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Pakicetids have long thin legs, with relatively short hands and feet which suggest that they were poor swimmers. [1] To compensate for that, their bones are unusually thick (osteosclerotic), which is probably an adaptation to make the animal heavier to counteract the buoyancy of the water. [7]
Female beaked whales' teeth are hidden in the gums and are not visible, and most male beaked whales have only two short tusks. Narwhals have vestigial teeth other than their tusk, which is present on males and 15% of females and has millions of nerves to sense water temperature, pressure and salinity.
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.
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 ]
Baleen whales have two flippers on the front, near the head. Like all mammals, baleen whales breathe air and must surface periodically to do so. Their nostrils, or blowholes, are situated at the top of the cranium. Baleen whales have two blowholes, as opposed to toothed whales which have one.
One of the diagnostic characteristics of artiodactyls is the double-pulley astragalus (heel bone), and palaeontologists, unconvinced by the data from the labs, set themselves out to find archaeocete single-pulley heel bones. Hind legs from three archaeocete species were recovered within a few years, among them those of Rodhocetus ...
Examples include the legs of a centipede, the maxillary and labial palps of an insect, and the spinous processes of successive vertebrae in a vertebrate's backbone. Male and female reproductive organs are homologous if they develop from the same embryonic tissue, as do the ovaries and testicles of mammals, including humans. [citation needed]
Unlike all later cetaceans, it had four fully functional long legs. Pakicetus had a long snout; a typical complement of teeth that included incisors, canines, premolars, and molars; a distinct and flexible neck; and a very long and robust tail. As in most land mammals, the nose was at the tip of the snout. [5]