in Galeocerdo).

Disjunct monognathic heterodonty (as defined by Compagno, 1970, 1979) always present, with medials or alternates and usually lower symphysials being the tooth groups present. Upper symphysials, anteriors, laterals, and posteriors are also present in some genera. Tooth crown with basal ledge, basal groove, and transverse ridges reduced or absent; when present, transverse ridges never extend far onto tooth crown and cusp. Teeth more or less compressed, bladelike, sharp-edged, with strong primary cusp on most or all teeth. Teeth never in a pavement, except for posterior teeth of Lamiopsis. Tooth rows relatively few, less than 40/40 in most genera, but with Isogomphodon having up to 61/56 rows. Three or fewer tooth series functional in all genera except Lamiopsis, which has from 4 to 8 series of posteriors.

Upper precaudal pits always present, lower pits usually present but sometimes absent or indistinct. Denticles from dorsum below first dorsal fin with crowns usually about as wide as long or wider than long.

Pectoral fin plesodic, with its skeleton supporting distal web of fin and projecting at least 2/3 of pectoral anterior margin length into fin. Distal pectoral radials tapering, pointed, and elongated, the longest distal radials over twice as long as longest proximal radials.

Claspers without exorhipidia. Clasper siphons long, reaching at least to free rear tips of pectorals. Cover rhipidion very large, extending nearly or quite to clasper tip. Rhipidion present or absent, when present mostly or entirely concealed by cover rhipidion. Dorsal edges of clasper groove forming a short tube between hypopyle and apopyle, not fused dorsally. Pseudosiphons usually present and very large. Pseudoperae present or absent. Clasper denticles nodular, rounded, acuspidate, and acarinate (clasper terminology follows Compagno & Springer, 1971, and Compagno, 1979).

Midpoint of first dorsal base well anterior to midpoints of pelvic bases. First dorsal insertion usually well anterior to pelvic origins, but nearly or quite over them in Scoliodon and Triaenodon. First dorsal base less then half as long as dorsal caudal margin, not in the form of a low, rounded keel. Second dorsal not greatly larger than anal, but only slightly larger, subequal in size, or smaller.

Ventral lobe of caudal fin always present. Postventral caudal margin deeply notched and divided into upper and lower parts in all genera except Scoliodon, in which it is usually deeply concave and not subdivided. Lateral undulations or ripples present on dorsal caudal margin (absent in young specimens of a few genera). Caudal axis at an angle to body axis.

Cranium with rostral cartilages always fused together at their distal tips, forming a basinlike, platelike, or yokelike rostral node. Nasal capsules usually ovoid or elongated, with nasal apertures confined to their anteroventral surface (Fig. 1). Nasal capsules with ventral shelves separating ectethmoid chambers from exterior. page 3Posteroventral surface of each nasal capsule with an ectethmoid condyle that articulates with the orbital process of the palatoquadrate. Ectethmoid condyle always perforated medially by an ectethmoid foramen, which communicates with the ectethmoid chamber. A deep subethmoidal fossa present between ectethmoid condyles on the ventral surface of the cranium. No supraorbital crests connecting the separate preorbital and postorbital processes.

Levator palatoquadrati muscles greatly expanded, with their origins extending anterior to the postorbital processes into the orbits, and their bodies extending diagonally posterolaterally to their insertions on the palatoquadrates.

Vertebral centra with strong, solid, wedge-shaped intermedialia. Diagonal calcified lamellae present or absent. Notochordal canal restricted or blocked at apices of calcified double cones in vertebral centra of adults and subadults, at least.

Valvular intestine with a scroll valve.

Development usually viviparous as far as is known, but Galeocerdo apparently is ovoviviparous.