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The degree of calcification varies between species, with the sei whale having 14.5% hydroxyapatite, a mineral that coats teeth and bones, whereas minke whales have 1–4% hydroxyapatite. In most mammals, keratin structures, such as wool , air-dry, but aquatic whales rely on calcium salts to form on the plates to stiffen them. [ 58 ]
Whales have two flippers on the front, and a tail fin. These flippers contain four digits. Although whales do not possess fully developed hind limbs, some, such as the sperm whale and bowhead whale, possess discrete rudimentary appendages, which may contain feet and digits.
Beaked whales have several anatomical adaptations to deep diving: large spleens, livers, and body shape. Most cetaceans have small spleens. However, beaked whales have much larger spleens than delphinids, and may have larger livers, as well. These anatomical traits, which are important for filtering blood, could be adaptations to deep diving.
There are approximately 89 [8] living species split into two parvorders: Odontoceti or toothed whales (containing porpoises, dolphins, other predatory whales like the beluga and the sperm whale, and the poorly understood beaked whales) and the filter feeding Mysticeti or baleen whales (which includes species like the blue whale, the humpback ...
Whales and their relatives have a soft tissue flipper that encases most of the forelimb, and elongated digits with an increased number of phalanges. [9] Hyperphalangy is an increase in the number of phalanges beyond the plesiomorphic mammal condition of three phalanges-per-digit. [ 10 ]
Some whales, such as the bowhead whale, have baleen of differing lengths. Other whales, such as the gray whale, only use one side of their baleen. These baleen bristles are arranged in plates across the upper jaw of whales. Depending on the species, a baleen plate can be 0.5 to 3.5 m (1.6 to 11.5 ft) long, and weigh up to 90 kg (200 lb).
The dorsal end of the ribs are remarkably thin and almost fail to make contact with the transverse processes. The reduced tail (or sacrocaudal region) features a vestigial pelvis and small chevron bones. [18] The flippers have four digits. The lungs and heart are relatively small, which suggests that the pygmy right whale is not a deep diver.
Toothed whales range in size from the 4.5 ft (1.4 m) and 120 lb (54 kg) vaquita to the 20 m (66 ft) and 55 t (61-short-ton) sperm whale. Overall, they tend to be dwarfed by their relatives, the baleen whales (Mysticeti). Several species have sexual dimorphism, with the females being larger than the males.