In later stages the pelvic bud turns into a skinfold with a thicker epidermis and abundant vascular plexuses, and then it disappears. When viewed from the side, it appears columnar. Subordo: Whippomorpha Infraordo: Eucynodontia There is no dorsal fin or dorsal ridge on the broad back. They begin life in freezing sea water in spring often in heavy sea ice. Eastern Canada. Among river dolphins, the Amazon River dolphin (Inia geoffrensis), lives in the large lakes and tributaries of the Amazon and Orinoco Basins. Mammal Species of the World – A Taxonomic and Geographic Reference . Much smaller than the right and bowhead whales (<7 m), it is slender, with a moderately arched mouthline.

The inter-calving interval averages about three years in this species, longer than for most other species of whales.

Cladus: Probainognathia The head represents only about one-quarter of the total length, and there is a short falcate dorsal fin set behind mid-back. Subregnum: Eumetazoa The pygmy right whale (Caperea marginata) is only found in the Southern Hemisphere. They are brownish-gray to black in color. Balaena in Mammal Species of the World.

Their only function is to allow insertion of smooth muscles related to the genital apparatus, and noticeably the m. ischiocavernosus (in both sexes) and the m. retractor penis (only in males). Cladus: Craniata The white portions of the pattern around the tail and on the flukes increase in extent with age. The presence/absence of callosities and coloration differences should make it easy to distinguish them. Right and bowhead whales are large whales, reaching up to 18 m in length and over 100,000 kg weight. Cladus: Sphenacodontia Adults can be 19 m in body length and exceed 80 metric tons in mass; however, some individuals may have exceeded 24 m and 100 metric tons based on observations by Inuit hunters and credible Yankee whaling records. Figure 3.75. North Atlantic right whales are skim-feeders—they swim along slowly with their mouth slightly agape, filtering out small invertebrates such as copepods from the water. The axillary girth may be more than half the total length. The population identity of right whales seen on rare occasions off Iceland and Greenland is unclear. Superordo: Boreoeutheria Young are born after a pregnancy of about a year in winter (mostly from December to March) on subtropical breeding grounds, nowadays primarily off the coasts of Florida and Georgia. Most bowheads accumulate distinctive, permanent marks on their backs, perhaps resulting from contact with sea ice or the sea floor when feeding. These include: the thickest blubber, thickest skin, greatest longevity, longest baleen, lowest body core temperatures, and proportionally the largest head of any cetacean (George et al., 1993; Haldiman and Tarpley, 1993). Superordo: Laurasiatheria Cladus: Synapsida Strictly northern, Arctic species are the closely related narwhal and beluga (both of which are tooted whales) and the bowhead, which is the only baleen whale that resides in the Arctic year round. Balaena is a genus of cetacean (whale) in the family Balaenidae. Classis: Mammalia (2006). Supercohort: Theria As such, three species of right whales are now recognized: E. japonica, E. glacialis, and E. australis, respectively. They can be aerially active, sometimes fluke-slapping and breaching repeatedly, and they generally raise their flukes before a deep dive.

The single species in this family, the pygmy right whale of the temperate Southern Hemisphere, is poorly known.

Cladus: Prozostrodontia North Atlantic right whales from two populations primarily inhabit temperate and subpolar waters of the North Atlantic Ocean. All Delphinidae of the genus Cephalorhynchus live in temperate waters of the Southern Hemisphere. The fringes of these plates are very fine, reflecting the small prey taken by this species. The right whales are among the stockiest of all whales.

Cladus: Mammaliaformes The head constitutes over a third of the bulk of the body, and the baleen may reach lengths of 4 m (no other whale has baleen longer than 2.8 m) with 230–360 plates on each side of the mouth, making the capacious mouth quite possibly the largest of any animal ever.

The North Atlantic right whale has a massive head that can be one-fourth to one-third of its body length. The evidence appears to support this hypothesis, although other functions cannot be ruled out.