Passage: C. longimanus' most distinguishing characteristics are its long, wing-like pectoral and dorsal fins. The fins are significantly larger than most other shark species, and are conspicuously rounded. The shark's nose is rounded and its eyes are circular, with nictitating membranes.C. longimanus has a 'typical', although somewhat flattened requiem shark body, often with a mildly humpbacked aspect. It is bronze, brown, bluish, or grey dorsally (the colour varies by region), and white ventrally (although it may occasionally have a yellow tint). The oceanic whitetip shark is a medium-sized requiem shark. The largest specimen ever caught measured 4 m (13 ft), an exceptionally large size considering few specimens are known to exceed a length of 3 m (9.8 ft). The maximum reported weight is 170 kg (370 lb). The female is typically larger than the male by 10 cm (3.9 in). Males attain sexual maturity at 1.7 to 1.9 m (5.6 to 6.2 ft) and females about 1.8 to 2.0 m (5.9 to 6.6 ft). In the Gulf of Mexico in the 1950s, the mean weight of oceanic whitetip sharks was 86.4 kg (190 lb). In the 1990s, the sharks of the species from the same area averaged only 56.1 kg (124 lb).Most of its fins (dorsal, pectoral, pelvic, and caudal) have white tips (juvenile specimens and some adults may lack these). Along with white tips, the fins may be mottled, and young specimens can have black marks. A saddle-like marking may be apparent between first and second dorsal fins. The shark has several kinds of teeth. Those in the mandible (lower jaw) have a thin, serrated tip and are relatively small and triangular (somewhat fang-like). Between 13 and 15 teeth are on either side of the symphysis. The teeth in the upper jaw are triangular, but much larger and broader with entirely serrated edges— 14 or 15 occur along each side of the symphysis. The denticles lie flat and typically have between five and seven ridges.

Question: What distinguishes young specimen of oceanic whitetip sharks?
black marks